International Journal of Cardiology 170 (2014) 358–363
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Muscle function in adults with congenital heart disease☆ Linda Ashman Kröönström a,d,⁎, Linda Johansson a, Anna-Klara Zetterström a, Mikael Dellborg b,c, Peter Eriksson b,c, Åsa Cider a,d a
Physical therapy department, Sahlgrenska University Hospital, University of Gothenburg, Gothenburg, Sweden ACHD Unit, Sahlgrenska University Hospital, University of Gothenburg, Gothenburg, Sweden Institute of Medicine, University of Gothenburg, Gothenburg, Sweden d Institute of Neuroscience and Physiology/Physiotherapy, University of Gothenburg, Gothenburg, Sweden b c
a r t i c l e
i n f o
Article history: Received 27 June 2013 Received in revised form 18 October 2013 Accepted 2 November 2013 Available online 13 November 2013 Keywords: Muscle function ACHD Muscle strength Muscle strength dynamometer NYHA
a b s t r a c t Background: The aim was to assess muscle function in a sample of Swedish adult men and women with congenital heart disease (ACHD) and to compare the results with published reference values in healthy adults. Methods and results: From April 2009 to December 2010, 762 adult outpatients were assessed for their suitability and individual need for tests of physical fitness. The patients performed five muscle function tests, two isotonic tests and three isometric tests. Of the 762 patients, 315 (41.3%) patients performed the tests. Patients with ACHD had lower isotonic muscle function compared to healthy reference values. In the heel lift test, men with ACHD performed at 63% and women at 58% of the healthy reference values and in the shoulder flexion test the corresponding performance level was 60% for men with ACHD and 85% for the women. Multiple regression analyses showed that NYHA class II–IV was a significant predictor for a lower isotonic muscle function i.e. heel lift in women (p b 0.001) and men (p = 0.05) and in shoulder flexion (p b 0.001) in women, as well as in isometric knee extension (p = 0.04) and isometric shoulder abduction (p b 0.001) in women. Conclusion: This is the first report of muscle function in a broad and unselected group of patients with ACHD. Our data shows that patients with ACHD have lower isotonic muscle function. The impacts of low muscle function in activities of daily living and the question of whether muscle function could be improved with exercise training need further investigation. © 2013 Elsevier Ireland Ltd. All rights reserved.
1. Introduction Due to improvements in care, an increasing number of adults with congenital heart disease (ACHD) reach adulthood [1]. ACHD is one of the most common malformations with an incidence of slightly less than 1% of live births. The variation in clinical presentation is large, some malformations presenting themselves within a few hours or days after birth, others later in life [2]. In Sweden there are approximately 25,000–30,000 patients with ACHD, all degrees of severity included, and as in many other countries, the population of patients with ACHD is now most likely larger than the population of children with CHD [3]. In general, physical activity is recommended for most, if not all, patients with acquired heart disease, as well as for primary prevention. On a similar note, the European Society of Cardiology states that regular exercise at recommended levels can be performed and should be
☆ The authors take responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation. ⁎ Corresponding author at: Physical therapy department, Sahlgrenska University Hospital, University of Gothenburg, Gothenburg, Sweden. Tel.: + 46 31 3434463; fax: + 46 31 3434469. E-mail address: [email protected] (L.A. Kröönström). 0167-5273/$ – see front matter © 2013 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijcard.2013.11.014
encouraged in all patients with ACHD [4]. Several studies have shown that these patients have a lower aerobic capacity, than healthy individuals [5–7]. However, the precise reasons for this are not clear. The lower aerobic exercise capacity could be caused by the congenital lesion per se or by the postoperative anatomical- and physiological conditions, for example reduced ventricular function, or reduced preload due to increased pulmonary vascular resistance [7]. Anxiety and fear of being physically active could also be contributory factors. Overprotection not only from parents, school, and friends but also from physicians and nurses is probably quite common [8]. This will lead not only to reduced exercise capacity but also to lower levels of physical activity, as compared to healthy individuals [9]. A low level of physical activity is a risk factor for developing other health problems [8] such as diabetes, obesity and acquired cardiovascular diseases [10]. Regular physical activity, on the other hand, is associated with a range of health benefits such as improved mental health, decreased rate of anxiety and depression, and improved self-esteem [9]. Apart from the underlying heart malformation, a lower level of physical activity and a non-exercising lifestyle per se can reduce aerobic exercise capacity. In other populations, low aerobic exercise capacity has been shown to be associated with poor muscle function. Although levels of physical activity and aerobic exercise capacity have been studied in patients with ACHD, little is known about these patients' muscle
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function. A lower maximal hand grip has been reported [11,12], while others have found a normal muscle and bone development (in proportion to the patient's height) in adolescents and young adults with congenital heart disease [13]. We observed in some patients what seemed to be a relationship between poor muscle function and symptoms such as pain and weakness and therefore decided to assess muscle function. The overall aim of the study was thus to assess muscle function in a sample of Swedish adult men and women with ACHD and to compare the results with published reference values in healthy adults.
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2.4.3.1. Reference group. The results of the patients with ACHD were compared to reference values in the Jamar — Hydraulic Hand dynamometer owner's manual [17]. Reference values were available for ages 6–75 years. Inter- and intra-rater reliability is good for this instrument [18].
2.4.4. Unilateral isometric knee extension Knee extension was assessed with IsoForce Control® (Medical Device Solutions, Oberburg, Switzerland), which is a portable isometric dynamometer measuring static muscle strength. The patient sat on a stool, back touching the wall, with the testing leg in 90° knee flexion, with a strap around the dominant leg just over the malleolus. The other leg was stretched forward with the heel touching the floor.
2. Patients and methods The adult congenital heart unit (ACHD unit) at Sahlgrenska University Hospital/Östra serves a population of 1.5 million and is the only complete unit within that area. Adult patients with known ACHD are seen at that unit and children within the catchment area are referred to the unit when they reach 18 years of age. 2.1. Study population From April 2009 to December 2010, all outpatients with ACHD seen at regular visits in our ACHD unit were assessed for potential contraindications and, if none were present, the patient was referred to see a specially trained physiotherapist connected to the ACHD unit. 2.2. Exclusion criteria The exclusion criteria were severe arrhythmias, patients due to undergo surgery, advanced heart failure, severe cerebral lesions, or intellectual disabilities that made it difficult to perform the muscle function tests. Patients were given verbal and written information about the study and signed a letter of informed consent. The study was approved by the local ethics committee and followed the ethical guidelines of the 1975 Declaration of Helsinki [14]. 2.3. Reference group A description of the reference values used to compare with the results of patients with ACHD will be presented after the description of each muscle function test. 2.4. Measurements Measurements were chosen to evaluate muscle function in upper and lower extremities as well as isotonic and isometric muscle functions. The patients performed five muscle function tests, two isotonic and three isometric tests, in the following order: isotonic shoulder flexion, isometric handgrip strength, isotonic heel lift, isometric shoulder abduction, and isometric knee extension. All three isometric tests were performed three times with approximately 30 seconds' rest between trials. Standardized instructions were given by the physiotherapists leading the test. No verbal encouragement was used during the tests but instructions to undertake all of the tests with maximum effort were given in advance. 2.4.1. Unilateral isotonic shoulder flexion The patient sat on a stool, back touching the wall, and held a weight in the hand of the arm to be tested (3 kg for men and 2 kg for women). The patient was asked to elevate the testing arm, from 0 to 90° flexion, as many times as possible at the speed of 20 contractions per minute using a metronome (Wittner Taktell Piccolo, Germany).
2.4.4.1. Reference group. No reference values were available. The reliability of this test has not been evaluated.
2.4.5. Unilateral isometric shoulder abduction Shoulder abduction was assessed with IsoForce Control® (Medical Device Solutions, Oberburg, Switzerland), which is a portable isometric dynamometer measuring static muscle strength. The patient sat on a stool, back touching the wall, legs stretched forward and crossed with one heel touching the floor. The patient's arm was elevated to 90° in the scapula direction and a strap was placed around the wrist (styloid process) on the dominant arm.
2.4.5.1. Reference group. The results of the patients with ACHD were compared to healthy reference values of 19–57 year olds [19]. IsoForce has been tested for intra-rater and inter-rater reliability [20].
2.5. Statistical methods Data were analyzed using Statistical Package for Social Sciences (SPSS) 17.0 for Windows (Chicago, Illinois, USA). Demographic data are presented as mean value and one standard deviation (SD). The Independent-samples T-test was used for comparison of muscle function between patients with ACHD and reference values. Muscle function is presented as percent of reference values. Age-adjusted reference values were used for two of the isometric tests [17,19]. Diagnosis groups were formed based on the categories used by the Swedish national adult congenital heart registry. To form larger groups, these categories were combined into the following three groups: Less complicated, Corrected and Complex diagnosis. Less complicated diagnosis consisted of simple shunts, aortic valve malformations, aortic anomalies, mitral valve lesions, pulmonary valve lesions and tricuspidalis valve lesions. Corrected diagnosis consisted of right ventricular/tetralogy of Fallot and transposition of the great arteries. Complex diagnosis consisted of truncus arteriosus, univentricular repair and others. This arbitrary division was made to investigate whether differences in muscle function could be related to degree and severity of malformations and to facilitate statistical analysis. The type of multiple regression used was Enter and was used to assess the association between muscle function, sex, age, the functional classification system of the New York heart Association (NYHA) [21] and different diagnosis groups. NYHA was dichotomized into two groups, NYHA I and NYHA II–IV. Tests were two-sided and the pvalue was set to b 0.05.
3. Results 3.1. Recruitment and demographics
2.4.1.1. Reference group. The results of the patients with ACHD were compared to healthy men and women aged 60 or above. This test shows good test–retest reliability [15]. 2.4.2. Unilateral isotonic heel lift Heel lifts are performed on a 10° wedge, one lift every other second using a metronome (Wittner Taktell Piccolo, Germany). Patients were allowed to touch the wall for balance and on each rise the head had to touch a marker on a measuring stick that was calibrated in advance. The contralateral foot was held slightly above the floor. The test was terminated if the knee on the tested leg was bent or if it was impossible for the patient to follow the pace. The number of maximal heel lifts was registered for each leg. 2.4.2.1. Reference group. The results of the patients with ACHD were compared to an urban population sample of men and women aged from 40 to 79 years [16]. This test has good test–retest reliability [15]. 2.4.3. Isometric handgrip strength Handgrip strength was measured with Jamar® (Sammons Preston Rolyan, Chicago, USA), which is a hydraulic dynamometer measuring maximum handgrip strength in the cylindrical grip. The patient was seated on a chair without armrests, shoulder adducted, and the elbow of the hand tested was held at 90°.
Seven hundred and sixty-two outpatients seen at a specialized ACHD unit were assessed and screened for their suitability and individual need for tests of physical function. The demographics of this population are given in Table 1. Three hundred and fifteen (41.3%) patients performed the tests. Four hundred forty seven (58.7%) patients did not perform the tests for one of the following reasons: declined to participate, psychiatric disorders, unstable or severe cardiac condition, musculoskeletal disorders, intellectual or cerebral disability, pregnancy, discontinuation of planned care (i.e. moving outside the catchment area) or other or unknown reasons. A flowchart of the patient recruitment is presented in Fig. 1. Of the 315 (41.3%) patients, 161 were men (51.1%) and 154 were women (48.9%), see Table 2. Age ranged from 18 to 75 years and the mean age was 34 years. The NYHA class of all patients was determined. No significant differences were seen in patients who performed the tests, in comparison to patients who declined to participate or who for other reasons did not perform the tests, see Table 1.
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Table 1 Descriptive data of all patients, n = 762.
Age, in years: mean (SD) Men n (%) Women n (%) Diagnosis group: Less complicated n (%) Corrected n (%) Complex n (%) NYHA class: I/II/III/IV n (%)
Table 2 Descriptive data of included patients, n = 315.
Included patients
Not included patients
p-Value Sex difference
34 (13) 161 (51%) 154 (49%)
36 (15) 226 (50.6%) 221 (49.4%)
ns ns
234 (74.3%) 67 (21.3%) 14 (4.4%) 256 (81.5%) 47 (15%) 11 (3.5%) 0
354 (79.2%) 76 (17%) 17 (3.8%) 341 (78.4%) 74 (17%) 17 (3.9%) 3 (0.7%)
ns
ns
Less complicated diagnosis consisted of simple shunts, aortic valve malformations, aortic anomalies, mitral valve lesions, pulmonary valve lesions and tricuspidalis valve lesions. Corrected diagnosis consisted of right ventricular/tetralogy of Fallot and transposition of the great arteries. Complex diagnosis consisted of truncus arteriosus, univentricular repair and others.
3.2. Muscle function, comparison of groups based on functional classification (NYHA) and diagnostic group Results of the isometric muscle function tests are presented in Table 3 and results of the isotonic muscle function tests are presented in Figs. 2 and 3. While isometric muscle function appeared to be similar to reference values, isotonic muscle function in both the upper and lower parts of the body was poorer (Figs. 2 and 3). In
Age, in years, mean (SD) Diagnosis group: Less complicated n (%) Corrected n (%) Complex n (%) NYHA I n (%) NYHA II n (%) NYHA III n (%) NYHA IV n (%) Reconstructive cardiac surgery n (%) Smokers n (%) Medication n (%) Beta-blockers n (%) ACE inhibitors n (%) Warfarin n (%) Aspirin n (%) Diuretics n (%) Angiotensin 2 blockers n (%) Aldosterone inhibitors n (%) Digitalis n (%) Other n (%)
Men, n = 161
Women, n = 154
p-Value
33 (12)
36 (14)
0.022
115 (71.4%) 40 (24.8%) 6 (3.7%) 142 (88.2%) 15 (9.3%) 4 (2.5%) 0 134 (84.8%) 14 (9%) 76 (49.4%) 42 (29.2%) 22 (15.3%) 22 (15.3%) 12 (8.3%) 10 (6.9%) 4 (2.8%) 0 (0%) 3 (2.1%) 4 (3.3%)
119 (77.3%) 27 (17.5%) 8 (5.2%) 114 (74.5%) 32 (20.9%) 7 (4.6%) 0 113 (74.8%) 14 (9.3%) 71 (47.7%) 31 (22%) 14 (9.9%) 17 (12.1%) 22 (15.6%) 10 (7.1%) 2 (1.4%) 0 (0%) 3 (2.2%) 6 (5.2%)
0.256
0.007
0.029 0.913 0.767 0.165 0.174 0.429 0.058 0.961 0.424 0.993 0.474
Less complicated diagnosis consisted of simple shunts, aortic valve malformations, aortic anomalies, mitral valve lesions, pulmonary valve lesions and tricuspidalis valve lesions. Corrected diagnosis consisted of right ventricular/tetralogy of Fallot and transposition of the great arteries. Complex diagnosis consisted of truncus arteriosus, univentricular repair and others.
the heel lift test, men with ACHD performed at 63% and women performed at 58% of the healthy reference values. In the shoulder flexion test, men with ACHD performed at 60% and the women at 85% of the healthy reference values. The multiple regression analyses showed that age has a significant negative impact on muscle function in knee extension in women (p = 0.01), and shoulder abduction (p = 0.05) and the heel lift in men (p b 0.001), see Table 4. Higher NYHA class II–IV was a significant predictor for a decrease in isotonic muscle function, i.e. heel lift in women (p b 0.001) and men (p = 0.05) and shoulder flexion (p b 0.001) in women. Furthermore, NYHA class II–IV significantly predicted lower isometric knee extension (p = 0.04) and isometric shoulder abduction (p b 0.001) in women. No other significant results were seen when comparing muscle function in relation to NYHA class. There were no significant differences in muscle function for the three diagnosis groups. 4. Discussion
Fig. 1. Patient recruitment.
This study shows that patients with ACHD have significantly reduced isotonic muscle function compared to healthy reference values. Our results also show lower muscle function, in several muscle groups, in relation to severity of NYHA class. Though NYHA classification is widely used within research in cardiology, its validity, reliability and sensitivity are less well documented in the current setting [22]. There are reports indicating a “difference in patients' self-assessed functional classification compared to investigators' reported NYHA classification” [23] and Gratz et al. have stressed the importance of testing all patients' level of physical fitness [24], as patients with ACHD may underestimate their symptoms due to “never having experienced unimpaired physical exertion as their healthy counterparts have”. Furthermore, patients with ACHD may have made lifelong psychosocial adaptations on the basis of their congenital defects, and may thus consider their situation to be normal [24]. This study found no relation between diagnosis groups and muscle function. Our results show a lower muscle function, in a few muscle groups as a function of age, which is coherent with the results of other
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Table 3 Isometric muscle function test in patients with congenital heart disease. Variable
All patients
Shoulder abduction, kg, mean (SD) Knee extension, kg, mean (SD) Handgrip, kg, mean (SD)
6.9 (2.8) n = 290 23.5 (7.7) n = 286 37.2 (16.8) n = 221
a
% of reference value a n.a
Men
% of reference valuea
Women
% of reference valuea
p-Value Sex difference
8.7 (2.6) n = 147 26.4 (7.2) n = 143 46 (16) n = 114
96% n.a 90%
5.1 (1.6) n = 143 20.6 (7.2) n = 143 27.9 (11.9) n = 107
109% n.a 87%
b0.001 b0.001 b0.001
Percent of age-adjusted reference value. n.a = not available.
authors [16]. Furthermore, men had better muscle strength than women, which is also in accordance with the results of other authors [16,25]. Lower muscle function has been found in several other diagnoses such as chronic obstructive pulmonary disease [26] and chronic heart failure (CHF) [27]. Skeletal muscle weakness has also been seen in other congenital diseases such as cystic fibrosis [28]. As muscle function is lower in the above mentioned congenital diseases, it may be surmised that a physically inactive lifestyle contributes to the lower muscle function. For example, in patients with the Fontan procedure, physical activity is primarily associated with factors unrelated to cardiac status [29]. Even though muscle function has been studied for many other diagnoses, it has scarcely been assessed in patients with ACHD. The isotonic muscle function tests used in this study were developed as a method to test muscles and muscle function used in activities of daily living [15]. Patients with CHF have also been found to have significantly lower isotonic endurance in shoulder flexion and heel lift [15]. It is well known that one of the major symptoms in patients with CHF is decreased muscle function [27]. Studies of patients with CHF show decreased muscle function in isotonic muscular endurance, possibly due to maladaptation in skeletal muscle fibers
together with low levels of physical activity [15]. An important contributing factor to impaired physical fitness is an inactive lifestyle, as often observed in patients with ACHD. It has been claimed that this could be the result of overprotection by parental or environmental overprotection [8]. One article showed that adequate discussions with the patient of the importance of fitness and the prescription of an individually tailored exercise program were rare. In 71% of cases, the topic of exercise had not been spontaneously raised by the pediatrician, the general practitioner, or the cardiologist at the adult clinic [30]. In Sweden (at the above-mentioned ACHD unit) patients with ACHD have not routinely been given the opportunity to seek treatment from a physiotherapist, yet the advantages of physiotherapy connected with an ACHD-unit are many. Given the wide variety of diagnosis with different degrees of severity, the changes in symptoms over time and the fact that patients with ACHD often require lifelong follow-up, both patients and medical staff benefit from a close cooperation. During this study no heart-related incidents or incidents concerning musculoskeletal problems occurred. The prevalence of incidents during tests of physical fitness for patients with ACHD is unknown. Cumulative medical experience has shown that patients with ACHD have a very low risk of incidents
Fig. 2. Isotonic muscle function test: heel lift test in patients with ACHD compared to healthy reference values.
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Fig. 3. Isotonic muscle function test: shoulder flexion test in patients with ACHD compared to healthy reference values.
during exercise [8]. Despite this, it is necessary to have access to equipment and training for cardiac and pulmonary resuscitation (CPR) when testing patients with ACHD [31]. The relationship between muscle function, congenital heart disease and level of physical activity is not clear. Whether the lower muscle function is due to physical inactivity or maladaptation in skeletal muscle fibers, is yet to be discovered. No exercise studies have been found that investigate training of muscle function. The mean age of the patients in this study was 34 years. Considering that muscle function is significantly lower at this age compared to healthy individuals, one will have to take into consideration the consequences if the patient's muscle function continues to decrease. Further studies in patients with ACHD should focus on whether muscle function can increase with training. One possibility is to prescribe individually tailored exercise programs to maintain or increase muscle function for patients with ACHD as part of their regular visits to the ACHD unit.
lack of tests of reliability data regarding this test. One other limitation of this study was that there was not one single group of reference values with which it was possible to compare all tests of muscle functions with. A group of healthy individuals who had all performed the same tests would have been preferred. In this study, tests of muscle function were compared to various available reference values [15–17,19]. Reference values for the isotonic muscle function tests were obtained for controls substantially older than the present patient population and the difference between patients and controls may therefore have been underestimated. The patients who declined to participate did not differ from the participants concerning age, NYHA class or diagnosis group. However, the level of physical activity is not known and therefore one cannot know if these patients choose not to participate because of high or low levels of physical activity and training, nor whether they had a similar activity level to the participants.
4.1. Limitations of the present study 5. Conclusions There are certain problems in trying to assess a person's muscle function: firstly, there is unfamiliarity among patients with the form of muscle function tests; secondly, there is the problem of patient motivation, as some patients will push themselves closer to their maximum working capacity than others [32]. One aspect to take into consideration is the familiarization effect. The three tests of isometric strength were all carried out three times each and a mean value was calculated, which would minimize the risk of the familiarization effect and therefore gave a more valid result. The verbal communication between the patient and the investigator is also important. Therefore, verbal communication was standardized and no encouragement was given during the tests. In this group of patients, including some cases of mental retardation, such as in patients with Down's syndrome [33], it is especially important to ensure that the instructions are as clear as possible. One limitation of the study is the lack of reference values for the knee extension test, as well as
Our data shows that patients with ACHD have a lower isotonic muscle function compared to reference values. The impact of the lower muscle function in activities of daily living and the question of whether muscle function could be improved with exercise training need further investigation.
Acknowledgments The authors wish to thank Georgios Lappas for help with statistical advice and the Research and Development of Region Västra Götaland, the Heart and Lung Foundation and ALF-LUA funds for economic support. The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology.
L.A. Kröönström et al. / International Journal of Cardiology 170 (2014) 358–363 Table 4 Age, NYHA, diagnosis groups and sex and their influence on the five different muscle function tests. Sex
Test of muscle function
Variable
Estimate
Lower limit
Upper limit
p-Value
M
Knee extension
Age Corrected Complex NYHA II/II/IV Age Corrected Complex NYHA II/II/IV Age Corrected Complex NYHA II/II/IV Age Corrected Complex NYHA II/II/IV Age Corrected Complex NYHA II/II/IV Age Corrected Complex NYHA II/II/IV Age Corrected Complex NYHA II/II/IV Age Corrected Complex NYHA II/II/IV Age Corrected Complex NYHA II/II/IV Age Corrected Complex NYHA II/II/IV
−0.04 −1.13 3.43 0.40 −0.11 0.98 −2.72 −3.11 −0.04 −0.93 0.44 0.03 −0.02 −0.34 0.17 −1.21 0.12 −4.48 3.06 −6.14 0.06 −4.37 −4.36 −4.32 −0–20 −3.00 −3.17 −5.10 −0.04 −0.18 1.26 −7.81 0.04 −4.06 −6.56 −9.45 0.16 −1.60 −2.42 −22.92
−0.14 −3.99 −2.66 −3.58 −0.20 −2.10 −8.41 −6.12 −0.07 −1.93 −1.72 −1.43 −0.04 −1.03 −1.10 −1.88 −0.15 −11.94 −13.29 −16.82 −0.12 −10.32 −15.33 −10.65 −0.32 −6.58 −11.00 −10.21 −0.16 −3.97 −5.89 −11.63 −0.21 −11.33 −22.67 −19.65 −0.27 −16.43 −30.60 −37.30
0.06 1.72 9.52 4.38 −0.02 4.06 2.98 −0.10 0.00 0.07 2.61 1.49 0.00 0.35 1.44 −0.54 0.38 2.98 19.41 4.54 0.25 1.58 6.62 2.02 −0.07 0.59 4.67 0.00 0.07 3.60 8.41 −3.99 0.30 3.21 9.54 0.75 0.59 13.23 25.76 −8.53
0.42 0.43 0.27 0.84 0.01 0.53 0.35 0.04 0.05 0.07 0.69 0.97 0.09 0.33 0.79 0.00 0.38 0.24 0.71 0.26 0.51 0.15 0.43 0.18 0.00 0.10 0.43 0.05 0.46 0.92 0.73 0.00 0.75 0.27 0.42 0.07 0.46 0.83 0.87 0.00
F
M
Shoulder abduction
F
M
Handgrip
F
M
Heel-lift, right
F
M
Shoulder flexion
F
M = male, F = female, Diagnosis group: Less complicated/Corrected/Complex.
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[7] Kempny A, Dimopoulos K, Uebing A, et al. Reference values for exercise limitations among adults with congenital heart disease. Relation to activities of daily life—single centre experience and review of published data. Eur Heart J 2012;33:1386–96. [8] Reybrouck T, Mertens L. Physical performance and physical activity in grown-up congenital heart disease. Eur J Cardiovasc Prev Rehabil 2005;12:498–502. [9] Dua JS, Cooper AR, Fox KR, Graham Stuart A. Exercise training in adults with congenital heart disease: feasibility and benefits. Int J Cardiol 2010;138:196–205. [10] Karmisholt K, Gyntelberg F, Gotzche PC. Physical activity for primary prevention of disease. Systematic reviews of randomised clinical trials. Dan Med Bull 2005;52:86–9. [11] Fricke O, Witzel C, Schickendantz S, Sreeram N, Brockmeier K, Schoenau E. Mechanographic characteristics of adolescents and young adults with congenital heart disease. Eur J Pediatr 2008;167:331–6. [12] Greutmann M, Lan Le T, Tobler D, et al. Generalised muscle weakness in young adults with congenital heart disease. Heart 2011;97:1164–8. [13] Witzel C, Sreeram N, Coburger S, Schickendantz S, Brockmeier K, Schoenau E. Outcome of muscle and bone development in congenital heart disease. Eur J Pediatr 2006;165:168–74. [14] World Medical Association I. 2011. [15] Cider A, Carlsson S, Arvidsson C, Andersson B, Sunnerhagen KS. Reliability of clinical muscular endurance tests in patients with chronic heart failure. Eur J Cardiovasc Nurs 2006;5:122–6. [16] Sunnerhagen KS, Hedberg M, Henning GB, Cider A, Svantesson U. Muscle performance in an urban population sample of 40- to 79-year-old men and women. Scand J Rehabil Med 2000;32:159–67. [17] Rolyan SP. Jamar hydraulic hand dynamometer owner's manual. The recognized standard for the measurement of hand grip strength. Bolingbrook. p. 1–9. [18] Mathiowetz V, Weber K, Volland G, Kashman N. Reliability and validity of grip and pinch strength evaluations. J Hand Surg Am 1984;9A:22–6. [19] Ruuska J, Sommansson J, Svantesson U, Magnusson E, Hultenheim Klintberg I. Reference values for isometric shoulder strength and correlation between strength and BMI. Level of activity and age. [master's thesis] Gothenburg: Institute of Neuroscience and Physiology. University of Gothenburg; 2005 [20 pp.]. [20] Leggin B, Neuman R, Iannotti J, Williams G, Thompson E. Intrarater and interrater reliability of three isometric dynamometers in assessing shoulder strength. J Shoulder Elbow Surg Jan–Feb 1996;5:18–24. [21] The Criteria Committee of the New York Heart Association. Nomenclature and criteria for diagnosis of diseases of the heart and great vessels. 9th ed. Boston: Little, Brown & Co.; 1994. [22] Bennett JA, Riegel B, Bittner V, Nichols J. Validity and reliability of the NYHA classes for measuring research outcomes in patients with cardiac disease. Heart Lung 2002;31:262–70. [23] Ekman I, Cleland JG, Andersson B, Swedberg K. Exploring symptoms in chronic heart failure. Eur J Heart Fail 2005;7:699–703. [24] Gratz A, Hess J, Hager A. Self-estimated physical functioning poorly predicts actual exercise capacity in adolescents and adults with congenital heart disease. Eur Heart J 2009;30:497–504. [25] Willmore J, Costhill D. Physiology of sport and exercise. 2nd ed. Champaign: Human Kinetics; 1999. [26] Clark CJ, Cochrane LM, Mackay E, Paton B. Skeletal muscle strength and endurance in patients with mild COPD and the effects of weight training. Eur Respir J 2000;15:92–7. [27] Sunnerhagen KS, Cider A, Schaufelberger M, Hedberg M, Grimby G. Muscular performance in heart failure. J Card Fail 1998;4:97–104. [28] Lamhonwah AM, Bear CE, Huan LJ, Kim Chiaw P, Ackerley CA, Tein I. Cystic fibrosis transmembrane conductance regulator in human muscle: dysfunction causes abnormal metabolic recovery in exercise. Ann Neurol 2010;67:802–8. [29] Longmuir P, Russell J, Corey M, Faulkner G, McCrindle B. Factors associated with the physical activity level of children who have the Fontan procedure. Am Heart J 2011;161:411–7. [30] Swan L, Hillis WS. Exercise prescription in adults with congenital heart disease: a long way to go. Heart 2000;83:685–7. [31] Pryor JP. Physiotherapy for respiratory and cardiac problems. London: Elsevier; 2008. [32] Fisher LR, Cawley MI, Holgate ST. Relation between chest expansion, pulmonary function, and exercise tolerance in patients with ankylosing spondylitis. Ann Rheum Dis 1990;49:921–5. [33] Schieve LA, Boulet SL, Kogan MD, Van Naarden-Braun K, Boyle CA. A populationbased assessment of the health, functional status, and consequent family impact among children with Down syndrome. Disabil Health J 2011;4:68–77.
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International Journal of Cardiology journal homepage: www.elsevier.com/locate/ijcard
Muscle function in adults with congenital heart disease☆ Linda Ashman Kröönström a,d,⁎, Linda Johansson a, Anna-Klara Zetterström a, Mikael Dellborg b,c, Peter Eriksson b,c, Åsa Cider a,d a
Physical therapy department, Sahlgrenska University Hospital, University of Gothenburg, Gothenburg, Sweden ACHD Unit, Sahlgrenska University Hospital, University of Gothenburg, Gothenburg, Sweden Institute of Medicine, University of Gothenburg, Gothenburg, Sweden d Institute of Neuroscience and Physiology/Physiotherapy, University of Gothenburg, Gothenburg, Sweden b c
a r t i c l e
i n f o
Article history: Received 27 June 2013 Received in revised form 18 October 2013 Accepted 2 November 2013 Available online 13 November 2013 Keywords: Muscle function ACHD Muscle strength Muscle strength dynamometer NYHA
a b s t r a c t Background: The aim was to assess muscle function in a sample of Swedish adult men and women with congenital heart disease (ACHD) and to compare the results with published reference values in healthy adults. Methods and results: From April 2009 to December 2010, 762 adult outpatients were assessed for their suitability and individual need for tests of physical fitness. The patients performed five muscle function tests, two isotonic tests and three isometric tests. Of the 762 patients, 315 (41.3%) patients performed the tests. Patients with ACHD had lower isotonic muscle function compared to healthy reference values. In the heel lift test, men with ACHD performed at 63% and women at 58% of the healthy reference values and in the shoulder flexion test the corresponding performance level was 60% for men with ACHD and 85% for the women. Multiple regression analyses showed that NYHA class II–IV was a significant predictor for a lower isotonic muscle function i.e. heel lift in women (p b 0.001) and men (p = 0.05) and in shoulder flexion (p b 0.001) in women, as well as in isometric knee extension (p = 0.04) and isometric shoulder abduction (p b 0.001) in women. Conclusion: This is the first report of muscle function in a broad and unselected group of patients with ACHD. Our data shows that patients with ACHD have lower isotonic muscle function. The impacts of low muscle function in activities of daily living and the question of whether muscle function could be improved with exercise training need further investigation. © 2013 Elsevier Ireland Ltd. All rights reserved.
1. Introduction Due to improvements in care, an increasing number of adults with congenital heart disease (ACHD) reach adulthood [1]. ACHD is one of the most common malformations with an incidence of slightly less than 1% of live births. The variation in clinical presentation is large, some malformations presenting themselves within a few hours or days after birth, others later in life [2]. In Sweden there are approximately 25,000–30,000 patients with ACHD, all degrees of severity included, and as in many other countries, the population of patients with ACHD is now most likely larger than the population of children with CHD [3]. In general, physical activity is recommended for most, if not all, patients with acquired heart disease, as well as for primary prevention. On a similar note, the European Society of Cardiology states that regular exercise at recommended levels can be performed and should be
☆ The authors take responsibility for all aspects of the reliability and freedom from bias of the data presented and their discussed interpretation. ⁎ Corresponding author at: Physical therapy department, Sahlgrenska University Hospital, University of Gothenburg, Gothenburg, Sweden. Tel.: + 46 31 3434463; fax: + 46 31 3434469. E-mail address: [email protected] (L.A. Kröönström). 0167-5273/$ – see front matter © 2013 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijcard.2013.11.014
encouraged in all patients with ACHD [4]. Several studies have shown that these patients have a lower aerobic capacity, than healthy individuals [5–7]. However, the precise reasons for this are not clear. The lower aerobic exercise capacity could be caused by the congenital lesion per se or by the postoperative anatomical- and physiological conditions, for example reduced ventricular function, or reduced preload due to increased pulmonary vascular resistance [7]. Anxiety and fear of being physically active could also be contributory factors. Overprotection not only from parents, school, and friends but also from physicians and nurses is probably quite common [8]. This will lead not only to reduced exercise capacity but also to lower levels of physical activity, as compared to healthy individuals [9]. A low level of physical activity is a risk factor for developing other health problems [8] such as diabetes, obesity and acquired cardiovascular diseases [10]. Regular physical activity, on the other hand, is associated with a range of health benefits such as improved mental health, decreased rate of anxiety and depression, and improved self-esteem [9]. Apart from the underlying heart malformation, a lower level of physical activity and a non-exercising lifestyle per se can reduce aerobic exercise capacity. In other populations, low aerobic exercise capacity has been shown to be associated with poor muscle function. Although levels of physical activity and aerobic exercise capacity have been studied in patients with ACHD, little is known about these patients' muscle
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function. A lower maximal hand grip has been reported [11,12], while others have found a normal muscle and bone development (in proportion to the patient's height) in adolescents and young adults with congenital heart disease [13]. We observed in some patients what seemed to be a relationship between poor muscle function and symptoms such as pain and weakness and therefore decided to assess muscle function. The overall aim of the study was thus to assess muscle function in a sample of Swedish adult men and women with ACHD and to compare the results with published reference values in healthy adults.
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2.4.3.1. Reference group. The results of the patients with ACHD were compared to reference values in the Jamar — Hydraulic Hand dynamometer owner's manual [17]. Reference values were available for ages 6–75 years. Inter- and intra-rater reliability is good for this instrument [18].
2.4.4. Unilateral isometric knee extension Knee extension was assessed with IsoForce Control® (Medical Device Solutions, Oberburg, Switzerland), which is a portable isometric dynamometer measuring static muscle strength. The patient sat on a stool, back touching the wall, with the testing leg in 90° knee flexion, with a strap around the dominant leg just over the malleolus. The other leg was stretched forward with the heel touching the floor.
2. Patients and methods The adult congenital heart unit (ACHD unit) at Sahlgrenska University Hospital/Östra serves a population of 1.5 million and is the only complete unit within that area. Adult patients with known ACHD are seen at that unit and children within the catchment area are referred to the unit when they reach 18 years of age. 2.1. Study population From April 2009 to December 2010, all outpatients with ACHD seen at regular visits in our ACHD unit were assessed for potential contraindications and, if none were present, the patient was referred to see a specially trained physiotherapist connected to the ACHD unit. 2.2. Exclusion criteria The exclusion criteria were severe arrhythmias, patients due to undergo surgery, advanced heart failure, severe cerebral lesions, or intellectual disabilities that made it difficult to perform the muscle function tests. Patients were given verbal and written information about the study and signed a letter of informed consent. The study was approved by the local ethics committee and followed the ethical guidelines of the 1975 Declaration of Helsinki [14]. 2.3. Reference group A description of the reference values used to compare with the results of patients with ACHD will be presented after the description of each muscle function test. 2.4. Measurements Measurements were chosen to evaluate muscle function in upper and lower extremities as well as isotonic and isometric muscle functions. The patients performed five muscle function tests, two isotonic and three isometric tests, in the following order: isotonic shoulder flexion, isometric handgrip strength, isotonic heel lift, isometric shoulder abduction, and isometric knee extension. All three isometric tests were performed three times with approximately 30 seconds' rest between trials. Standardized instructions were given by the physiotherapists leading the test. No verbal encouragement was used during the tests but instructions to undertake all of the tests with maximum effort were given in advance. 2.4.1. Unilateral isotonic shoulder flexion The patient sat on a stool, back touching the wall, and held a weight in the hand of the arm to be tested (3 kg for men and 2 kg for women). The patient was asked to elevate the testing arm, from 0 to 90° flexion, as many times as possible at the speed of 20 contractions per minute using a metronome (Wittner Taktell Piccolo, Germany).
2.4.4.1. Reference group. No reference values were available. The reliability of this test has not been evaluated.
2.4.5. Unilateral isometric shoulder abduction Shoulder abduction was assessed with IsoForce Control® (Medical Device Solutions, Oberburg, Switzerland), which is a portable isometric dynamometer measuring static muscle strength. The patient sat on a stool, back touching the wall, legs stretched forward and crossed with one heel touching the floor. The patient's arm was elevated to 90° in the scapula direction and a strap was placed around the wrist (styloid process) on the dominant arm.
2.4.5.1. Reference group. The results of the patients with ACHD were compared to healthy reference values of 19–57 year olds [19]. IsoForce has been tested for intra-rater and inter-rater reliability [20].
2.5. Statistical methods Data were analyzed using Statistical Package for Social Sciences (SPSS) 17.0 for Windows (Chicago, Illinois, USA). Demographic data are presented as mean value and one standard deviation (SD). The Independent-samples T-test was used for comparison of muscle function between patients with ACHD and reference values. Muscle function is presented as percent of reference values. Age-adjusted reference values were used for two of the isometric tests [17,19]. Diagnosis groups were formed based on the categories used by the Swedish national adult congenital heart registry. To form larger groups, these categories were combined into the following three groups: Less complicated, Corrected and Complex diagnosis. Less complicated diagnosis consisted of simple shunts, aortic valve malformations, aortic anomalies, mitral valve lesions, pulmonary valve lesions and tricuspidalis valve lesions. Corrected diagnosis consisted of right ventricular/tetralogy of Fallot and transposition of the great arteries. Complex diagnosis consisted of truncus arteriosus, univentricular repair and others. This arbitrary division was made to investigate whether differences in muscle function could be related to degree and severity of malformations and to facilitate statistical analysis. The type of multiple regression used was Enter and was used to assess the association between muscle function, sex, age, the functional classification system of the New York heart Association (NYHA) [21] and different diagnosis groups. NYHA was dichotomized into two groups, NYHA I and NYHA II–IV. Tests were two-sided and the pvalue was set to b 0.05.
3. Results 3.1. Recruitment and demographics
2.4.1.1. Reference group. The results of the patients with ACHD were compared to healthy men and women aged 60 or above. This test shows good test–retest reliability [15]. 2.4.2. Unilateral isotonic heel lift Heel lifts are performed on a 10° wedge, one lift every other second using a metronome (Wittner Taktell Piccolo, Germany). Patients were allowed to touch the wall for balance and on each rise the head had to touch a marker on a measuring stick that was calibrated in advance. The contralateral foot was held slightly above the floor. The test was terminated if the knee on the tested leg was bent or if it was impossible for the patient to follow the pace. The number of maximal heel lifts was registered for each leg. 2.4.2.1. Reference group. The results of the patients with ACHD were compared to an urban population sample of men and women aged from 40 to 79 years [16]. This test has good test–retest reliability [15]. 2.4.3. Isometric handgrip strength Handgrip strength was measured with Jamar® (Sammons Preston Rolyan, Chicago, USA), which is a hydraulic dynamometer measuring maximum handgrip strength in the cylindrical grip. The patient was seated on a chair without armrests, shoulder adducted, and the elbow of the hand tested was held at 90°.
Seven hundred and sixty-two outpatients seen at a specialized ACHD unit were assessed and screened for their suitability and individual need for tests of physical function. The demographics of this population are given in Table 1. Three hundred and fifteen (41.3%) patients performed the tests. Four hundred forty seven (58.7%) patients did not perform the tests for one of the following reasons: declined to participate, psychiatric disorders, unstable or severe cardiac condition, musculoskeletal disorders, intellectual or cerebral disability, pregnancy, discontinuation of planned care (i.e. moving outside the catchment area) or other or unknown reasons. A flowchart of the patient recruitment is presented in Fig. 1. Of the 315 (41.3%) patients, 161 were men (51.1%) and 154 were women (48.9%), see Table 2. Age ranged from 18 to 75 years and the mean age was 34 years. The NYHA class of all patients was determined. No significant differences were seen in patients who performed the tests, in comparison to patients who declined to participate or who for other reasons did not perform the tests, see Table 1.
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Table 1 Descriptive data of all patients, n = 762.
Age, in years: mean (SD) Men n (%) Women n (%) Diagnosis group: Less complicated n (%) Corrected n (%) Complex n (%) NYHA class: I/II/III/IV n (%)
Table 2 Descriptive data of included patients, n = 315.
Included patients
Not included patients
p-Value Sex difference
34 (13) 161 (51%) 154 (49%)
36 (15) 226 (50.6%) 221 (49.4%)
ns ns
234 (74.3%) 67 (21.3%) 14 (4.4%) 256 (81.5%) 47 (15%) 11 (3.5%) 0
354 (79.2%) 76 (17%) 17 (3.8%) 341 (78.4%) 74 (17%) 17 (3.9%) 3 (0.7%)
ns
ns
Less complicated diagnosis consisted of simple shunts, aortic valve malformations, aortic anomalies, mitral valve lesions, pulmonary valve lesions and tricuspidalis valve lesions. Corrected diagnosis consisted of right ventricular/tetralogy of Fallot and transposition of the great arteries. Complex diagnosis consisted of truncus arteriosus, univentricular repair and others.
3.2. Muscle function, comparison of groups based on functional classification (NYHA) and diagnostic group Results of the isometric muscle function tests are presented in Table 3 and results of the isotonic muscle function tests are presented in Figs. 2 and 3. While isometric muscle function appeared to be similar to reference values, isotonic muscle function in both the upper and lower parts of the body was poorer (Figs. 2 and 3). In
Age, in years, mean (SD) Diagnosis group: Less complicated n (%) Corrected n (%) Complex n (%) NYHA I n (%) NYHA II n (%) NYHA III n (%) NYHA IV n (%) Reconstructive cardiac surgery n (%) Smokers n (%) Medication n (%) Beta-blockers n (%) ACE inhibitors n (%) Warfarin n (%) Aspirin n (%) Diuretics n (%) Angiotensin 2 blockers n (%) Aldosterone inhibitors n (%) Digitalis n (%) Other n (%)
Men, n = 161
Women, n = 154
p-Value
33 (12)
36 (14)
0.022
115 (71.4%) 40 (24.8%) 6 (3.7%) 142 (88.2%) 15 (9.3%) 4 (2.5%) 0 134 (84.8%) 14 (9%) 76 (49.4%) 42 (29.2%) 22 (15.3%) 22 (15.3%) 12 (8.3%) 10 (6.9%) 4 (2.8%) 0 (0%) 3 (2.1%) 4 (3.3%)
119 (77.3%) 27 (17.5%) 8 (5.2%) 114 (74.5%) 32 (20.9%) 7 (4.6%) 0 113 (74.8%) 14 (9.3%) 71 (47.7%) 31 (22%) 14 (9.9%) 17 (12.1%) 22 (15.6%) 10 (7.1%) 2 (1.4%) 0 (0%) 3 (2.2%) 6 (5.2%)
0.256
0.007
0.029 0.913 0.767 0.165 0.174 0.429 0.058 0.961 0.424 0.993 0.474
Less complicated diagnosis consisted of simple shunts, aortic valve malformations, aortic anomalies, mitral valve lesions, pulmonary valve lesions and tricuspidalis valve lesions. Corrected diagnosis consisted of right ventricular/tetralogy of Fallot and transposition of the great arteries. Complex diagnosis consisted of truncus arteriosus, univentricular repair and others.
the heel lift test, men with ACHD performed at 63% and women performed at 58% of the healthy reference values. In the shoulder flexion test, men with ACHD performed at 60% and the women at 85% of the healthy reference values. The multiple regression analyses showed that age has a significant negative impact on muscle function in knee extension in women (p = 0.01), and shoulder abduction (p = 0.05) and the heel lift in men (p b 0.001), see Table 4. Higher NYHA class II–IV was a significant predictor for a decrease in isotonic muscle function, i.e. heel lift in women (p b 0.001) and men (p = 0.05) and shoulder flexion (p b 0.001) in women. Furthermore, NYHA class II–IV significantly predicted lower isometric knee extension (p = 0.04) and isometric shoulder abduction (p b 0.001) in women. No other significant results were seen when comparing muscle function in relation to NYHA class. There were no significant differences in muscle function for the three diagnosis groups. 4. Discussion
Fig. 1. Patient recruitment.
This study shows that patients with ACHD have significantly reduced isotonic muscle function compared to healthy reference values. Our results also show lower muscle function, in several muscle groups, in relation to severity of NYHA class. Though NYHA classification is widely used within research in cardiology, its validity, reliability and sensitivity are less well documented in the current setting [22]. There are reports indicating a “difference in patients' self-assessed functional classification compared to investigators' reported NYHA classification” [23] and Gratz et al. have stressed the importance of testing all patients' level of physical fitness [24], as patients with ACHD may underestimate their symptoms due to “never having experienced unimpaired physical exertion as their healthy counterparts have”. Furthermore, patients with ACHD may have made lifelong psychosocial adaptations on the basis of their congenital defects, and may thus consider their situation to be normal [24]. This study found no relation between diagnosis groups and muscle function. Our results show a lower muscle function, in a few muscle groups as a function of age, which is coherent with the results of other
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Table 3 Isometric muscle function test in patients with congenital heart disease. Variable
All patients
Shoulder abduction, kg, mean (SD) Knee extension, kg, mean (SD) Handgrip, kg, mean (SD)
6.9 (2.8) n = 290 23.5 (7.7) n = 286 37.2 (16.8) n = 221
a
% of reference value a n.a
Men
% of reference valuea
Women
% of reference valuea
p-Value Sex difference
8.7 (2.6) n = 147 26.4 (7.2) n = 143 46 (16) n = 114
96% n.a 90%
5.1 (1.6) n = 143 20.6 (7.2) n = 143 27.9 (11.9) n = 107
109% n.a 87%
b0.001 b0.001 b0.001
Percent of age-adjusted reference value. n.a = not available.
authors [16]. Furthermore, men had better muscle strength than women, which is also in accordance with the results of other authors [16,25]. Lower muscle function has been found in several other diagnoses such as chronic obstructive pulmonary disease [26] and chronic heart failure (CHF) [27]. Skeletal muscle weakness has also been seen in other congenital diseases such as cystic fibrosis [28]. As muscle function is lower in the above mentioned congenital diseases, it may be surmised that a physically inactive lifestyle contributes to the lower muscle function. For example, in patients with the Fontan procedure, physical activity is primarily associated with factors unrelated to cardiac status [29]. Even though muscle function has been studied for many other diagnoses, it has scarcely been assessed in patients with ACHD. The isotonic muscle function tests used in this study were developed as a method to test muscles and muscle function used in activities of daily living [15]. Patients with CHF have also been found to have significantly lower isotonic endurance in shoulder flexion and heel lift [15]. It is well known that one of the major symptoms in patients with CHF is decreased muscle function [27]. Studies of patients with CHF show decreased muscle function in isotonic muscular endurance, possibly due to maladaptation in skeletal muscle fibers
together with low levels of physical activity [15]. An important contributing factor to impaired physical fitness is an inactive lifestyle, as often observed in patients with ACHD. It has been claimed that this could be the result of overprotection by parental or environmental overprotection [8]. One article showed that adequate discussions with the patient of the importance of fitness and the prescription of an individually tailored exercise program were rare. In 71% of cases, the topic of exercise had not been spontaneously raised by the pediatrician, the general practitioner, or the cardiologist at the adult clinic [30]. In Sweden (at the above-mentioned ACHD unit) patients with ACHD have not routinely been given the opportunity to seek treatment from a physiotherapist, yet the advantages of physiotherapy connected with an ACHD-unit are many. Given the wide variety of diagnosis with different degrees of severity, the changes in symptoms over time and the fact that patients with ACHD often require lifelong follow-up, both patients and medical staff benefit from a close cooperation. During this study no heart-related incidents or incidents concerning musculoskeletal problems occurred. The prevalence of incidents during tests of physical fitness for patients with ACHD is unknown. Cumulative medical experience has shown that patients with ACHD have a very low risk of incidents
Fig. 2. Isotonic muscle function test: heel lift test in patients with ACHD compared to healthy reference values.
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Fig. 3. Isotonic muscle function test: shoulder flexion test in patients with ACHD compared to healthy reference values.
during exercise [8]. Despite this, it is necessary to have access to equipment and training for cardiac and pulmonary resuscitation (CPR) when testing patients with ACHD [31]. The relationship between muscle function, congenital heart disease and level of physical activity is not clear. Whether the lower muscle function is due to physical inactivity or maladaptation in skeletal muscle fibers, is yet to be discovered. No exercise studies have been found that investigate training of muscle function. The mean age of the patients in this study was 34 years. Considering that muscle function is significantly lower at this age compared to healthy individuals, one will have to take into consideration the consequences if the patient's muscle function continues to decrease. Further studies in patients with ACHD should focus on whether muscle function can increase with training. One possibility is to prescribe individually tailored exercise programs to maintain or increase muscle function for patients with ACHD as part of their regular visits to the ACHD unit.
lack of tests of reliability data regarding this test. One other limitation of this study was that there was not one single group of reference values with which it was possible to compare all tests of muscle functions with. A group of healthy individuals who had all performed the same tests would have been preferred. In this study, tests of muscle function were compared to various available reference values [15–17,19]. Reference values for the isotonic muscle function tests were obtained for controls substantially older than the present patient population and the difference between patients and controls may therefore have been underestimated. The patients who declined to participate did not differ from the participants concerning age, NYHA class or diagnosis group. However, the level of physical activity is not known and therefore one cannot know if these patients choose not to participate because of high or low levels of physical activity and training, nor whether they had a similar activity level to the participants.
4.1. Limitations of the present study 5. Conclusions There are certain problems in trying to assess a person's muscle function: firstly, there is unfamiliarity among patients with the form of muscle function tests; secondly, there is the problem of patient motivation, as some patients will push themselves closer to their maximum working capacity than others [32]. One aspect to take into consideration is the familiarization effect. The three tests of isometric strength were all carried out three times each and a mean value was calculated, which would minimize the risk of the familiarization effect and therefore gave a more valid result. The verbal communication between the patient and the investigator is also important. Therefore, verbal communication was standardized and no encouragement was given during the tests. In this group of patients, including some cases of mental retardation, such as in patients with Down's syndrome [33], it is especially important to ensure that the instructions are as clear as possible. One limitation of the study is the lack of reference values for the knee extension test, as well as
Our data shows that patients with ACHD have a lower isotonic muscle function compared to reference values. The impact of the lower muscle function in activities of daily living and the question of whether muscle function could be improved with exercise training need further investigation.
Acknowledgments The authors wish to thank Georgios Lappas for help with statistical advice and the Research and Development of Region Västra Götaland, the Heart and Lung Foundation and ALF-LUA funds for economic support. The authors of this manuscript have certified that they comply with the Principles of Ethical Publishing in the International Journal of Cardiology.
L.A. Kröönström et al. / International Journal of Cardiology 170 (2014) 358–363 Table 4 Age, NYHA, diagnosis groups and sex and their influence on the five different muscle function tests. Sex
Test of muscle function
Variable
Estimate
Lower limit
Upper limit
p-Value
M
Knee extension
Age Corrected Complex NYHA II/II/IV Age Corrected Complex NYHA II/II/IV Age Corrected Complex NYHA II/II/IV Age Corrected Complex NYHA II/II/IV Age Corrected Complex NYHA II/II/IV Age Corrected Complex NYHA II/II/IV Age Corrected Complex NYHA II/II/IV Age Corrected Complex NYHA II/II/IV Age Corrected Complex NYHA II/II/IV Age Corrected Complex NYHA II/II/IV
−0.04 −1.13 3.43 0.40 −0.11 0.98 −2.72 −3.11 −0.04 −0.93 0.44 0.03 −0.02 −0.34 0.17 −1.21 0.12 −4.48 3.06 −6.14 0.06 −4.37 −4.36 −4.32 −0–20 −3.00 −3.17 −5.10 −0.04 −0.18 1.26 −7.81 0.04 −4.06 −6.56 −9.45 0.16 −1.60 −2.42 −22.92
−0.14 −3.99 −2.66 −3.58 −0.20 −2.10 −8.41 −6.12 −0.07 −1.93 −1.72 −1.43 −0.04 −1.03 −1.10 −1.88 −0.15 −11.94 −13.29 −16.82 −0.12 −10.32 −15.33 −10.65 −0.32 −6.58 −11.00 −10.21 −0.16 −3.97 −5.89 −11.63 −0.21 −11.33 −22.67 −19.65 −0.27 −16.43 −30.60 −37.30
0.06 1.72 9.52 4.38 −0.02 4.06 2.98 −0.10 0.00 0.07 2.61 1.49 0.00 0.35 1.44 −0.54 0.38 2.98 19.41 4.54 0.25 1.58 6.62 2.02 −0.07 0.59 4.67 0.00 0.07 3.60 8.41 −3.99 0.30 3.21 9.54 0.75 0.59 13.23 25.76 −8.53
0.42 0.43 0.27 0.84 0.01 0.53 0.35 0.04 0.05 0.07 0.69 0.97 0.09 0.33 0.79 0.00 0.38 0.24 0.71 0.26 0.51 0.15 0.43 0.18 0.00 0.10 0.43 0.05 0.46 0.92 0.73 0.00 0.75 0.27 0.42 0.07 0.46 0.83 0.87 0.00
F
M
Shoulder abduction
F
M
Handgrip
F
M
Heel-lift, right
F
M
Shoulder flexion
F
M = male, F = female, Diagnosis group: Less complicated/Corrected/Complex.
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