Biomarkers
ISSN: 1354-750X (Print) 1366-5804 (Online) Journal homepage: http://www.tandfonline.com/loi/ibmk20
Reproducibility of cardiac biomarkers response to prolonged treadmill exercise Ye Tian, Jinlei Nie, Keith P. George & Chuanye Huang To cite this article: Ye Tian, Jinlei Nie, Keith P. George & Chuanye Huang (2014) Reproducibility of cardiac biomarkers response to prolonged treadmill exercise, Biomarkers, 19:2, 114-120 To link to this article: http://dx.doi.org/10.3109/1354750X.2014.880855
Published online: 23 Jan 2014.
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Date: 12 September 2015, At: 22:36
http://informahealthcare.com/bmk ISSN: 1354-750X (print), 1366-5804 (electronic) Biomarkers, 2014; 19(2): 114–120 ! 2014 Informa UK Ltd. DOI: 10.3109/1354750X.2014.880855
RESEARCH ARTICLE
Reproducibility of cardiac biomarkers response to prolonged treadmill exercise Ye Tian1, Jinlei Nie2, Keith P. George3, and Chuanye Huang4 China Institute of Sport Science, Beijing, China, 2School of Physical Education and Sports, Macao Polytechnic Institute, Macao, China, 3Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK, and 4College of Sports Science, Shanghai University of Sport, Shanghai, China Abstract
Keywords
We examined the reproducibility of alterations in cardiac biomarkers after two identical bouts of prolonged exercise in young athletes. Serum high-sensitivity cardiac troponin T (hs-cTnT) and N-terminal pro-brain natriuretic peptide (NT-proBNP) levels were assessed before and after exercise. Significant rises in median hs-cTnT and NT-proBNP occurred in both trials. While the absolute changes in hs-cTnT were smaller after trial 2, the pattern of change was similar and the delta scores were significantly related. However, the change in NT-proBNP was not correlated between trials. The hs-cTnT release demonstrates some consistency after exercise although the blunted hc-cTnT response requires further study.
Cardiac function, endurance run, highly sensitive cardiac troponin T, N-terminal pro-B-type natriuretic peptide
Introduction Acute bouts of endurance exercise may induce a minor and temporary reduction in left ventricular (LV) function (Oxborough et al., 2010; Shave et al., 2008) as well as the release of cardiac-specific biomarkers, such as cardiac troponins (cTnT/cTnI) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) (Nie et al., 2011a; Scharhag et al., 2008a; Shave et al., 2010). To date, there is no consensus as to the clinical relevance of such findings and whether such alterations are likely to impact upon sports performance or athlete health (Shave et al., 2010). An important part of the impact of these changes is whether post-exercise biomarker release and LV function change is a consistent and repeatable phenomenon. The information will be useful for clinicians evaluating athletes after endurance exercise events who present with cardiac biomarker elevation. Somewhat surprisingly very few studies have determined whether exercise-induced release of cardiac biomarkers and/or functional change is repeatable events or sporadic (random) responses (Middleton et al., 2007a; Sahlen et al., 2008; Scharhag et al., 2006). Some evidence suggests that post-exercise cTnT (Sahlen et al., 2008) and NT-proBNP (Sahlen et al., 2008; Scharhag et al., 2006) release is consistent after similar exercise bouts but Scharhag et al. (2006) and Middleton et al. (2007a,b) reported that the post-exercise release of cTn was not consistent after repeated endurance exercise bouts. Given
History Received 9 November 2013 Revised 29 December 2013 Accepted 4 January 2014 Published online 23 January 2014
that the limited data available is contradictory, various cTn assays have been used and the fact that in some studies significant periods of time (12 months) separated repeated exercise bouts (Middleton et al., 2007a; Sahlen et al., 2008), this particular facet of post-exercise cTn release requires further evaluation. Few studies have assessed the patterns of change in LV function in response to repeated bouts of exercise. Middleton et al. (2007a,b) provided some insight in two very different formats. In a group of runners performing repeated 3-h runs on consecutive days, there was consistent evidence of a reduction in LV diastolic filling each day but evidence of a progressive decrease in LV systolic function, suggesting a cumulative effect of exercise (Middleton et al., 2007b). Likewise, Middleton et al. (2007a) observed similar decreases in the early to atrial (E:A) ratio of trans-mitral Doppler filling velocities after two marathon runs. Some caution is warranted, however, as the runs were performed 12 months apart. Consequently, we investigated the effects of two identical laboratory-based treadmill runs, separated by three weeks, on blood high sensitivity (hs)-cTnT and NT-proBNP as well as indices of LV systolic function and diastolic filling in healthy young male runners. We hypothesize that changes in these parameters represent reproducible phenomena.
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Materials and methods Subjects
Address for correspondence: Ye Tian, China Institute of Sport Science, 11 Tiyuguan Road, Dongcheng District, Beijing 100061, China. Tel: 8610-8718 2528. Fax: 86-10-8718 2600. E-mail: [email protected]
Ten healthy male recreational runners were recruited for this study by open invitation at local running clubs. Table 1 summarizes their physical, fitness and training characteristics.
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DOI: 10.3109/1354750X.2014.880855
Table 1. Characteristics of subjects (Mean ± SD [Range], n ¼ 10). Age (yr) Height (cm) Mass (kg) BMI (kg m2) SBP (mmHg) DBP (mmHg) 1 1 VO2max (ml kg min ) HRmax (beats min1) Training years (yr) Week training volume (km) Day training volume (km)
20.4 ± 5.4 174 ± 9 61.8 ± 11.3 20.1 ± 2.0 117 ± 10 64 ± 6 56.6 ± 5.7 191 ± 6 2.4 ± 0.9 68.4 ± 33.3 13.1 ± 3.6
[14.6–27.9] [160–189] [42.7–81.2] [16.7–24.2] [105–133] [53–71] [48.0–65.0] [178.0–199.0] [0.9–3.6] [30.0–126.0] [10.0–20.0]
BMI, Body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure; VO2max, maximum oxygen consumption; HRmax, maximum heart rate.
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Leipzig, Germany). Exercise heart rate (HR) was measured using an HR monitor (Polar RS800CX, Kempele, Finland) at five-second intervals. Exercise was continued to volitional _ 2 max and HRmax were exhaustion. In the present study, VO recorded as the highest 30-s average values during the test. Thvent was defined as the point at which minute ventilation (V_ E ) increased during exercise in a non-linear fashion or when the ventilatory equivalent for O2 began to rise without a concomitant rise in the ventilatory equivalent for CO2, i.e. the first ventilatory threshold (Cheatham et al., 2000). The Thvent and the corresponding treadmill running speed were independently identified by two co-authors (Cheatham et al., 2000; Fu et al., 2010; Tian et al., 2012).
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Fixed-time treadmill run None of the subjects had any clinical evidence or personal history of cardiovascular disease. All had a normal 12-lead electrocardiogram (ECG) and echocardiogram at rest, as assessed by a cardiologist. All procedures conformed to the Declaration of Helsinki and were approved by the local ethics committee. Written informed consent was obtained from all the participants and/or their parents or legal guardians.
Subsequent to a general warm-up, the subjects initially walked on the treadmill. The treadmill speed was then increased gradually; once the subject had reached their target running speed both timing and HR recording began. During the test, the subject was constantly aware of the time and distance covered. Water intake was allowed ad libitum.
Experimental design
Cardiac biomarker assessment
The study employed a repeated measures design with three laboratory visits. Anthropometric measurements as well as the assessment of aerobic capacity and treadmill running speed at ventilatory threshold (Thvent) were conducted at the initial laboratory visit. In the subsequent two trials (Trial 1 and Trial 2), subjects performed two identical 90-min constant-load treadmill runs with the intensity set at the running speed corresponding to 95% Thvent as determined at the initial laboratory visit. The two trials occurred at the same time of the day in an air-conditioned laboratory with the temperature and relative humidity set at 20 C and 50%, respectively. Trial 1 and 2 were separated by three weeks. All subjects were familiar with the selected running intensities and durations, which were similar to those used in their routine training. Subjects reported no changes in their training habits in the three-week study period between trials. Before each trial, the subject refrained from eating for at least two hours and from participating in strenuous physical activity for 48 h. The assessment of cardiac biomarkers, hemoglobin (Hb), hematocrit (Hct) and body mass was completed before each trial (PRE) and then immediately (POST), one-hour (POST-1) and three hours (POST-3) after each trial. The timing for POST-3 blood sample was in accordance with previous data suggesting a peak in hs-cTnT at c.3 h post exercise (Tian et al., 2012). LV function was assessed before (PRE) and 30 min after (POST) each exercise bout.
At each sample, 5 mL of venous blood was drawn from the antecubital vein using venous puncture with subjects in a sitting position. An aliquot of whole blood was obtained immediately for the determination of hemoglobin (Hb) and hematocrit (Hct) using an automated hematology flow cytometry analyzer (Ac Tdiff 2, Beckman Coulter, Inc., Fullerton, CA). The remaining blood was allowed to clot at room temperature for 45 min and then centrifuged at 2000 g for 20 min. Serum was drawn and stored at 80 C for later analysis of hs-cTnT and NT-proBNP. The new high-sensitive electrochemiluminescent immunoassay (ECLIA) based on electrochemiluminescence technology using an automated analyzer (Modular Analytics E170, Roche Diagnostics, Mannheim, Germany) was employed to measure hs-cTnT quantitatively. The measurement range of this assay is 3 to 10 000 ng L1. The 99th percentile cut-off concentration and the level at 10% coefficient of variation are 14 and 13 ng L1, respectively. Furthermore, intra-assay CVs were 5.7 and 0.5% at 22 and 2980 ng L1, respectively; inter-assay CVs were 3.0 and 1.4% at 21 and 3030 ng L1, respectively. NT-pro-BNP concentrations were determined using an Elecsys proBNP ECLIA on the Modular Analytics E170 analyzer (Roche Diagnostic, Mannheim, Germany), with an analytical range of 5 to 35 000 pg mL1, and intra-assay and inter-assay imprecision of 0.7 to 1.6% and 5.3 to 6.6%, respectively. The URL for NT-proBNP was set at 125 pg mL1 (Silver et al., 2004). All analyzers were calibrated with standard concentrations according to the manufacturer’s protocols. Results of hs-cTnT and NT-proBNP were corrected for percentage change in plasma volume (%DPV) (Dill & Costill, 1974; Knebel et al., 2009; Lippi et al., 2008). Subjects underwent 2D and pulsed-Doppler transthoracic echocardiographic imaging while in the left lateral decubitus position using a commercially available ultrasound system (GE LOGIQ Book XP, GE Healthcare, San Jose, CA)
Protocols and measurements Graded treadmill run The protocol for the graded treadmill (LE500CE, VIASYS Healthcare GmbH, Wuerzburg, Germany) running test in the first laboratory visit has been described previously (Fu et al., 2010; Tian et al., 2012). Ventilatory and metabolic data were recorded using an automated on-line metabolic measuring instrument (MetaLyzer 3B, CORTEX Biophysik GmbH,
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following the American Society of Echocardiography guidelines (Lang et al., 2005). LV internal dimension at enddiastole (LVIDd) and end-systole (LVIDs) were measured from an M-mode trace and global LV systolic function was represented by ejection fraction (EF) and stroke volume (SV) calculated using the Teicholz estimation method. LVIDd was reported as an indirect estimate of preload, and HR was also recorded at this point from a concomitant single lead ECG. The LV meridional wall stress (LVMWS) was estimated to represent afterload (Reichek et al., 1982). Blood pressure was measured using an automated blood pressure monitor (Microlife BP A100 Plus; Microlife AG, Shenzhen, China) that was validated according to the European Society of Hypertension International Protocol (Belghazi et al., 2007). Pulsed-wave Doppler recordings of mitral inflow including early (E) and atrial (A) peak mitral inflow velocities were completed, and the ratio E:A calculated. A minimum of three consecutive cardiac cycles were saved to digital archive and analyzed offline. A single experienced sonographer performed all scans, and a single experienced and blinded technician made all offline measurements. Statistical analysis The Kolmogorov–Smirnov test was used to evaluate the normality of the data. When data demonstrated a skewed distribution, log-transformation was applied. The two-way ANOVA with repeated measures was employed to examine the differences in cardiac biomarker, hemoconcentration and echocardiographic parameters across time points observed for both trials. Post-hoc analyses using Newman–Keuls were performed for cases in which the main effect was significant. The average exercise HR and percentage of HRmax, during Trial 1 and 2, and cardiac markers in PRE to peak postexercise changes (delta scores) between Trial 1 and Trial 2 were compared using paired Student’s t-test. Correlations between delta scores for Trial 1 and 2, as well as the relationship between PRE and post-exercise peak levels for cardiac biomarkers, were determined via Pearson’s productmoment bivariate correlation analysis. Statistical significance was assumed at a level of p50.05. Data analysis was performed using the statistical software package SPSS 11.5 (SPSS Inc., Chicago, IL).
Results The average HR and the percentage of HRmax in Trial 1 (165 ± 10 beats min1; 87%) were marginally but significantly (p50.05) higher than those during Trial 2 (161 ± 7 beats min1; 84%). %DPV was significantly reduced POST in both trials before returning to baseline at POST-1 in Trial 1 but rebounding significantly above baseline at POST-3 in Trial 2. Body mass was reduced significantly after both the trials but had recovered by POST-3 (Table 2). Cardiac biomarkers Because of the skewed distribution of the hs-cTnT and NT-pro-BNP data log-transformations were applied before ANOVA, t-test and correlation analysis. The Kolmogorov– Smirnov test demonstrated that log transformation resulted in a normal distribution of data.
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Table 2. Hemoglobin (Hb), hematocrit (Hct) and body mass (BM) across assessment points in both trials (n ¼ 10).
Hct (%) Trial 1 Trial 2 Hb (g dl1) Trial 1 Trial 2 %DPV Trial 1 Trial 2 BM (kg) Trial 1 Trial 2
PRE
POST
POST-1
POST-3
41.3 ± 3.1 41.3 ± 3.2
43.6 ± 3.0* 42.9 ± 3.2
41.1 ± 3.1 41.5 ± 3.0
40.4 ± 3.3 40.5 ± 3.3
13.8 ± 1.2 13.9 ± 1.2
14.5 ± 1.1* 14.4 ± 1.2
13.9 ± 1.1 13.8 ± 1.2
13.6 ± 1.2 13.5 ± 1.2*
– 0 ± 9.4
8.2 ± 4.2* 5.5 ± 12.7
0.1 ± 3.4 0 ± 8.6
60.3 ± 11.1* 60.9 ± 11.0*
60.8 ± 11.0* 61.8 ± 11.2
61.8 ± 11.3 62.3 ± 11.4
3.6 ± 6.5 4.1 ± 11.2* 61.9 ± 11.2 62.8 ± 11.4
PRE, POST, POST-1 and POST-3: before, immediately after, and one hour and 3 hours after each run, respectively; %DPV: the percentage change in plasma volume. *Significantly different from corresponding PRE value, p50.05.
All runners had normal baseline levels of hs-cTnT in both trials (Trial 1: median [range]; 5.0 [3.0–10.0]; Trial 2: 5.5 [2.8–11.9] ng L1). In both trials hs-cTnT rose significantly at POST (Trial 1: 11.4 [2.9–41.9]; Trial 2: 11.3 [6.0– 15.9] ng L1) and POST-1 (Trial 1: 23.7 [10.8–225.3]; Trial 2: 15.9 [7.2–46.4] ng L1), and remained elevated at POST-3 (Trial 1: 85.4 [14.5–630.0]; Trial 2: 34.8 [10.7–187.3] ng L1) (Figure 1A). The absolute increase in hs-cTnT was greater after Trial 1 than Trial 2 (p50.05). Post-exercise hs-cTnT concentrations exceeded the 99th percentile of 14 ng L1 in 100 and 90% of the athletes after Trial 1 and Trial 2, respectively. There was a significant correlation between delta hs-cTnT after both trials (Figure 2). Baseline NT-proBNP was similar prior to both trials. In both Trial 1 and 2 NT-pro-BNP was significantly increased from baseline (Trial 1: median [range]; 16.2 [5.0–41.5]; Trial 2: 14.6 [4.6–26.8] pg mL1) at POST (Trial 1: 31.7 [5.0–84.8]; Trial 2: 35.3 [10.4–70.5] pg mL1) and this did not return to baseline by POST-3 (Trial 1: 26.9 [5.4–65.0]; Trial 2: 28.2 [14.0–55.6] pg mL1) (Figure 1B). No single NT-pro-BNP concentration exceeded the URL. The delta change in NT-proBNP from baseline was not significantly correlated (Figure 3). Individual PRE hs-cTnT values did not predict exercise changes in either trial. The individual PRE values for NT-proBNP were significantly associated with the postexercise peak values in each trial (Trial 1, r ¼ 0.860; Trial 2, r ¼ 0.865, both p50.05). Echocardiographic data Although HR at the time of the POST assessment was significantly elevated both LVIDd and LVMWS were not altered (Table 3). SV and EF did not change following either run. Peak E was reduced, and peak A increased, to a similar extent, after both trials (p50.05) and consequently the E:A ratio was reduced after both runs (p50.05). The delta change in E:A from PRE to POST was highly reproducible from Trial 1 to Trial 2 (r ¼ 0.829, p50.05; Figure 4). The post-exercise reduction in E:A was not related to changes in HR. Finally, no association was observed between the changes in E:A and delta values of cardiac markers in either trial.
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Figure 3. Delta changes (PRE to peak post-exercise) in serum NT-proBNP in Trial 1 and Trial 2.
Table 3. Left ventricular function and loading before (PRE) and after (POST) each run trial in runners (n ¼ 10, mean ± SD). Trial 1 PRE
POST
Trial 2 PRE
POST
1
Figure 1. The median and interquartile range of Hs-cTnT (A) and NTproBNP (B) across assessment points in both trials (n ¼ 10). PRE, POST, POST-1 and POST-3: before, immediately after, and one hour and 3 h after each run, respectively; The horizontal dotted line a is the upper reference limit of hs-cTnT. *Trial 1 and Trial 2 significantly different from corresponding PRE value, p50.05. #Significantly different from corresponding Trial 1 value, p50.05.
Figure 2. Delta changes (PRE to peak post-exercise) in serum cardiac troponin T (hs-cTnT) in Trial 1 and Trial 2.
Discussion To our knowledge, this is the first study to evaluate the reproducibility of exercise-induced releases in cardiac biomarkers and altered left ventricular (LV) function in a
HR (beats min ) 57 ± 5 80 ± 8* 57 ± 7 74 ± 7* Loading LVIDd (cm) 5.2 ± 0.3 5.1 ± 0.4 5.2 ± 0.3 5.2 ± 0.3 LVMWS (g cm2) 46 ± 9 46 ± 11 52 ± 11 57 ± 13 Systolic function SV (mL beats1) 94 ± 13 86 ± 16 90 ± 9 86 ± 13 EF (%) 74 ± 5 71 ± 5 69 ± 5 67 ± 6 Diastolic filling E (cm s1) 90 ± 9 83 ± 4* 88 ± 9 82 ± 6* A (cm s1) 48 ± 6 55 ± 9* 48 ± 5 54 ± 6* E:A 1.89 ± 0.18 1.55 ± 0.20* 1.85 ± 0.17 1.53 ± 0.20* HR: heart rate; LVIDd: left ventricular internal dimension at enddiastole; LVMWS: left ventricular meridional wall stress; SV: stroke volume; EF: ejection fraction; E: peak early ventricular filling velocity; A: peak late ventricular filling velocity. *Significantly different from corresponding PRE value, p50.05.
Figure 4. Delta changes in the early and late atrial filling ratio (E.A) from PRE to POST in Trial 1 and Trial 2.
controlled laboratory-based setting. The major findings were that the hs-cTnT release was qualitatively similar, but quantitatively reduced after a second 90-min of endurance running. A reduction in LV diastolic filling was highly
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reproducible after the two exercise bouts. While NT-proBNP was raised after both exercise bouts there was no correlation in the change of scores from Trial 1 to 2. It is clear that the role of cardiac biomarkers in the management of acute coronary syndromes is vitally important, with clinical decisions being guided by biochemistry. Clinicians, therefore, should be fully aware of all the situations that may impact circulating cardiac biomarkers. Accordingly, it is important to understand the nature and magnitude of exercise-induced cardiac biomarker changes. An important aspect of this is whether post-exercise biomarker release is a consistent and repeatable or random phenomenon. The repeated assessment of exercise-induced biomarker release has been studied by a number of groups (Bonetti et al., 1996; Middleton et al., 2007a,b; Nie et al., 2011b; Sahlen et al., 2008; Scharhag et al., 2006, 2008b; Shave et al., 2004). The present study differs from and extends previous studies in several aspects. Firstly, in the present study, the exerciseinduced biomarkers releases were observed in two bouts of identical exercise in a controlled laboratory-based setting, while previous studies employed field-based competitions (Bonetti et al., 1996; Middleton et al., 2007a,b; Sahlen et al., 2008; Scharhag et al., 2008b). While ecologically valid, fieldbased exercise has made it difficult to control many factors such as the duration and intensity of effort and environmental conditions. Secondly, we evaluated changes of biomarkers 0– 3 h after exercise unlike other studies that examined values only immediately after exercise (Bonetti et al., 1996; Middleton et al., 2007a,b; Nie et al., 2011b; Sahlen et al., 2008; Scharhag et al., 2006). The timing for 3 h blood sample was important, as this was in accordance with our previous data suggesting a peak in hs-cTnT at c.3 h post exercise (Tian et al., 2012). The timing for immediately after exercise might be not enough to catch the peak cTnT release. hs-cTnT Although an increase in cTnT has been reported in multiple endurance exercise studies (Scharhag et al., 2008a; Shave et al., 2010), only one study has demonstrated that postexercise cTnT release is repeatable (Sahlen et al., 2008) although the two 30-km cross-country races were separated by three years. The current data confirms this study in a controlled setting with younger runners but contradicts the findings of Scharhag et al. (2006) and Middleton et al. (2007b). The reason for this discrepancy is not known, but may be related to the nature of the exercise stress, the research design employed, the relative control of the exercise environment and/or the method used for determination of cTnT. The hs-cTnT assay used in the current study is more precise and permits analyses of cTn concentrations that are 10-fold lower than determined in previous 3rd generation assays used in Scharhag et al. (2006) and Middleton et al. (2007b) studies. Despite the high correlation between hs-cTnT release after Trial 1 and 2, it is important to note that significantly lower levels of hs-TnT were detected after Trial 2 compared to Trial 1. Only three weeks had elapsed between Trials 1 and 2, during which time the subjects maintained their routine training. Consequently altered training status is an unlikely explanation of this difference. The standardized use of
Biomarkers, 2014; 19(2): 114–120
laboratory-based settings in the current study largely excludes the possibility that the effects of exercise duration, environment and dehydration caused a lower response in Trial 2. It is noteworthy that while the same external workload was completed in both trials, there was a slight drop in cardiovascular work (HR) during Trial 2. It is possible that the small drop in HR during Trial 2, potentially due to a treadmill running learning effect, could have contributed to a lower hs-cTnT response in Trial 2. This requires confirmation in further studies. Alternatively, this phenomenon could reflect a ‘‘repeated bout effect’’ similar to that observed with skeletal muscle damage after unaccustomed exercise (Hortobagyi & Denahan, 1989). While speculative at this point it is worth following-up with further research. The underlying mechanism(s) and clinical significance of exercise-induced hs-cTnT remain unclear. Our recent animal study demonstrated a temporal association between elevations of serum cTnT and myocardial oxidative stress after prolonged exercise (Nie et al., 2010), which supports the notion that an increase in the production of reactive oxygen species could lead to a membrane ‘‘insult’’ and hence cTnT release. It is well documented that endurance exercise naturally precipitates oxidative stress in healthy humans (Ji, 1995). In a similar study we have observed a rapid increase and then a decrease in hs-cTnT after exercise (Tian et al., 2012). These hs-cTnT kinetics are not what would be observed in a classical clinical presentation of elevated cTnT after a myocardial infarction (Wu et al., 1999). Together, these observations provide further support of a physiological substrate responsible for post-exercise cTnT release. NT-proBNP In the current study, athletes demonstrated a significant increase in NT-proBNP post-exercise, although in no instance did the values exceed the clinical cut-off (125 pg mL1). The small magnitude of NT-proBNP increase likely reflects the relatively limited hemodynamic stress of a 90-min exercise bout. Previous investigations have reported increases in NT-proBNP levels following prolonged exercise, and the magnitudes of increase have been related to duration of exercise (Scharhag et al., 2008a). The current study confirms, in a controlled laboratory setting, previous results from field-based experiments that show that baseline levels of NT-proBNP are an important determinant of the exercise response of this biomarker (Carranza-Garcia et al., 2011; Sahlen, 2008). Interestingly, while this point would logically suggest a reproducible increase in NT-proBNP after two identical exercise bouts, the correlation between delta NT-proBNP responses was not significant. This may reflect a range effect where correlation coefficients are likely small when the range of data compared is small. Alternatively, this could suggest a more labile baseline NT-proBNP in this group that determined the response specific to either Trial 1 or 2. Interestingly, in the current study, a high degree of intra-individual variability in blood volume change, reflected by %DPV, was observed between Trials 1 and 2, even though they took place at the same running velocity and duration in both trials. Whether the wide variations in blood volume changes between the two
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trials altered baseline and thus exercise NT-proBNP release cannot be conclusively determined within this study.
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future studies could include tissue Doppler and/or strain imaging, to allow the interrogation of segmental LV, right ventricular and atrial function.
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Cardiac function No reduction in LV contractility (EF) was noted in both trials. Middleton et al. (2006) reported that a transient decrease in systolic function may only be apparent following endurance exercise of 6 h duration. Hence, the exercise duration employed in the present study may have been too short to induce a significant decrease in LV systolic function. Previous data suggest that changes in LV filling post-exercise may be more consistent or appear earlier than changes in LV systolic function (George et al., 2004). Our study supports this contention and confirms the findings of Vanoverschelde et al. (1991), who observed a small but significant reduction in diastolic filling, even after moderately prolonged exercise. Importantly the reduction in E:A was highly reproducible after both bouts which confirms data from Middleton et al. (2007a), who demonstrated that the reduction in E:A following two marathons, separated by 12 months, was consistent. The cause(s) of these modest but consistent changes in LV diastolic filling velocities are not clearly understood. Diastolic filling parameters can be affected by changes in loading and HR (Oxborough et al., 2010) but their impact, in the current study, is limited. This suggests that changes in intrinsic LV relaxation and/or compliance may underpin the reduction in E:A in the current study but this requires further work. Changes in E:A were not associated with changes in hs-cTnT and thus it would seem that cardiac damage is not implicated in alterations in diastolic filling after prolonged exercise. Clinical implications and perspectives The elevation of hs-cTnT is a key part of the evaluation of acute coronary syndromes in clinical practice and clinicians should be aware of other factors that can be considered in the differential diagnosis of an elevated cTnT. Further, measurement of hs-cTnT after a symptom-limited exercise test improves the diagnostic evaluation of coronary artery disease when added to the results of the exercise test in stable chest pain subjects (Mouridsen et al., 2013). The current data describe an elevation in hs-cTnT release after 90 min of steady state exercise in adolescent–young adults. The individual variability in hs-cTnT release after prolonged exercise and the blunted response to a second, identical, bout of prolonged exercise are relevant in the assessment of athletes in clinical care scenarios. Qualitatively, our data support the concept that exercise-induced cardiac biomarker release and changes in LV function after prolonged exercise are not random or sporadic but in certain individuals. The findings may aid the development of understanding clinical significance of elevated cardiac biomarkers after exercise. Limitations We only studied male athletes with a relatively small sample size, and as such generalizability of the data is limited. Finally, due to logistical constraints we employed conventional M-mode and Doppler echocardiography to assess LV functional indices. Additional measures of cardiac function in
Conclusion Two 90-min constant-rate treadmill runs at an identical speed were performed by young, healthy athletes, separated by three weeks. Hs-cTnT release was qualitatively similar after both runs although the absolute increase after Trial 2 was somewhat blunted. NT-proBNP was significantly elevated, to the same level, after both runs but the release of NT-proBNP was not consistent within individual runners over the two trials. A reduction in E:A after both runs was highly reproducible but not related to changes in loading, HR or biomarker release. The findings of the present study were observed in a controlled laboratory-based setting and extend previous work derived from field-based competitions.
Acknowledgements The authors would like to express their thanks to Ping Hong, Baoxin Feng, Weiying Zhang, Peifang Zong and Wenyuan Shang for their excellent technical assistance. The cooperation of the subjects is greatly appreciated.
Declaration of interest The authors report no declarations of interest. The study was supported by a research grant from National Science and Technology Ministry of China (Study on the Key Factors in Potential Gold Medal Events for Elite Athletes, No. 2006BAK37B00).
References Belghazi J, El Feghali RN, Moussalem T, et al. (2007). Validation of four automatic devices for self-measurement of blood pressure according to the International Protocol of the European Society of Hypertension. Vasc Health Risk Manag 3:389–400. Bonetti A, Tirelli F, Albertini R, et al. (1996). Serum cardiac troponin T after repeated endurance exercise events. Int J Sports Med 17:259–62. Carranza-Garcia LE, George K, Serrano-Ostariz E, et al. (2011). Cardiac biomarker response to intermittent exercise bouts. Int J Sports Med 32:327–31. Cheatham CC, Mahon AD, Brown JD, Bolster DR. (2000). Cardiovascular responses during prolonged exercise at ventilatory threshold in boys and men. Med Sci Sports Exerc 32:1080–7. Dill DB, Costill DL. (1974). Calculation of percentage changes in volumes of blood, plasma, and red cells in dehydration. J Appl Physiol 37:247–8. Fu F, Nie J, George K, et al. (2010). Impact of a 21-km run on cardiac biomarkers in adolescent runners. J Exerc Sci Fit 8:61–6. George K, Whyte G, Stephenson C, et al. (2004). Postexercise left ventricular function and cTnT in recreational marathon runners. Med Sci Sports Exerc 36:1709–15. Hortobagyi T, Denahan T. (1989). Variability in creatine kinase: methodological, exercise, and clinically related factors. Int J Sports Med 10:69–80. Ji LL. (1995). Oxidative stress during exercise: implication of antioxidant nutrients. Free Radic Biol Med 18:1079–86. Knebel F, Schimke I, Schroeckh S, et al. (2009). Myocardial function in older male amateur marathon runners: assessment by tissue Doppler echocardiography, speckle tracking, and cardiac biomarkers. J Am Soc Echocardiogr 22:803–9. Lang RM, Bierig M, Devereux RB, et al. (2005). Recommendations for chamber quantification: a report from the American Society of Echocardiography’s Guidelines and Standards Committee and the Chamber Quantification Writing Group, developed in conjunction
Downloaded by [Stockholm University Library] at 22:36 12 September 2015
120
Y. Tian et al.
with the European Association of Echocardiography, a branch of the European Society of Cardiology. J Am Soc Echocardiogr 18:1440–63. Lippi G, Schena F, Salvagno GL, et al. (2008). Acute variation of estimated glomerular filtration rate following a half-marathon run. Int J Sports Med 29:948–51. Middleton N, Shave R, George K, et al. (2006). Left ventricular function immediately following prolonged exercise: a meta-analysis. Med Sci Sports Exerc 38:681–7. Middleton N, Shave R, George K, et al. (2007a). Altered left ventricular diastolic filling following a marathon is a reproducible phenomenon. Int J Cardiol 122:87–9. Middleton N, Shave R, George K, et al. (2007b). Impact of repeated prolonged exercise bouts on cardiac function and biomarkers. Med Sci Sports Exerc 39:83–90. Mouridsen MR, Nielsen OW, Pedersen OD, et al. (2013). Diagnostic value of exercise-induced changes in circulating high sensitive troponin T in stable chest pain patients. Biomarkers 18:726–33. Nie J, Close G, George KP, et al. (2010). Temporal association of elevations in serum cardiac troponin T and myocardial oxidative stress after prolonged exercise in rats. Eur J Appl Physiol 110:1299–303. Nie J, George KP, Tong TK, et al. (2011a). The influence of a halfmarathon race upon cardiac troponin T release in adolescent runners. Curr Med Chem 18:3452–6. Nie J, George KP, Tong TK, et al. (2011b). Effect of repeated endurance runs on cardiac biomarkers and function in adolescents. Med Sci Sports Exerc 43:2081–8. Oxborough D, Birch K, Shave R, George K. (2010). ‘‘Exercise-induced cardiac fatigue’’ – a review of the echocardiographic literature. Echocardiography 27:1130–40. Reichek N, Wilson J, St John SM, et al. (1982). Noninvasive determination of left ventricular end-systolic stress: validation of the method and initial application. Circulation 65:99–108. Sahlen A, Winter R, Lind B, et al. (2008). Magnitude, reproducibility, and association with baseline cardiac function of cardiac biomarker
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release in long-distance runners aged 4 or ¼55 years. Am J Cardiol 102:218–22. Scharhag J, George K, Shave R, et al. (2008a). Exercise-associated increases in cardiac biomarkers. Med Sci Sports Exerc 40:1408–15. Scharhag J, Meyer T, Auracher M, et al. (2008b). Exercise-induced increases in NT-proBNP are not related to the exercise-induced immune response. Br J Sports Med 42:383–5. Scharhag J, Urhausen A, Schneider G, et al. (2006). Reproducibility and clinical significance of exercise-induced increases in cardiac troponins and N-terminal pro brain natriuretic peptide in endurance athletes. Eur J Cardiovasc Prev Rehabil 13:388–97. Shave R, Baggish A, George K, et al. (2010). Exercise-induced cardiac troponin elevation: evidence, mechanisms, and implications. J Am Coll Cardiol 56:169–76. Shave R, Dawson E, Whyte G, et al. (2004). Effect of prolonged exercise in a hypoxic environment on cardiac function and cardiac troponin T. Br J Sports Med 38:86–8. Shave R, George K, Whyte G, et al. (2008). Postexercise changes in left ventricular function. the evidence so far. Med Sci Sports Exerc 40: 1393–9. Silver MA, Maisel A, Yancy CW, et al. (2004). BNP Consensus Panel 2004. A clinical approach for the diagnostic, prognostic, screening, treatment monitoring, and therapeutic roles of natriuretic peptides in cardiovascular diseases. Congest Heart Fail 10:1–30. Tian Y, Nie J, Huang C, George K. (2012). The kinetics of highly sensitive cardiac troponin T release after prolonged treadmill exercise in adolescent and adult athletes. J Appl Physiol 113:418–25. Vanoverschelde JL, Younis LT, Melin JA, et al. (1991). Prolonged exercise induces left ventricular dysfunction in healthy subjects. J Appl Physiol 70:1356–63. Wu AH, Apple FS, Gibler WB, et al. (1999). National Academy of Clinical Biochemistry Standards of Laboratory Practice: recommendations for the use of cardiac markers in coronary artery diseases. Clin Chem 45:1104–21.
ISSN: 1354-750X (Print) 1366-5804 (Online) Journal homepage: http://www.tandfonline.com/loi/ibmk20
Reproducibility of cardiac biomarkers response to prolonged treadmill exercise Ye Tian, Jinlei Nie, Keith P. George & Chuanye Huang To cite this article: Ye Tian, Jinlei Nie, Keith P. George & Chuanye Huang (2014) Reproducibility of cardiac biomarkers response to prolonged treadmill exercise, Biomarkers, 19:2, 114-120 To link to this article: http://dx.doi.org/10.3109/1354750X.2014.880855
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Date: 12 September 2015, At: 22:36
http://informahealthcare.com/bmk ISSN: 1354-750X (print), 1366-5804 (electronic) Biomarkers, 2014; 19(2): 114–120 ! 2014 Informa UK Ltd. DOI: 10.3109/1354750X.2014.880855
RESEARCH ARTICLE
Reproducibility of cardiac biomarkers response to prolonged treadmill exercise Ye Tian1, Jinlei Nie2, Keith P. George3, and Chuanye Huang4 China Institute of Sport Science, Beijing, China, 2School of Physical Education and Sports, Macao Polytechnic Institute, Macao, China, 3Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK, and 4College of Sports Science, Shanghai University of Sport, Shanghai, China Abstract
Keywords
We examined the reproducibility of alterations in cardiac biomarkers after two identical bouts of prolonged exercise in young athletes. Serum high-sensitivity cardiac troponin T (hs-cTnT) and N-terminal pro-brain natriuretic peptide (NT-proBNP) levels were assessed before and after exercise. Significant rises in median hs-cTnT and NT-proBNP occurred in both trials. While the absolute changes in hs-cTnT were smaller after trial 2, the pattern of change was similar and the delta scores were significantly related. However, the change in NT-proBNP was not correlated between trials. The hs-cTnT release demonstrates some consistency after exercise although the blunted hc-cTnT response requires further study.
Cardiac function, endurance run, highly sensitive cardiac troponin T, N-terminal pro-B-type natriuretic peptide
Introduction Acute bouts of endurance exercise may induce a minor and temporary reduction in left ventricular (LV) function (Oxborough et al., 2010; Shave et al., 2008) as well as the release of cardiac-specific biomarkers, such as cardiac troponins (cTnT/cTnI) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) (Nie et al., 2011a; Scharhag et al., 2008a; Shave et al., 2010). To date, there is no consensus as to the clinical relevance of such findings and whether such alterations are likely to impact upon sports performance or athlete health (Shave et al., 2010). An important part of the impact of these changes is whether post-exercise biomarker release and LV function change is a consistent and repeatable phenomenon. The information will be useful for clinicians evaluating athletes after endurance exercise events who present with cardiac biomarker elevation. Somewhat surprisingly very few studies have determined whether exercise-induced release of cardiac biomarkers and/or functional change is repeatable events or sporadic (random) responses (Middleton et al., 2007a; Sahlen et al., 2008; Scharhag et al., 2006). Some evidence suggests that post-exercise cTnT (Sahlen et al., 2008) and NT-proBNP (Sahlen et al., 2008; Scharhag et al., 2006) release is consistent after similar exercise bouts but Scharhag et al. (2006) and Middleton et al. (2007a,b) reported that the post-exercise release of cTn was not consistent after repeated endurance exercise bouts. Given
History Received 9 November 2013 Revised 29 December 2013 Accepted 4 January 2014 Published online 23 January 2014
that the limited data available is contradictory, various cTn assays have been used and the fact that in some studies significant periods of time (12 months) separated repeated exercise bouts (Middleton et al., 2007a; Sahlen et al., 2008), this particular facet of post-exercise cTn release requires further evaluation. Few studies have assessed the patterns of change in LV function in response to repeated bouts of exercise. Middleton et al. (2007a,b) provided some insight in two very different formats. In a group of runners performing repeated 3-h runs on consecutive days, there was consistent evidence of a reduction in LV diastolic filling each day but evidence of a progressive decrease in LV systolic function, suggesting a cumulative effect of exercise (Middleton et al., 2007b). Likewise, Middleton et al. (2007a) observed similar decreases in the early to atrial (E:A) ratio of trans-mitral Doppler filling velocities after two marathon runs. Some caution is warranted, however, as the runs were performed 12 months apart. Consequently, we investigated the effects of two identical laboratory-based treadmill runs, separated by three weeks, on blood high sensitivity (hs)-cTnT and NT-proBNP as well as indices of LV systolic function and diastolic filling in healthy young male runners. We hypothesize that changes in these parameters represent reproducible phenomena.
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1
Materials and methods Subjects
Address for correspondence: Ye Tian, China Institute of Sport Science, 11 Tiyuguan Road, Dongcheng District, Beijing 100061, China. Tel: 8610-8718 2528. Fax: 86-10-8718 2600. E-mail: [email protected]
Ten healthy male recreational runners were recruited for this study by open invitation at local running clubs. Table 1 summarizes their physical, fitness and training characteristics.
Cardiac biomarkers and exercise
DOI: 10.3109/1354750X.2014.880855
Table 1. Characteristics of subjects (Mean ± SD [Range], n ¼ 10). Age (yr) Height (cm) Mass (kg) BMI (kg m2) SBP (mmHg) DBP (mmHg) 1 1 VO2max (ml kg min ) HRmax (beats min1) Training years (yr) Week training volume (km) Day training volume (km)
20.4 ± 5.4 174 ± 9 61.8 ± 11.3 20.1 ± 2.0 117 ± 10 64 ± 6 56.6 ± 5.7 191 ± 6 2.4 ± 0.9 68.4 ± 33.3 13.1 ± 3.6
[14.6–27.9] [160–189] [42.7–81.2] [16.7–24.2] [105–133] [53–71] [48.0–65.0] [178.0–199.0] [0.9–3.6] [30.0–126.0] [10.0–20.0]
BMI, Body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure; VO2max, maximum oxygen consumption; HRmax, maximum heart rate.
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Leipzig, Germany). Exercise heart rate (HR) was measured using an HR monitor (Polar RS800CX, Kempele, Finland) at five-second intervals. Exercise was continued to volitional _ 2 max and HRmax were exhaustion. In the present study, VO recorded as the highest 30-s average values during the test. Thvent was defined as the point at which minute ventilation (V_ E ) increased during exercise in a non-linear fashion or when the ventilatory equivalent for O2 began to rise without a concomitant rise in the ventilatory equivalent for CO2, i.e. the first ventilatory threshold (Cheatham et al., 2000). The Thvent and the corresponding treadmill running speed were independently identified by two co-authors (Cheatham et al., 2000; Fu et al., 2010; Tian et al., 2012).
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Fixed-time treadmill run None of the subjects had any clinical evidence or personal history of cardiovascular disease. All had a normal 12-lead electrocardiogram (ECG) and echocardiogram at rest, as assessed by a cardiologist. All procedures conformed to the Declaration of Helsinki and were approved by the local ethics committee. Written informed consent was obtained from all the participants and/or their parents or legal guardians.
Subsequent to a general warm-up, the subjects initially walked on the treadmill. The treadmill speed was then increased gradually; once the subject had reached their target running speed both timing and HR recording began. During the test, the subject was constantly aware of the time and distance covered. Water intake was allowed ad libitum.
Experimental design
Cardiac biomarker assessment
The study employed a repeated measures design with three laboratory visits. Anthropometric measurements as well as the assessment of aerobic capacity and treadmill running speed at ventilatory threshold (Thvent) were conducted at the initial laboratory visit. In the subsequent two trials (Trial 1 and Trial 2), subjects performed two identical 90-min constant-load treadmill runs with the intensity set at the running speed corresponding to 95% Thvent as determined at the initial laboratory visit. The two trials occurred at the same time of the day in an air-conditioned laboratory with the temperature and relative humidity set at 20 C and 50%, respectively. Trial 1 and 2 were separated by three weeks. All subjects were familiar with the selected running intensities and durations, which were similar to those used in their routine training. Subjects reported no changes in their training habits in the three-week study period between trials. Before each trial, the subject refrained from eating for at least two hours and from participating in strenuous physical activity for 48 h. The assessment of cardiac biomarkers, hemoglobin (Hb), hematocrit (Hct) and body mass was completed before each trial (PRE) and then immediately (POST), one-hour (POST-1) and three hours (POST-3) after each trial. The timing for POST-3 blood sample was in accordance with previous data suggesting a peak in hs-cTnT at c.3 h post exercise (Tian et al., 2012). LV function was assessed before (PRE) and 30 min after (POST) each exercise bout.
At each sample, 5 mL of venous blood was drawn from the antecubital vein using venous puncture with subjects in a sitting position. An aliquot of whole blood was obtained immediately for the determination of hemoglobin (Hb) and hematocrit (Hct) using an automated hematology flow cytometry analyzer (Ac Tdiff 2, Beckman Coulter, Inc., Fullerton, CA). The remaining blood was allowed to clot at room temperature for 45 min and then centrifuged at 2000 g for 20 min. Serum was drawn and stored at 80 C for later analysis of hs-cTnT and NT-proBNP. The new high-sensitive electrochemiluminescent immunoassay (ECLIA) based on electrochemiluminescence technology using an automated analyzer (Modular Analytics E170, Roche Diagnostics, Mannheim, Germany) was employed to measure hs-cTnT quantitatively. The measurement range of this assay is 3 to 10 000 ng L1. The 99th percentile cut-off concentration and the level at 10% coefficient of variation are 14 and 13 ng L1, respectively. Furthermore, intra-assay CVs were 5.7 and 0.5% at 22 and 2980 ng L1, respectively; inter-assay CVs were 3.0 and 1.4% at 21 and 3030 ng L1, respectively. NT-pro-BNP concentrations were determined using an Elecsys proBNP ECLIA on the Modular Analytics E170 analyzer (Roche Diagnostic, Mannheim, Germany), with an analytical range of 5 to 35 000 pg mL1, and intra-assay and inter-assay imprecision of 0.7 to 1.6% and 5.3 to 6.6%, respectively. The URL for NT-proBNP was set at 125 pg mL1 (Silver et al., 2004). All analyzers were calibrated with standard concentrations according to the manufacturer’s protocols. Results of hs-cTnT and NT-proBNP were corrected for percentage change in plasma volume (%DPV) (Dill & Costill, 1974; Knebel et al., 2009; Lippi et al., 2008). Subjects underwent 2D and pulsed-Doppler transthoracic echocardiographic imaging while in the left lateral decubitus position using a commercially available ultrasound system (GE LOGIQ Book XP, GE Healthcare, San Jose, CA)
Protocols and measurements Graded treadmill run The protocol for the graded treadmill (LE500CE, VIASYS Healthcare GmbH, Wuerzburg, Germany) running test in the first laboratory visit has been described previously (Fu et al., 2010; Tian et al., 2012). Ventilatory and metabolic data were recorded using an automated on-line metabolic measuring instrument (MetaLyzer 3B, CORTEX Biophysik GmbH,
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following the American Society of Echocardiography guidelines (Lang et al., 2005). LV internal dimension at enddiastole (LVIDd) and end-systole (LVIDs) were measured from an M-mode trace and global LV systolic function was represented by ejection fraction (EF) and stroke volume (SV) calculated using the Teicholz estimation method. LVIDd was reported as an indirect estimate of preload, and HR was also recorded at this point from a concomitant single lead ECG. The LV meridional wall stress (LVMWS) was estimated to represent afterload (Reichek et al., 1982). Blood pressure was measured using an automated blood pressure monitor (Microlife BP A100 Plus; Microlife AG, Shenzhen, China) that was validated according to the European Society of Hypertension International Protocol (Belghazi et al., 2007). Pulsed-wave Doppler recordings of mitral inflow including early (E) and atrial (A) peak mitral inflow velocities were completed, and the ratio E:A calculated. A minimum of three consecutive cardiac cycles were saved to digital archive and analyzed offline. A single experienced sonographer performed all scans, and a single experienced and blinded technician made all offline measurements. Statistical analysis The Kolmogorov–Smirnov test was used to evaluate the normality of the data. When data demonstrated a skewed distribution, log-transformation was applied. The two-way ANOVA with repeated measures was employed to examine the differences in cardiac biomarker, hemoconcentration and echocardiographic parameters across time points observed for both trials. Post-hoc analyses using Newman–Keuls were performed for cases in which the main effect was significant. The average exercise HR and percentage of HRmax, during Trial 1 and 2, and cardiac markers in PRE to peak postexercise changes (delta scores) between Trial 1 and Trial 2 were compared using paired Student’s t-test. Correlations between delta scores for Trial 1 and 2, as well as the relationship between PRE and post-exercise peak levels for cardiac biomarkers, were determined via Pearson’s productmoment bivariate correlation analysis. Statistical significance was assumed at a level of p50.05. Data analysis was performed using the statistical software package SPSS 11.5 (SPSS Inc., Chicago, IL).
Results The average HR and the percentage of HRmax in Trial 1 (165 ± 10 beats min1; 87%) were marginally but significantly (p50.05) higher than those during Trial 2 (161 ± 7 beats min1; 84%). %DPV was significantly reduced POST in both trials before returning to baseline at POST-1 in Trial 1 but rebounding significantly above baseline at POST-3 in Trial 2. Body mass was reduced significantly after both the trials but had recovered by POST-3 (Table 2). Cardiac biomarkers Because of the skewed distribution of the hs-cTnT and NT-pro-BNP data log-transformations were applied before ANOVA, t-test and correlation analysis. The Kolmogorov– Smirnov test demonstrated that log transformation resulted in a normal distribution of data.
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Table 2. Hemoglobin (Hb), hematocrit (Hct) and body mass (BM) across assessment points in both trials (n ¼ 10).
Hct (%) Trial 1 Trial 2 Hb (g dl1) Trial 1 Trial 2 %DPV Trial 1 Trial 2 BM (kg) Trial 1 Trial 2
PRE
POST
POST-1
POST-3
41.3 ± 3.1 41.3 ± 3.2
43.6 ± 3.0* 42.9 ± 3.2
41.1 ± 3.1 41.5 ± 3.0
40.4 ± 3.3 40.5 ± 3.3
13.8 ± 1.2 13.9 ± 1.2
14.5 ± 1.1* 14.4 ± 1.2
13.9 ± 1.1 13.8 ± 1.2
13.6 ± 1.2 13.5 ± 1.2*
– 0 ± 9.4
8.2 ± 4.2* 5.5 ± 12.7
0.1 ± 3.4 0 ± 8.6
60.3 ± 11.1* 60.9 ± 11.0*
60.8 ± 11.0* 61.8 ± 11.2
61.8 ± 11.3 62.3 ± 11.4
3.6 ± 6.5 4.1 ± 11.2* 61.9 ± 11.2 62.8 ± 11.4
PRE, POST, POST-1 and POST-3: before, immediately after, and one hour and 3 hours after each run, respectively; %DPV: the percentage change in plasma volume. *Significantly different from corresponding PRE value, p50.05.
All runners had normal baseline levels of hs-cTnT in both trials (Trial 1: median [range]; 5.0 [3.0–10.0]; Trial 2: 5.5 [2.8–11.9] ng L1). In both trials hs-cTnT rose significantly at POST (Trial 1: 11.4 [2.9–41.9]; Trial 2: 11.3 [6.0– 15.9] ng L1) and POST-1 (Trial 1: 23.7 [10.8–225.3]; Trial 2: 15.9 [7.2–46.4] ng L1), and remained elevated at POST-3 (Trial 1: 85.4 [14.5–630.0]; Trial 2: 34.8 [10.7–187.3] ng L1) (Figure 1A). The absolute increase in hs-cTnT was greater after Trial 1 than Trial 2 (p50.05). Post-exercise hs-cTnT concentrations exceeded the 99th percentile of 14 ng L1 in 100 and 90% of the athletes after Trial 1 and Trial 2, respectively. There was a significant correlation between delta hs-cTnT after both trials (Figure 2). Baseline NT-proBNP was similar prior to both trials. In both Trial 1 and 2 NT-pro-BNP was significantly increased from baseline (Trial 1: median [range]; 16.2 [5.0–41.5]; Trial 2: 14.6 [4.6–26.8] pg mL1) at POST (Trial 1: 31.7 [5.0–84.8]; Trial 2: 35.3 [10.4–70.5] pg mL1) and this did not return to baseline by POST-3 (Trial 1: 26.9 [5.4–65.0]; Trial 2: 28.2 [14.0–55.6] pg mL1) (Figure 1B). No single NT-pro-BNP concentration exceeded the URL. The delta change in NT-proBNP from baseline was not significantly correlated (Figure 3). Individual PRE hs-cTnT values did not predict exercise changes in either trial. The individual PRE values for NT-proBNP were significantly associated with the postexercise peak values in each trial (Trial 1, r ¼ 0.860; Trial 2, r ¼ 0.865, both p50.05). Echocardiographic data Although HR at the time of the POST assessment was significantly elevated both LVIDd and LVMWS were not altered (Table 3). SV and EF did not change following either run. Peak E was reduced, and peak A increased, to a similar extent, after both trials (p50.05) and consequently the E:A ratio was reduced after both runs (p50.05). The delta change in E:A from PRE to POST was highly reproducible from Trial 1 to Trial 2 (r ¼ 0.829, p50.05; Figure 4). The post-exercise reduction in E:A was not related to changes in HR. Finally, no association was observed between the changes in E:A and delta values of cardiac markers in either trial.
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Figure 3. Delta changes (PRE to peak post-exercise) in serum NT-proBNP in Trial 1 and Trial 2.
Table 3. Left ventricular function and loading before (PRE) and after (POST) each run trial in runners (n ¼ 10, mean ± SD). Trial 1 PRE
POST
Trial 2 PRE
POST
1
Figure 1. The median and interquartile range of Hs-cTnT (A) and NTproBNP (B) across assessment points in both trials (n ¼ 10). PRE, POST, POST-1 and POST-3: before, immediately after, and one hour and 3 h after each run, respectively; The horizontal dotted line a is the upper reference limit of hs-cTnT. *Trial 1 and Trial 2 significantly different from corresponding PRE value, p50.05. #Significantly different from corresponding Trial 1 value, p50.05.
Figure 2. Delta changes (PRE to peak post-exercise) in serum cardiac troponin T (hs-cTnT) in Trial 1 and Trial 2.
Discussion To our knowledge, this is the first study to evaluate the reproducibility of exercise-induced releases in cardiac biomarkers and altered left ventricular (LV) function in a
HR (beats min ) 57 ± 5 80 ± 8* 57 ± 7 74 ± 7* Loading LVIDd (cm) 5.2 ± 0.3 5.1 ± 0.4 5.2 ± 0.3 5.2 ± 0.3 LVMWS (g cm2) 46 ± 9 46 ± 11 52 ± 11 57 ± 13 Systolic function SV (mL beats1) 94 ± 13 86 ± 16 90 ± 9 86 ± 13 EF (%) 74 ± 5 71 ± 5 69 ± 5 67 ± 6 Diastolic filling E (cm s1) 90 ± 9 83 ± 4* 88 ± 9 82 ± 6* A (cm s1) 48 ± 6 55 ± 9* 48 ± 5 54 ± 6* E:A 1.89 ± 0.18 1.55 ± 0.20* 1.85 ± 0.17 1.53 ± 0.20* HR: heart rate; LVIDd: left ventricular internal dimension at enddiastole; LVMWS: left ventricular meridional wall stress; SV: stroke volume; EF: ejection fraction; E: peak early ventricular filling velocity; A: peak late ventricular filling velocity. *Significantly different from corresponding PRE value, p50.05.
Figure 4. Delta changes in the early and late atrial filling ratio (E.A) from PRE to POST in Trial 1 and Trial 2.
controlled laboratory-based setting. The major findings were that the hs-cTnT release was qualitatively similar, but quantitatively reduced after a second 90-min of endurance running. A reduction in LV diastolic filling was highly
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reproducible after the two exercise bouts. While NT-proBNP was raised after both exercise bouts there was no correlation in the change of scores from Trial 1 to 2. It is clear that the role of cardiac biomarkers in the management of acute coronary syndromes is vitally important, with clinical decisions being guided by biochemistry. Clinicians, therefore, should be fully aware of all the situations that may impact circulating cardiac biomarkers. Accordingly, it is important to understand the nature and magnitude of exercise-induced cardiac biomarker changes. An important aspect of this is whether post-exercise biomarker release is a consistent and repeatable or random phenomenon. The repeated assessment of exercise-induced biomarker release has been studied by a number of groups (Bonetti et al., 1996; Middleton et al., 2007a,b; Nie et al., 2011b; Sahlen et al., 2008; Scharhag et al., 2006, 2008b; Shave et al., 2004). The present study differs from and extends previous studies in several aspects. Firstly, in the present study, the exerciseinduced biomarkers releases were observed in two bouts of identical exercise in a controlled laboratory-based setting, while previous studies employed field-based competitions (Bonetti et al., 1996; Middleton et al., 2007a,b; Sahlen et al., 2008; Scharhag et al., 2008b). While ecologically valid, fieldbased exercise has made it difficult to control many factors such as the duration and intensity of effort and environmental conditions. Secondly, we evaluated changes of biomarkers 0– 3 h after exercise unlike other studies that examined values only immediately after exercise (Bonetti et al., 1996; Middleton et al., 2007a,b; Nie et al., 2011b; Sahlen et al., 2008; Scharhag et al., 2006). The timing for 3 h blood sample was important, as this was in accordance with our previous data suggesting a peak in hs-cTnT at c.3 h post exercise (Tian et al., 2012). The timing for immediately after exercise might be not enough to catch the peak cTnT release. hs-cTnT Although an increase in cTnT has been reported in multiple endurance exercise studies (Scharhag et al., 2008a; Shave et al., 2010), only one study has demonstrated that postexercise cTnT release is repeatable (Sahlen et al., 2008) although the two 30-km cross-country races were separated by three years. The current data confirms this study in a controlled setting with younger runners but contradicts the findings of Scharhag et al. (2006) and Middleton et al. (2007b). The reason for this discrepancy is not known, but may be related to the nature of the exercise stress, the research design employed, the relative control of the exercise environment and/or the method used for determination of cTnT. The hs-cTnT assay used in the current study is more precise and permits analyses of cTn concentrations that are 10-fold lower than determined in previous 3rd generation assays used in Scharhag et al. (2006) and Middleton et al. (2007b) studies. Despite the high correlation between hs-cTnT release after Trial 1 and 2, it is important to note that significantly lower levels of hs-TnT were detected after Trial 2 compared to Trial 1. Only three weeks had elapsed between Trials 1 and 2, during which time the subjects maintained their routine training. Consequently altered training status is an unlikely explanation of this difference. The standardized use of
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laboratory-based settings in the current study largely excludes the possibility that the effects of exercise duration, environment and dehydration caused a lower response in Trial 2. It is noteworthy that while the same external workload was completed in both trials, there was a slight drop in cardiovascular work (HR) during Trial 2. It is possible that the small drop in HR during Trial 2, potentially due to a treadmill running learning effect, could have contributed to a lower hs-cTnT response in Trial 2. This requires confirmation in further studies. Alternatively, this phenomenon could reflect a ‘‘repeated bout effect’’ similar to that observed with skeletal muscle damage after unaccustomed exercise (Hortobagyi & Denahan, 1989). While speculative at this point it is worth following-up with further research. The underlying mechanism(s) and clinical significance of exercise-induced hs-cTnT remain unclear. Our recent animal study demonstrated a temporal association between elevations of serum cTnT and myocardial oxidative stress after prolonged exercise (Nie et al., 2010), which supports the notion that an increase in the production of reactive oxygen species could lead to a membrane ‘‘insult’’ and hence cTnT release. It is well documented that endurance exercise naturally precipitates oxidative stress in healthy humans (Ji, 1995). In a similar study we have observed a rapid increase and then a decrease in hs-cTnT after exercise (Tian et al., 2012). These hs-cTnT kinetics are not what would be observed in a classical clinical presentation of elevated cTnT after a myocardial infarction (Wu et al., 1999). Together, these observations provide further support of a physiological substrate responsible for post-exercise cTnT release. NT-proBNP In the current study, athletes demonstrated a significant increase in NT-proBNP post-exercise, although in no instance did the values exceed the clinical cut-off (125 pg mL1). The small magnitude of NT-proBNP increase likely reflects the relatively limited hemodynamic stress of a 90-min exercise bout. Previous investigations have reported increases in NT-proBNP levels following prolonged exercise, and the magnitudes of increase have been related to duration of exercise (Scharhag et al., 2008a). The current study confirms, in a controlled laboratory setting, previous results from field-based experiments that show that baseline levels of NT-proBNP are an important determinant of the exercise response of this biomarker (Carranza-Garcia et al., 2011; Sahlen, 2008). Interestingly, while this point would logically suggest a reproducible increase in NT-proBNP after two identical exercise bouts, the correlation between delta NT-proBNP responses was not significant. This may reflect a range effect where correlation coefficients are likely small when the range of data compared is small. Alternatively, this could suggest a more labile baseline NT-proBNP in this group that determined the response specific to either Trial 1 or 2. Interestingly, in the current study, a high degree of intra-individual variability in blood volume change, reflected by %DPV, was observed between Trials 1 and 2, even though they took place at the same running velocity and duration in both trials. Whether the wide variations in blood volume changes between the two
Cardiac biomarkers and exercise
DOI: 10.3109/1354750X.2014.880855
trials altered baseline and thus exercise NT-proBNP release cannot be conclusively determined within this study.
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future studies could include tissue Doppler and/or strain imaging, to allow the interrogation of segmental LV, right ventricular and atrial function.
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Cardiac function No reduction in LV contractility (EF) was noted in both trials. Middleton et al. (2006) reported that a transient decrease in systolic function may only be apparent following endurance exercise of 6 h duration. Hence, the exercise duration employed in the present study may have been too short to induce a significant decrease in LV systolic function. Previous data suggest that changes in LV filling post-exercise may be more consistent or appear earlier than changes in LV systolic function (George et al., 2004). Our study supports this contention and confirms the findings of Vanoverschelde et al. (1991), who observed a small but significant reduction in diastolic filling, even after moderately prolonged exercise. Importantly the reduction in E:A was highly reproducible after both bouts which confirms data from Middleton et al. (2007a), who demonstrated that the reduction in E:A following two marathons, separated by 12 months, was consistent. The cause(s) of these modest but consistent changes in LV diastolic filling velocities are not clearly understood. Diastolic filling parameters can be affected by changes in loading and HR (Oxborough et al., 2010) but their impact, in the current study, is limited. This suggests that changes in intrinsic LV relaxation and/or compliance may underpin the reduction in E:A in the current study but this requires further work. Changes in E:A were not associated with changes in hs-cTnT and thus it would seem that cardiac damage is not implicated in alterations in diastolic filling after prolonged exercise. Clinical implications and perspectives The elevation of hs-cTnT is a key part of the evaluation of acute coronary syndromes in clinical practice and clinicians should be aware of other factors that can be considered in the differential diagnosis of an elevated cTnT. Further, measurement of hs-cTnT after a symptom-limited exercise test improves the diagnostic evaluation of coronary artery disease when added to the results of the exercise test in stable chest pain subjects (Mouridsen et al., 2013). The current data describe an elevation in hs-cTnT release after 90 min of steady state exercise in adolescent–young adults. The individual variability in hs-cTnT release after prolonged exercise and the blunted response to a second, identical, bout of prolonged exercise are relevant in the assessment of athletes in clinical care scenarios. Qualitatively, our data support the concept that exercise-induced cardiac biomarker release and changes in LV function after prolonged exercise are not random or sporadic but in certain individuals. The findings may aid the development of understanding clinical significance of elevated cardiac biomarkers after exercise. Limitations We only studied male athletes with a relatively small sample size, and as such generalizability of the data is limited. Finally, due to logistical constraints we employed conventional M-mode and Doppler echocardiography to assess LV functional indices. Additional measures of cardiac function in
Conclusion Two 90-min constant-rate treadmill runs at an identical speed were performed by young, healthy athletes, separated by three weeks. Hs-cTnT release was qualitatively similar after both runs although the absolute increase after Trial 2 was somewhat blunted. NT-proBNP was significantly elevated, to the same level, after both runs but the release of NT-proBNP was not consistent within individual runners over the two trials. A reduction in E:A after both runs was highly reproducible but not related to changes in loading, HR or biomarker release. The findings of the present study were observed in a controlled laboratory-based setting and extend previous work derived from field-based competitions.
Acknowledgements The authors would like to express their thanks to Ping Hong, Baoxin Feng, Weiying Zhang, Peifang Zong and Wenyuan Shang for their excellent technical assistance. The cooperation of the subjects is greatly appreciated.
Declaration of interest The authors report no declarations of interest. The study was supported by a research grant from National Science and Technology Ministry of China (Study on the Key Factors in Potential Gold Medal Events for Elite Athletes, No. 2006BAK37B00).
References Belghazi J, El Feghali RN, Moussalem T, et al. (2007). Validation of four automatic devices for self-measurement of blood pressure according to the International Protocol of the European Society of Hypertension. Vasc Health Risk Manag 3:389–400. Bonetti A, Tirelli F, Albertini R, et al. (1996). Serum cardiac troponin T after repeated endurance exercise events. Int J Sports Med 17:259–62. Carranza-Garcia LE, George K, Serrano-Ostariz E, et al. (2011). Cardiac biomarker response to intermittent exercise bouts. Int J Sports Med 32:327–31. Cheatham CC, Mahon AD, Brown JD, Bolster DR. (2000). Cardiovascular responses during prolonged exercise at ventilatory threshold in boys and men. Med Sci Sports Exerc 32:1080–7. Dill DB, Costill DL. (1974). Calculation of percentage changes in volumes of blood, plasma, and red cells in dehydration. J Appl Physiol 37:247–8. Fu F, Nie J, George K, et al. (2010). Impact of a 21-km run on cardiac biomarkers in adolescent runners. J Exerc Sci Fit 8:61–6. George K, Whyte G, Stephenson C, et al. (2004). Postexercise left ventricular function and cTnT in recreational marathon runners. Med Sci Sports Exerc 36:1709–15. Hortobagyi T, Denahan T. (1989). Variability in creatine kinase: methodological, exercise, and clinically related factors. Int J Sports Med 10:69–80. Ji LL. (1995). Oxidative stress during exercise: implication of antioxidant nutrients. Free Radic Biol Med 18:1079–86. Knebel F, Schimke I, Schroeckh S, et al. (2009). Myocardial function in older male amateur marathon runners: assessment by tissue Doppler echocardiography, speckle tracking, and cardiac biomarkers. J Am Soc Echocardiogr 22:803–9. Lang RM, Bierig M, Devereux RB, et al. (2005). Recommendations for chamber quantification: a report from the American Society of Echocardiography’s Guidelines and Standards Committee and the Chamber Quantification Writing Group, developed in conjunction
Downloaded by [Stockholm University Library] at 22:36 12 September 2015
120
Y. Tian et al.
with the European Association of Echocardiography, a branch of the European Society of Cardiology. J Am Soc Echocardiogr 18:1440–63. Lippi G, Schena F, Salvagno GL, et al. (2008). Acute variation of estimated glomerular filtration rate following a half-marathon run. Int J Sports Med 29:948–51. Middleton N, Shave R, George K, et al. (2006). Left ventricular function immediately following prolonged exercise: a meta-analysis. Med Sci Sports Exerc 38:681–7. Middleton N, Shave R, George K, et al. (2007a). Altered left ventricular diastolic filling following a marathon is a reproducible phenomenon. Int J Cardiol 122:87–9. Middleton N, Shave R, George K, et al. (2007b). Impact of repeated prolonged exercise bouts on cardiac function and biomarkers. Med Sci Sports Exerc 39:83–90. Mouridsen MR, Nielsen OW, Pedersen OD, et al. (2013). Diagnostic value of exercise-induced changes in circulating high sensitive troponin T in stable chest pain patients. Biomarkers 18:726–33. Nie J, Close G, George KP, et al. (2010). Temporal association of elevations in serum cardiac troponin T and myocardial oxidative stress after prolonged exercise in rats. Eur J Appl Physiol 110:1299–303. Nie J, George KP, Tong TK, et al. (2011a). The influence of a halfmarathon race upon cardiac troponin T release in adolescent runners. Curr Med Chem 18:3452–6. Nie J, George KP, Tong TK, et al. (2011b). Effect of repeated endurance runs on cardiac biomarkers and function in adolescents. Med Sci Sports Exerc 43:2081–8. Oxborough D, Birch K, Shave R, George K. (2010). ‘‘Exercise-induced cardiac fatigue’’ – a review of the echocardiographic literature. Echocardiography 27:1130–40. Reichek N, Wilson J, St John SM, et al. (1982). Noninvasive determination of left ventricular end-systolic stress: validation of the method and initial application. Circulation 65:99–108. Sahlen A, Winter R, Lind B, et al. (2008). Magnitude, reproducibility, and association with baseline cardiac function of cardiac biomarker
Biomarkers, 2014; 19(2): 114–120
release in long-distance runners aged 4 or ¼55 years. Am J Cardiol 102:218–22. Scharhag J, George K, Shave R, et al. (2008a). Exercise-associated increases in cardiac biomarkers. Med Sci Sports Exerc 40:1408–15. Scharhag J, Meyer T, Auracher M, et al. (2008b). Exercise-induced increases in NT-proBNP are not related to the exercise-induced immune response. Br J Sports Med 42:383–5. Scharhag J, Urhausen A, Schneider G, et al. (2006). Reproducibility and clinical significance of exercise-induced increases in cardiac troponins and N-terminal pro brain natriuretic peptide in endurance athletes. Eur J Cardiovasc Prev Rehabil 13:388–97. Shave R, Baggish A, George K, et al. (2010). Exercise-induced cardiac troponin elevation: evidence, mechanisms, and implications. J Am Coll Cardiol 56:169–76. Shave R, Dawson E, Whyte G, et al. (2004). Effect of prolonged exercise in a hypoxic environment on cardiac function and cardiac troponin T. Br J Sports Med 38:86–8. Shave R, George K, Whyte G, et al. (2008). Postexercise changes in left ventricular function. the evidence so far. Med Sci Sports Exerc 40: 1393–9. Silver MA, Maisel A, Yancy CW, et al. (2004). BNP Consensus Panel 2004. A clinical approach for the diagnostic, prognostic, screening, treatment monitoring, and therapeutic roles of natriuretic peptides in cardiovascular diseases. Congest Heart Fail 10:1–30. Tian Y, Nie J, Huang C, George K. (2012). The kinetics of highly sensitive cardiac troponin T release after prolonged treadmill exercise in adolescent and adult athletes. J Appl Physiol 113:418–25. Vanoverschelde JL, Younis LT, Melin JA, et al. (1991). Prolonged exercise induces left ventricular dysfunction in healthy subjects. J Appl Physiol 70:1356–63. Wu AH, Apple FS, Gibler WB, et al. (1999). National Academy of Clinical Biochemistry Standards of Laboratory Practice: recommendations for the use of cardiac markers in coronary artery diseases. Clin Chem 45:1104–21.
