Available online at www.sciencedirect.com
ScienceDirect Journal of Electrocardiology 48 (2015) 430 – 433 www.jecgonline.com
RSR′ pattern and the risk of mortality in men and women free of cardiovascular disease Wesley T. O'Neal, MD, MPH, a,⁎ Waqas Qureshi, MD, b Yabing Li, MD, c Elsayed Z. Soliman, MD, MSc, MS b, c a Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA Department of Internal Medicine, Section on Cardiology, Wake Forest School of Medicine, Winston-Salem, NC, USA Epidemiological Cardiology Research Center (EPICARE), Department of Epidemiology and Prevention, Wake Forest School of Medicine, Winston-Salem, NC, USA b
c
Abstract
This study included 6,398 participants (mean age 55 ± 0.34 years; 54% female; 49% white; 22% black; 24% Mexican; 4.3% other) free of clinical cardiovascular disease (CVD) and major ECG abnormalities. Cox regression was used to examine the association between the RSR′ (incomplete right bundle branch block (RBBB) or right ventricular conduction delay) pattern and CVD and all-cause mortalities. The RSR′ pattern was not associated with an increased risk of CVD (HR = 1.10; 95%CI = 0.63, 1.91) mortality or all-cause (HR = 0.95; 95%CI = 0.66, 1.35) mortality. The results were similar when the RSR′ pattern was further separated into incomplete RBBB and right ventricular conduction delay. In conclusion, the RSR′ pattern is a benign finding in older adults free of clinical CVD. © 2015 Elsevier Inc. All rights reserved.
Keywords:
RSR′; Mortality; Epidemiology
Introduction
Methods
The RSR′ pattern is a routinely encountered finding on the electrocardiogram (ECG). Depending on the QRS duration and whether R is taller than R′, the RSR′ pattern is part of the diagnosis of complete right bundle branch block (RBBB), incomplete RBBB, or right ventricular conduction delay according to the Minnesota Code Classification [1]. A recent report has suggested that the RSR′ pattern in the setting of QRS b 120 ms (e.g., incomplete RBBB or right ventricular conduction delay) is commonly found among healthy athletes and represents a benign finding [2]. Two reports support this hypothesis as no increased risk of adverse cardiovascular disease (CVD) events has been observed with this ECG pattern [3,4]. The prognostic significance of the RSR′ pattern in the general United States population, with males and females of diverse racial and ethnic backgrounds, has not been established. To explore the hypothesis that the RSR′ pattern is a benign condition among older adults in the general United States population, we examined the risk of mortality associated with this pattern using data from the Third National Health and Nutrition Examination Survey (NHANES III).
National Health and Nutrition Examination Survey NHANES is a periodic survey of a representative sample of the civilian non-institutionalized United States population. The purpose is to determine estimates of disease prevalence and the overall health status of the United States population. All participants gave written informed consent at the time of study enrollment. Participant characteristics, ECG methodology, and ascertainment of mortality in NHANES III have been previously published [5]. Briefly, NHANES III baseline data were collected during an in-home interview and a subsequent visit to a mobile examination center between 1988 and 1994. Data collected during the in-home interview included demographic and medication information. Blood samples were obtained at mobile centers and basic laboratory values were recorded for each participant (total cholesterol, high-density lipoprotein (HDL) cholesterol, and plasma glucose). The present analysis included 6,398 participants who were free of clinical CVD and had complete baseline demographic data, laboratory data, medication data, and mortality data available. Exclusion of participants with CVD was determined by a self-reported history of heart attack or stroke, and/or electrocardiographic evidence of myocardial infarction or major ST/T depression by Minnesota Code Classification [1].
⁎ Corresponding author at: Department of Internal Medicine, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC, USA. E-mail address: [email protected] http://dx.doi.org/10.1016/j.jelectrocard.2015.02.010 0022-0736/© 2015 Elsevier Inc. All rights reserved.
W.T. O'Neal et al. / Journal of Electrocardiology 48 (2015) 430–433
Baseline covariates Participant characteristics recorded during NHANES III were used in this analysis. Age, sex, race/ethnicity, and smoking history were self-reported. Medication history, including use of antihypertensive agents and lipid-lowering therapies also were self-reported. Smoking was defined as current or former smoker. Blood pressure measurements were obtained and values used were average readings from 3 in-home measurements and 3 mobile center measurements. Body mass index was computed as the weight in kilograms divided by the square of the height in meters. Diabetes was defined as fasting plasma glucose ≥ 126 mg/dl, glycosylated hemoglobin A1c values ≥ 6.5, or a history of diabetic medication use. RSR′ pattern Standard 12-lead ECGs were recorded using a Marquette MAC 12 system (Marquette Medical Systems, Milwaukee, WI) by trained technicians during each participants' visit to a mobile examination center. Computerized automated analysis of the ECG data was performed with visual inspection of outlier values by a trained technician in a central ECG core laboratory. The RSR′ pattern was defined according to the following Minnesota Code criteria: QRS duration of b 120 ms in each of leads I, II, III, aVL, aVF, in combination with R′ N R in lead V1 or V2 (Minnesota code 7–3 denoting incomplete RBBB); or R-R′ pattern in either of leads V1 or V2 with R′ ≤ R (Minnesota code 7–5 denoting right ventricular conduction delay). Follow-up and mortality Mortality data for NHANES III participants were available through December 31, 2006 and methods for mortality ascertainment have been described [6]. A probabilistic matching algorithm based on 12 identifiers was used to link participants with death information captured in the National Death Index. Matching identifiers included social security number, gender, and date of birth. Follow-up was defined as the interval between the NHANES III examination and either of the following, depending on whichever came first: date of death, date of censoring, or end of follow-up (December 31, 2006). The end-points of CVD and all-cause mortalities were examined and analyzed using data from the NHANES III Linked Mortality File. International Classification of Diseases, Tenth Revision codes were used to identify each endpoint. CVD mortality was defined by codes I00-I78. Participants who died of non-cardiac causes were censored at the time of death. Participants who were unable to be matched with a death record were considered to be alive through the entire follow-up period. Statistical analysis Categorical variables were reported as frequency and percentage while continuous variables were recorded as mean ± standard error. Statistical significance for categorical variables was tested using the Rao Scott chi-square statistic method and the t-test procedure for continuous variables. Unadjusted rates for CVD and all-cause
431
mortalities (per 1000 person-years) were calculated. Kaplan-Meier estimates were used to compute unadjusted survival estimates and the differences in estimates by RSR′ pattern were compared using the log-rank procedure. Cox proportional-hazards regression was used to compute hazard ratios (HR) and 95% confidence intervals (CI) for the association between the RSR′ pattern and CVD and all-cause mortalities. Multivariable models were constructed with incremental adjustments as follows: Model 1 adjusted for age, sex, and race/ethnicity; Model 2 adjusted for Model 1 covariates plus smoking status, systolic blood pressure, diabetes, body mass index, total cholesterol, HDLcholesterol, antihypertensive medication use, and lipidlowering medication use. In an additional analysis, the RSR′ pattern was further separated into incomplete RBBB (Minnesota code 7–3) and right ventricular conduction delay (Minnesota code 7–5) and the associations with CVD and all-cause mortalities were examined. A sensitivity analysis was performed with further adjustment for prolongation of the corrected QT interval (QTc) using Bazett's formula (men: ≥ 450 ms; women: ≥ 460 ms). Statistical significance was defined as p ≤ 0.05. Data were analyzed using SAS® Version 9.3 (Cary, NC USA). All analyses accounted for the complex sampling design of NHANES by including recommended sample weights.
Results A total of 6,398 study participants (mean age 55 ± 0.34 years; 54% female; 49% white; 22% black; 24% Mexican; 4.3% other) were included in this analysis. A total of 229 (3.6%) participants had an RSR′ pattern (incomplete RBBB, n = 86; right ventricular conduction delay, n = 143). The mean QRS duration for study participants was 96 ms (range 62– 119 ms) and there were no participants with QRS durations ≥ 120 ms or other ECG abnormalities. A total of 219 (3.4%) participants had QRS durations between 115 and 119 ms. Baseline characteristics stratified by the RSR′ pattern are shown in Table 1. Participants with the RSR′ pattern were older and had higher values for systolic blood pressure compared with those without the RSR′ pattern. Lower values for body mass index were observed for those with the RSR′ pattern than those without. Additionally, the QRS duration was similar between those with and without the RSR′ pattern and the number of participants with QRS values between 115 and 119 ms were similar in both groups. Over a median follow-up of 14 years (interquartile range = 12, 16), there were 786 (13%) CVD and 1977 (31%) all-cause deaths. The unadjusted Kaplan-Meier survival estimates were not significant for CVD mortality (log-rank p = 0.072; Fig. 1) but were significantly different for all-cause (log-rank p = 0.022; Fig. 2) mortality. In separate models, the RSR′ pattern was not associated with an increased risk of CVD (HR = 1.49, 95%CI = 0.88, 2.52) mortality or all-cause (HR = 1.32; 95%CI = 0.93, 1.88) mortality. Similar results were obtained with adjustment for demographics and potential confounders (Table 2). A sensitivity analysis was performed with further adjustment
432
W.T. O'Neal et al. / Journal of Electrocardiology 48 (2015) 430–433
Table 1 Baseline characteristics (N = 6398). Characteristic Age, mean (SE), years Male (%) White (%) Current or former smoker (%) Body mass index, mean (SE), kg/m2 Diabetes (%) Systolic blood pressure, mean (SE), mm Hg Total cholesterol, mean (SE), mg/dL HDL-cholesterol, mean (SE), mg/dL Antihypertensive medication use (%) Lipid-lowering medication use (%) QRS duration, ms Range Mean (SE) 115–119 ms (%) CVD mortality (%) All-cause mortality (%)
RSR′ (n = 229)
No RSR′ (n = 6,169)
p-value
58 (1.1) 120 (52) 123 (54) 143 (62) 26 (0.41) 31 (14) 130 (1.7) 215 (5.5) 51 (1.1) 38 (17) 3 (1.3)
55 (0.34) 2,854 (46) 3,035 (49) 3,331 (54) 27 (0.13) 880 (14) 127 (0.39) 217 (0.90) 51 (0.47) 1,237 (20) 186 (3.0)
b0.0001 0.10 0.10 0.21 b0.0001 0.70 0.022 0.54 0.90 0.14 0.45
70–119 99 (0.80) 13 (5.7) 36 (16) 86 (38)
62–119 96 (0.41) 206 (3.3) 750 (12) 1,891 (31)
0.88 0.16 0.14
Statistical significance tested using the t-test procedure for continuous data and the Rao-Scott chi-square test for categorical data. CVD = cardiovascular disease; HDL = high-density lipoprotein; ms = milliseconds; SE = standard error.
for prolongation of the QTc interval and the results were not materially altered (CVD mortality: HR = 1.10, 95%CI = 0.64, 1.90; all-cause mortality: HR = 0.95, 95%CI = 0.67, 1.34). The results were similar when the RSR′ pattern was further separated into incomplete RBBB (CVD mortality: HR = 1.18, 95%CI = 0.58, 2.43; all-cause mortality: HR = 0.99, 95%CI = 0.60, 1.66) and right ventricular conduction delay (CVD mortality: HR = 1.04, 95%CI = 0.44, 2.45; all-cause mortality: HR = 0.92, 95%CI = 0.56, 1.51).
In this nationally representative sample from NHANES III, the RSR′ pattern was not associated with an increased risk for CVD and all-cause mortalities among adults without clinically apparent CVD. Our findings confirm prior findings and suggest that the RSR′ pattern is a relatively benign ECG finding.
Only 2 studies have examined the prognostic significance of the RSR′ pattern. A cohort of 1,960 men aged 40 to 56 years without clinical evidence of heart disease who were followed for 20 years in the Chicago Western Electric Company study failed to show an increased risk of death due to coronary heart disease or other CVD with the presence of the RSR′ pattern [3]. Additionally, the RSR′ pattern was not associated with an increased risk of CVD and all-cause mortalities in 18,441 men and women from the Copenhagen City Heart Study [4]. Our results extend upon previous research and confirm that the RSR′ is a relatively benign finding among older adults in the general United States population and this pattern is not associated with an increased risk of CVD and all-cause mortalities. The RSR′ pattern is commonly found among young athletes in the absence of a QRS duration greater than 120 ms [2]. Although borderline left ventricular conduction delay
Fig. 1. Unadjusted Kaplan-Meier survival estimates for CVD mortality by RSR′ pattern. ⁎Kaplan-Meier estimates were not statistically different (p = 0.072).
Fig. 2. Unadjusted Kaplan-Meier survival estimates for all-cause mortality by RSR′ pattern. ⁎Kaplan-Meier estimates were statistically different (p = 0.022).
Discussion
W.T. O'Neal et al. / Journal of Electrocardiology 48 (2015) 430–433
433
Table 2 Risk of CVD and all-cause mortalities. Model 1a HR (95%CI)
p-Value
Model 2b HR (95%CI)
p-value
750/6,169 36/229
1.0 1.11 (0.68, 1.84)
– 0.67
1.0 1.10 (0.63, 1.91)
– 0.74
1,891/6,169 86/229
1.0 1.00 (0.72, 1.40)
– 0.98
1.0 0.95 (0.66, 1.35)
– 0.75
Events/no. at risk CVD mortality No RSR′ RSR′ All-cause mortality No RSR′ RSR′
CI = confidence interval; CVD = cardiovascular disease; HDL = high-density lipoprotein; HR = hazard ratio. a Adjusted for age, sex, and race/ethnicity. b Adjusted for Model 1 covariates plus systolic blood pressure, body mass index, total cholesterol, HDL-cholesterol, diabetes, smoking, antihypertensive medication use, and lipid-lowering medication use.
(QRS duration 100–119 ms) in non-hospital populations is a significant predictor of death, our results suggest that the RSR′ pattern is a benign finding in older adults [7]. Additionally, the RSR′ pattern was observed significantly more frequently in persons with low compared with high body mass index values which suggests that the RSR′ pattern is associated with a higher level of physical fitness. Furthermore, the phenomenon possibly occurs due to incorrect lead placement. It has been described that as a result of the high placement of lead V1, the RSR′ morphology occurs and likely is accompanied by an exclusively negative P wave, indicating incorrect lead placement [8]. Although we were unable to assess the accuracy of lead placement in lead V1 in our dataset, it is unlikely that incorrect lead placement completely explains this phenomenon due to the strict quality control protocols that were implemented in NHANES III. Nonetheless, whether the RSR′ pattern represents an electrical abnormality or occurs strictly due to incorrect lead placement, our results suggest that the presence of the RSR′ pattern in the ECG of an older adult without known CVD is a benign finding. Disclosures None. Acknowledgements None.
References [1] Prineas RJ, Crow RS, Blackburn HW. The Minnesota code manual of electrocardiographic findings: standards and procedures for measurement and classification. 2nd edit. London: Springer; 2010. [2] Le VV, Wheeler MT, Mandic S, et al. Addition of the electrocardiogram to the preparticipation examination of college athletes. Clin J Sport Med 2010;20:98–105. [3] Liao YL, Emidy LA, Dyer A, et al. Characteristics and prognosis of incomplete right bundle branch block: an epidemiologic study. J Am Coll Cardiol 1986;7:492–9. [4] Bussink BE, Holst AG, Jespersen L, Deckers JW, Jensen GB, Prescott E. Right bundle branch block: prevalence, risk factors, and outcome in the general population: results from the Copenhagen City Heart Study. Eur Heart J 2013;34:138–46. [5] Soliman EZ, Cammarata M, Li Y. Explaining the inconsistent associations of PR interval with mortality: the role of P-duration contribution to the length of PR interval. Heart Rhythm 2014;11:93–8. [6] Statistics NCfH. Office of Analysis and Epidemiology, The Third National Health and Nutrition Examination Survey (NHANES III) Linked Mortality File, Mortality follow-up through 2006: Matching Methodology. http://www.cdc.gov/nchs/data/datalinkage/ matching_methodology_nhanes3_final.pdf2009 [Accessed April 6th, 2014]. [7] Kurl S, Makikallio TH, Rautaharju P, Kiviniemi V, Laukkanen JA. Duration of QRS complex in resting electrocardiogram is a predictor of sudden cardiac death in men. Circulation 2012;125:2588–94. [8] Garcia-Niebla J. Comparison of p-wave patterns derived from correct and incorrect placement of V1-V2 electrodes. J Cardiovasc Nurs 2009;24:156–61.
ScienceDirect Journal of Electrocardiology 48 (2015) 430 – 433 www.jecgonline.com
RSR′ pattern and the risk of mortality in men and women free of cardiovascular disease Wesley T. O'Neal, MD, MPH, a,⁎ Waqas Qureshi, MD, b Yabing Li, MD, c Elsayed Z. Soliman, MD, MSc, MS b, c a Department of Internal Medicine, Wake Forest School of Medicine, Winston-Salem, NC, USA Department of Internal Medicine, Section on Cardiology, Wake Forest School of Medicine, Winston-Salem, NC, USA Epidemiological Cardiology Research Center (EPICARE), Department of Epidemiology and Prevention, Wake Forest School of Medicine, Winston-Salem, NC, USA b
c
Abstract
This study included 6,398 participants (mean age 55 ± 0.34 years; 54% female; 49% white; 22% black; 24% Mexican; 4.3% other) free of clinical cardiovascular disease (CVD) and major ECG abnormalities. Cox regression was used to examine the association between the RSR′ (incomplete right bundle branch block (RBBB) or right ventricular conduction delay) pattern and CVD and all-cause mortalities. The RSR′ pattern was not associated with an increased risk of CVD (HR = 1.10; 95%CI = 0.63, 1.91) mortality or all-cause (HR = 0.95; 95%CI = 0.66, 1.35) mortality. The results were similar when the RSR′ pattern was further separated into incomplete RBBB and right ventricular conduction delay. In conclusion, the RSR′ pattern is a benign finding in older adults free of clinical CVD. © 2015 Elsevier Inc. All rights reserved.
Keywords:
RSR′; Mortality; Epidemiology
Introduction
Methods
The RSR′ pattern is a routinely encountered finding on the electrocardiogram (ECG). Depending on the QRS duration and whether R is taller than R′, the RSR′ pattern is part of the diagnosis of complete right bundle branch block (RBBB), incomplete RBBB, or right ventricular conduction delay according to the Minnesota Code Classification [1]. A recent report has suggested that the RSR′ pattern in the setting of QRS b 120 ms (e.g., incomplete RBBB or right ventricular conduction delay) is commonly found among healthy athletes and represents a benign finding [2]. Two reports support this hypothesis as no increased risk of adverse cardiovascular disease (CVD) events has been observed with this ECG pattern [3,4]. The prognostic significance of the RSR′ pattern in the general United States population, with males and females of diverse racial and ethnic backgrounds, has not been established. To explore the hypothesis that the RSR′ pattern is a benign condition among older adults in the general United States population, we examined the risk of mortality associated with this pattern using data from the Third National Health and Nutrition Examination Survey (NHANES III).
National Health and Nutrition Examination Survey NHANES is a periodic survey of a representative sample of the civilian non-institutionalized United States population. The purpose is to determine estimates of disease prevalence and the overall health status of the United States population. All participants gave written informed consent at the time of study enrollment. Participant characteristics, ECG methodology, and ascertainment of mortality in NHANES III have been previously published [5]. Briefly, NHANES III baseline data were collected during an in-home interview and a subsequent visit to a mobile examination center between 1988 and 1994. Data collected during the in-home interview included demographic and medication information. Blood samples were obtained at mobile centers and basic laboratory values were recorded for each participant (total cholesterol, high-density lipoprotein (HDL) cholesterol, and plasma glucose). The present analysis included 6,398 participants who were free of clinical CVD and had complete baseline demographic data, laboratory data, medication data, and mortality data available. Exclusion of participants with CVD was determined by a self-reported history of heart attack or stroke, and/or electrocardiographic evidence of myocardial infarction or major ST/T depression by Minnesota Code Classification [1].
⁎ Corresponding author at: Department of Internal Medicine, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC, USA. E-mail address: [email protected] http://dx.doi.org/10.1016/j.jelectrocard.2015.02.010 0022-0736/© 2015 Elsevier Inc. All rights reserved.
W.T. O'Neal et al. / Journal of Electrocardiology 48 (2015) 430–433
Baseline covariates Participant characteristics recorded during NHANES III were used in this analysis. Age, sex, race/ethnicity, and smoking history were self-reported. Medication history, including use of antihypertensive agents and lipid-lowering therapies also were self-reported. Smoking was defined as current or former smoker. Blood pressure measurements were obtained and values used were average readings from 3 in-home measurements and 3 mobile center measurements. Body mass index was computed as the weight in kilograms divided by the square of the height in meters. Diabetes was defined as fasting plasma glucose ≥ 126 mg/dl, glycosylated hemoglobin A1c values ≥ 6.5, or a history of diabetic medication use. RSR′ pattern Standard 12-lead ECGs were recorded using a Marquette MAC 12 system (Marquette Medical Systems, Milwaukee, WI) by trained technicians during each participants' visit to a mobile examination center. Computerized automated analysis of the ECG data was performed with visual inspection of outlier values by a trained technician in a central ECG core laboratory. The RSR′ pattern was defined according to the following Minnesota Code criteria: QRS duration of b 120 ms in each of leads I, II, III, aVL, aVF, in combination with R′ N R in lead V1 or V2 (Minnesota code 7–3 denoting incomplete RBBB); or R-R′ pattern in either of leads V1 or V2 with R′ ≤ R (Minnesota code 7–5 denoting right ventricular conduction delay). Follow-up and mortality Mortality data for NHANES III participants were available through December 31, 2006 and methods for mortality ascertainment have been described [6]. A probabilistic matching algorithm based on 12 identifiers was used to link participants with death information captured in the National Death Index. Matching identifiers included social security number, gender, and date of birth. Follow-up was defined as the interval between the NHANES III examination and either of the following, depending on whichever came first: date of death, date of censoring, or end of follow-up (December 31, 2006). The end-points of CVD and all-cause mortalities were examined and analyzed using data from the NHANES III Linked Mortality File. International Classification of Diseases, Tenth Revision codes were used to identify each endpoint. CVD mortality was defined by codes I00-I78. Participants who died of non-cardiac causes were censored at the time of death. Participants who were unable to be matched with a death record were considered to be alive through the entire follow-up period. Statistical analysis Categorical variables were reported as frequency and percentage while continuous variables were recorded as mean ± standard error. Statistical significance for categorical variables was tested using the Rao Scott chi-square statistic method and the t-test procedure for continuous variables. Unadjusted rates for CVD and all-cause
431
mortalities (per 1000 person-years) were calculated. Kaplan-Meier estimates were used to compute unadjusted survival estimates and the differences in estimates by RSR′ pattern were compared using the log-rank procedure. Cox proportional-hazards regression was used to compute hazard ratios (HR) and 95% confidence intervals (CI) for the association between the RSR′ pattern and CVD and all-cause mortalities. Multivariable models were constructed with incremental adjustments as follows: Model 1 adjusted for age, sex, and race/ethnicity; Model 2 adjusted for Model 1 covariates plus smoking status, systolic blood pressure, diabetes, body mass index, total cholesterol, HDLcholesterol, antihypertensive medication use, and lipidlowering medication use. In an additional analysis, the RSR′ pattern was further separated into incomplete RBBB (Minnesota code 7–3) and right ventricular conduction delay (Minnesota code 7–5) and the associations with CVD and all-cause mortalities were examined. A sensitivity analysis was performed with further adjustment for prolongation of the corrected QT interval (QTc) using Bazett's formula (men: ≥ 450 ms; women: ≥ 460 ms). Statistical significance was defined as p ≤ 0.05. Data were analyzed using SAS® Version 9.3 (Cary, NC USA). All analyses accounted for the complex sampling design of NHANES by including recommended sample weights.
Results A total of 6,398 study participants (mean age 55 ± 0.34 years; 54% female; 49% white; 22% black; 24% Mexican; 4.3% other) were included in this analysis. A total of 229 (3.6%) participants had an RSR′ pattern (incomplete RBBB, n = 86; right ventricular conduction delay, n = 143). The mean QRS duration for study participants was 96 ms (range 62– 119 ms) and there were no participants with QRS durations ≥ 120 ms or other ECG abnormalities. A total of 219 (3.4%) participants had QRS durations between 115 and 119 ms. Baseline characteristics stratified by the RSR′ pattern are shown in Table 1. Participants with the RSR′ pattern were older and had higher values for systolic blood pressure compared with those without the RSR′ pattern. Lower values for body mass index were observed for those with the RSR′ pattern than those without. Additionally, the QRS duration was similar between those with and without the RSR′ pattern and the number of participants with QRS values between 115 and 119 ms were similar in both groups. Over a median follow-up of 14 years (interquartile range = 12, 16), there were 786 (13%) CVD and 1977 (31%) all-cause deaths. The unadjusted Kaplan-Meier survival estimates were not significant for CVD mortality (log-rank p = 0.072; Fig. 1) but were significantly different for all-cause (log-rank p = 0.022; Fig. 2) mortality. In separate models, the RSR′ pattern was not associated with an increased risk of CVD (HR = 1.49, 95%CI = 0.88, 2.52) mortality or all-cause (HR = 1.32; 95%CI = 0.93, 1.88) mortality. Similar results were obtained with adjustment for demographics and potential confounders (Table 2). A sensitivity analysis was performed with further adjustment
432
W.T. O'Neal et al. / Journal of Electrocardiology 48 (2015) 430–433
Table 1 Baseline characteristics (N = 6398). Characteristic Age, mean (SE), years Male (%) White (%) Current or former smoker (%) Body mass index, mean (SE), kg/m2 Diabetes (%) Systolic blood pressure, mean (SE), mm Hg Total cholesterol, mean (SE), mg/dL HDL-cholesterol, mean (SE), mg/dL Antihypertensive medication use (%) Lipid-lowering medication use (%) QRS duration, ms Range Mean (SE) 115–119 ms (%) CVD mortality (%) All-cause mortality (%)
RSR′ (n = 229)
No RSR′ (n = 6,169)
p-value
58 (1.1) 120 (52) 123 (54) 143 (62) 26 (0.41) 31 (14) 130 (1.7) 215 (5.5) 51 (1.1) 38 (17) 3 (1.3)
55 (0.34) 2,854 (46) 3,035 (49) 3,331 (54) 27 (0.13) 880 (14) 127 (0.39) 217 (0.90) 51 (0.47) 1,237 (20) 186 (3.0)
b0.0001 0.10 0.10 0.21 b0.0001 0.70 0.022 0.54 0.90 0.14 0.45
70–119 99 (0.80) 13 (5.7) 36 (16) 86 (38)
62–119 96 (0.41) 206 (3.3) 750 (12) 1,891 (31)
0.88 0.16 0.14
Statistical significance tested using the t-test procedure for continuous data and the Rao-Scott chi-square test for categorical data. CVD = cardiovascular disease; HDL = high-density lipoprotein; ms = milliseconds; SE = standard error.
for prolongation of the QTc interval and the results were not materially altered (CVD mortality: HR = 1.10, 95%CI = 0.64, 1.90; all-cause mortality: HR = 0.95, 95%CI = 0.67, 1.34). The results were similar when the RSR′ pattern was further separated into incomplete RBBB (CVD mortality: HR = 1.18, 95%CI = 0.58, 2.43; all-cause mortality: HR = 0.99, 95%CI = 0.60, 1.66) and right ventricular conduction delay (CVD mortality: HR = 1.04, 95%CI = 0.44, 2.45; all-cause mortality: HR = 0.92, 95%CI = 0.56, 1.51).
In this nationally representative sample from NHANES III, the RSR′ pattern was not associated with an increased risk for CVD and all-cause mortalities among adults without clinically apparent CVD. Our findings confirm prior findings and suggest that the RSR′ pattern is a relatively benign ECG finding.
Only 2 studies have examined the prognostic significance of the RSR′ pattern. A cohort of 1,960 men aged 40 to 56 years without clinical evidence of heart disease who were followed for 20 years in the Chicago Western Electric Company study failed to show an increased risk of death due to coronary heart disease or other CVD with the presence of the RSR′ pattern [3]. Additionally, the RSR′ pattern was not associated with an increased risk of CVD and all-cause mortalities in 18,441 men and women from the Copenhagen City Heart Study [4]. Our results extend upon previous research and confirm that the RSR′ is a relatively benign finding among older adults in the general United States population and this pattern is not associated with an increased risk of CVD and all-cause mortalities. The RSR′ pattern is commonly found among young athletes in the absence of a QRS duration greater than 120 ms [2]. Although borderline left ventricular conduction delay
Fig. 1. Unadjusted Kaplan-Meier survival estimates for CVD mortality by RSR′ pattern. ⁎Kaplan-Meier estimates were not statistically different (p = 0.072).
Fig. 2. Unadjusted Kaplan-Meier survival estimates for all-cause mortality by RSR′ pattern. ⁎Kaplan-Meier estimates were statistically different (p = 0.022).
Discussion
W.T. O'Neal et al. / Journal of Electrocardiology 48 (2015) 430–433
433
Table 2 Risk of CVD and all-cause mortalities. Model 1a HR (95%CI)
p-Value
Model 2b HR (95%CI)
p-value
750/6,169 36/229
1.0 1.11 (0.68, 1.84)
– 0.67
1.0 1.10 (0.63, 1.91)
– 0.74
1,891/6,169 86/229
1.0 1.00 (0.72, 1.40)
– 0.98
1.0 0.95 (0.66, 1.35)
– 0.75
Events/no. at risk CVD mortality No RSR′ RSR′ All-cause mortality No RSR′ RSR′
CI = confidence interval; CVD = cardiovascular disease; HDL = high-density lipoprotein; HR = hazard ratio. a Adjusted for age, sex, and race/ethnicity. b Adjusted for Model 1 covariates plus systolic blood pressure, body mass index, total cholesterol, HDL-cholesterol, diabetes, smoking, antihypertensive medication use, and lipid-lowering medication use.
(QRS duration 100–119 ms) in non-hospital populations is a significant predictor of death, our results suggest that the RSR′ pattern is a benign finding in older adults [7]. Additionally, the RSR′ pattern was observed significantly more frequently in persons with low compared with high body mass index values which suggests that the RSR′ pattern is associated with a higher level of physical fitness. Furthermore, the phenomenon possibly occurs due to incorrect lead placement. It has been described that as a result of the high placement of lead V1, the RSR′ morphology occurs and likely is accompanied by an exclusively negative P wave, indicating incorrect lead placement [8]. Although we were unable to assess the accuracy of lead placement in lead V1 in our dataset, it is unlikely that incorrect lead placement completely explains this phenomenon due to the strict quality control protocols that were implemented in NHANES III. Nonetheless, whether the RSR′ pattern represents an electrical abnormality or occurs strictly due to incorrect lead placement, our results suggest that the presence of the RSR′ pattern in the ECG of an older adult without known CVD is a benign finding. Disclosures None. Acknowledgements None.
References [1] Prineas RJ, Crow RS, Blackburn HW. The Minnesota code manual of electrocardiographic findings: standards and procedures for measurement and classification. 2nd edit. London: Springer; 2010. [2] Le VV, Wheeler MT, Mandic S, et al. Addition of the electrocardiogram to the preparticipation examination of college athletes. Clin J Sport Med 2010;20:98–105. [3] Liao YL, Emidy LA, Dyer A, et al. Characteristics and prognosis of incomplete right bundle branch block: an epidemiologic study. J Am Coll Cardiol 1986;7:492–9. [4] Bussink BE, Holst AG, Jespersen L, Deckers JW, Jensen GB, Prescott E. Right bundle branch block: prevalence, risk factors, and outcome in the general population: results from the Copenhagen City Heart Study. Eur Heart J 2013;34:138–46. [5] Soliman EZ, Cammarata M, Li Y. Explaining the inconsistent associations of PR interval with mortality: the role of P-duration contribution to the length of PR interval. Heart Rhythm 2014;11:93–8. [6] Statistics NCfH. Office of Analysis and Epidemiology, The Third National Health and Nutrition Examination Survey (NHANES III) Linked Mortality File, Mortality follow-up through 2006: Matching Methodology. http://www.cdc.gov/nchs/data/datalinkage/ matching_methodology_nhanes3_final.pdf2009 [Accessed April 6th, 2014]. [7] Kurl S, Makikallio TH, Rautaharju P, Kiviniemi V, Laukkanen JA. Duration of QRS complex in resting electrocardiogram is a predictor of sudden cardiac death in men. Circulation 2012;125:2588–94. [8] Garcia-Niebla J. Comparison of p-wave patterns derived from correct and incorrect placement of V1-V2 electrodes. J Cardiovasc Nurs 2009;24:156–61.
