African Journal for Physical, Health Education, Recreation and Dance (AJPHERD)
Vol. 17, No. 4 (December: 1) 2011, pp. 581-590.
Prevalence of risk factors for sudden cardiac death in competitive South African student athletes A. BAKKUM1, C. BRESLER1, L. NORTIE1, I. SHAW2&3 AND B.S. SHAW3 1
Department of Sport and Movement Studies, University of Johannesburg, P.O. Box 524, Auckland Park, Johannesburg, Gauteng, 2006, Republic of South Africa 2 Office of the Deputy Pro Vice-Chancellor: Research, Monash South Africa, P.O. Box X60, Ruimsig, 1725, Republic of South Africa. 3 Department of Sport, Rehabilitation and Dental Sciences, Tshwane University of Technology, Private Bag X680, Pretoria, Gauteng, 0001, Republic of South Africa; E-mail;
[email protected] (Received 05 January 2011; Revision Accepted 28 September 2011)
Abstract Due to the increasing incidence of sudden cardiac death in athletes, there is an increasing need to adequately pre-screen and identify athletes at risk for cardiac events/disease. Sixty University of Johannesburg (UJ) athletes were drawn randomly from the UJ athletic department (30 males and 30 females) and analyzed using personal and family history, physical examination (including blood pressure, fasting cholesterol and glucose measures) and 12-lead resting electrocardiography to detect pre-existing cardiac risk or disease. The study detected that cardiac risk factors were present in 29 participants (48.35%) of which 18 were female and 11 male. Irregular heart rhythms were the most prevalent cardiac risk in both males and females with a family history of cardiovascular disease the second most prevalent amongst both males and females. Significant correlations were found between gender and family history of cardiovascular disease (r = 0.377; p = 0.008) and gender and tachyarrythmias (r = - 0.364; p = 0.012). Although participation in sport represents a cardioprotective benefit it does not preclude the prevalence of risk factors and disease in athletes. The study indicates that pre-participation screening may prove to be an integral intervention strategy to minimize the incidence of sudden cardiac death in athletes but should be used with caution especially pertaining to the reliability of ECG interpretations. Keywords: Cardiovascular disease, college, medical history, sudden cardiac death, sport. How to cite this article: Bakkum, A., Bresler, C., Nortie, L., Shaw, I. & Shaw, B.S. (2011). Prevalence of risk factors for sudden cardiac death in competitive South African student athletes. African Journal for Physical, Health Education, Recreation and Dance, 17(4:1), 581-590.
Introduction The topic of sudden cardiac death in the young and presumably physically fit athletes has attracted increasing attention due to sudden and unexpected catastrophes in young trained athletes (Basavarajaiah, Shah & Sharma, 2006; Maron, 1993). This is so since these events were once regarded as rare tragedies or unfortunate accidents and are increasing at a rate of 6% per annum in the United States of America (Maron, Doerer, Hass, Tierney, Mueller, 2009). However, the precise frequency of these deaths is unknown (Maron, 1998). While young competitive athletes are widely regarded as a special subgroup of
582 Bakkum, Bresler, Nortie, Shaw and Shaw healthy individuals with a unique lifestyle who are seemingly invulnerable and often capable of extraordinary physical achievement (Maron, 1993), the increasing incidence of sudden cardiac death in athletes has inverted the common misconception that physically fit individuals are not at risk of developing cardiovascular disease (Maron, 2003). Unfortunately, sudden cardiac death is most often the first clinical manifestation of an underlying or undiagnosed structural or electrical anomaly or cardiovascular disease and usually occurs in previously asymptomatic athletes (Corrado et al., 2011; Drezner & Corrodao, 2011). Most often the cause of sudden cardiac death in athletes is related to hypertrophic cardiomyopathy and several congenital coronary artery abnormalities, while arrhythmogenic right ventricular dysplasia may be a more common cause of sudden cardiac death than previously suspected (Maron, 1998). Only about 10% of the sudden cardiac deaths reported are young women athletes (Maron et al., 1996b), possibly due to lower participation rates of women, different training demands and/or cardiac adaptation (Maron, 1998; Maron et al., 1996a). Further, hypertrophic cardiomyopathy is also less commonly clinically diagnosed in women. These observations also suggest the possibility that a measure of protection from sudden cardiac death is attributable in some way to gender. Nevertheless, available data does not provide sufficient information regarding the prevalence of pre-existing cardiac risk or cardiovascular disease in athletes and does not provide a compelling justification to construct specific screening algorithms based on any demographic sub grouping (Maron et al., 1996b). Therefore, the purpose of this study was to identify the prevalence of pre-existing cardiac risk or cardiovascular disease in competitive student athletes and to determine if any differences existed in cardiac risk amongst male and female competitive student athletes. Materials and Methods Sample Sixty University of Johannesburg athletes were drawn randomly from the university‘s athletic department (n = 30 male aged 19-23 years; mean age 21.4 years; n = 30 female aged 19-20 years; mean age 21.37 years). Of the 30 male participants, 22 competed in rugby, three in rowing, two in hockey, one in tennis, one in cross fit and one in basketball. Of the 30 female participants, 22 competed in hockey, six in athletics, one in netball and one in rowing. The participants were required to be current athletes at any of the University of Johannesburg‘s registered sporting clubs as confirmed by the relevant sporting coach and/or manager. The demographics and cardiac risk factors for sudden cardiac death of the participants are presented in Table 1. Prior to participation in the study, all participants gave written informed consent and were allowed to discontinue from the study at any time if they wished. This investigation was approved by the
Prevalence of risk factors for sudden cardiac death 583 Institutional Review Board at the University of Johannesburg in accordance with the ethical standards and the Helenski Declaration of 1975 (revised in 1983) on human experimentation. Table 1: Risk factors for sudden cardiac death in competitive South African student athletes Variables Females (n = 30) Males (n = 30) Age (years)
21.37 ± 2.91
21.40 ± 2.04
124.40 ± 11.83
138.23 ± 12.37
78.33 ± 6.81
87.73 ± 7.85
Glucose (mmol.L-1)
4.70 ± 0.89
5.03 ± 1.24
Cholesterol (mmol.L-1)
4.52 ± 0.69
4.59 ± 0.48
Percentage body fat (%)
20.06 ± 5.95
10.73 ± 3.65
Systolic blood pressure (mmHg) Diastolic
blood
pressure
(mmHg)
Values are means ± standard deviation; mmHg: millimeters mercury; mmol.L-1: millimoles per litre
Cardiac risk assessment All participants underwent the same battery of assessments and were administered by the same technician. Due to the controversy regarding the efficiency, impact of false-positive results and cost-effectiveness of routine screening (Corrado et al., 2011), the particular questionnaires and tests chosen by the present study were as a result of their accessibility, ease of administration and assessment, availability as well as the appropriateness of the data provided in their results with each test providing pre-screening insight into each athlete‘s potential cardiac risk (Maron et al., 2005). All assessments selected comply with the European Society of Cardiology‘s (ESC) recommendation of using personal and family history, physical examination and 12-lead resting ECG (Borjesson & Dellborg, 2011). Participants were required to indicate their cardiac risk by identifying their cardiac risk as suggested by the American Heart Association (AHA) Consensus Panel Recommendations for Pre-participation Athletic Screening (Maron et al., 1996b). This included a family history of premature death or significant disability from cardiovascular disease in close relative(s) younger than 50 years; a family history of premature sudden cardiac death and/or heart disease in surviving relatives less than 50 years old and a personal history of heart murmur, systemic hypertension, fatigue, syncope/near-syncope, excessive/unexplained exertional dyspnea and/or exertional chest pain (Maron et al., 1996b). Resting systolic and diastolic blood pressures were measured by the auscultation method using a stethoscope and sphygmomanometer (Alpk2 Sphygmomanometer, Japan) and classified according to the criteria of Heyward (2006). Participants were measured in the sitting position after five minutes rest respecting the procedures for assessment of resting blood pressure as recommended by the
584 Bakkum, Bresler, Nortie, Shaw and Shaw American College of Sports Medicine (ACSM) (2006). Following a nine- to 12hour fasting period and prior to any exercise, blood samples were drawn using the fingerprick method with each participant in the seated position. Fasting blood cholesterol and glucose concentrations were determined by using the Accutrend® system (Roche Diagnostics, Mannheim, Germany). Anthropometric measurements were carried out according to the methods proposed by the International Society for the Advancement of Kinanthropometry (ISAK) (Norton & Olds, 1996). Percentage body fat (%BF) was calculated from the tricep, subscapular, suprailiac, abdominal, thigh and calf skinfolds using the equation of Carter et al., (1982). Since cardiovascular screening in athletes using electrocardiography (ECG) is routinely practised and endorsed by most major sports and medical associations (Drezner & Corrodao, 2011), the present study used the 12-lead ECG screening, administered by a qualified exercise and rehabilitation specialist and according to the Iredell County EMS ALS Protocols (2007), in this sample of competitive student athletes (Swiatowiec et al., 2009) using commonly accepted criteria to assess the ECG; irregular rhythms, escape, premature beats, tachyarrhythmias, heart block, atrial and ventricular hypertrophy, ischemia, infarction and pericarditis. Statistical analysis Data were analyzed using SPSS Version 14 (SPSS Inc., Chicago, IL, 60606, USA). Data are presented as means ± standard deviations (SD). The Chi square test was used to determine probability at an alpha level of 0.05. In order to determine gender differences in cardiovascular risk and clinical factors, variable and gender cross-tabulation were performed on the data. Symmetric measures were used to determine the phi value to ascertain effect size with r-values of 0.1, 0.3 and 0.5 being seen as small, medium and large effect sizes, respectively (Iman, 1994). Results The distributions of participants with cardiac risk are reflected in Table 2. Specifically, 37 of the 60 participants (61.7%) were found to be at risk in terms of the family history of cardiovascular disease with 24 participants being female (64.9%) and 13 being male (35.1%). Further, cross-tabulation analysis of the data revealed a significant (p ≤ 0.05) relationship between gender and family history of cardiovascular disease (p = 0.008). In this regard, the occurrence of a family history of cardiovascular disease was moderately delineated by gender (r = 0.377; p = 0.003). With regards to hemodynamic variables, 12 participants (20.0%) with three female (25.0%) and nine males (75.0%) presented with stage 1 hypertension while four male participants (6.7%) presented with stage 2 hypertension. Only
Prevalence of risk factors for sudden cardiac death 585 one male participant (1.7%) of the total sample was found to be at risk in terms of hyperglycemia. The results further indicated that of the 60 participants, six participants (10.0%) of which four were female (66.7%) and two male (33.3%) were found to be at risk in terms of hypercholesterolemia. The anthropometric evaluation revealed that out of the 60 participants, one female participant (1.7%) could be classified as overweight, while eight participants (13.3%); six females (75.0%) and two males (25.0%); could be classified as obese. Table 2: Distribution of competitive athletes with cardiovascular disease risk Cardiac risk factor
Females
Males
Males and
Number (% of
Number (% of
females
males and
males and
Number (%
females)
females)
of total of 60 subjects)
Family history of cardiovascular disease†
24 (64.9%)
13 (35.1%)
37 (61.7%)
Hypertensive – Stage 1
3 (25.0%)
9 (75.0%)
12 (20.0%)
Hypertensive – Stage 2
0 (0.0%)
4 (100.0%)
4 (6.7%)
Hyperglycemic
0 (0.0%)
1 (100.0%)
1 (1.7%)
Hypercholesterolemic
4 (66.7%)
2 (33.3%)
6 (10.0%)
Overweight
1 (100.0%)
0 (0.0%)
1 (1.7%)
2 (25.0%)
8 (13.3%)
Obese
6 (75.0%)
ECG – Irregular heart rhythm
24 (55.8%)
19 (42.2%)
43 (71.7%)
ECG – Escapes
2 (50.0%)
2 (50.0%)
4 (6.7%)
ECG - Tachyarrythmias†
11 (84.6%)
2 (15.4%)
13 (21.7%)
ECG – Premature beats
2 (50.0%)
2 (50.0%)
4 (6.7%)
ECG – Atria hypertrophy
1 (25.0%)
3 (75.0%)
4 (6.7%)
ECG – Ventricular hypertrophy
3 (25.0%)
9 (75.0%)
12 (20.0%)
ECG – Heart Blocks
0 (0.0%)
0 (0.0%)
0 (0.0%)
0 (0.0%)
0 (0.0%)
0 (0.0%)
18 (62.1%)
11 (37.9%)
29 (48.4%)
ECG
-
Ischemia,
Infarction
and/or
Pericarditis Total participants with two or more cardiac risk factors †: indicates a gender effect on cardiac risk factor; mmHg: millimeters mercury; mmol.L-1: millimoles per litre ; ECG: Electrocardiograph
586 Bakkum, Bresler, Nortie, Shaw and Shaw Electrocardiographic (ECG) evaluation indicated that 43 participants (71.7%), of which 24 were females (55.8%) and 19 males (42.2%), demonstrated irregular rhythms. However, no significant relationship was found between gender and irregular rhythms (p = 0.252). Further, of the 60 participants, four participants (6.7%); two females (50.0%) and two males (50.0%) were found to be at risk in terms of their escape observed during the ECG evaluation. Further, 13 participants (21.7%), 11 females (84.6%) and two males (15.4%), were at risk in terms of the presence of tachyarrythmias. Cross-tabulation analysis revealed a significant, moderate relationship between gender and tachyarrythmias (r = 0.364; p = 0.005). In terms of premature beats, the results indicated that four participants (6.7%), two females (50.0%) and two males (50.0%), were at an increased cardiac risk. The ECG evaluation revealed that four participants (6.7%) of which one was a female (25.0%) and three male (75.0%), had an increased cardiac risk based on their left and/or right atria hypertrophy presence. Also, 12 participants (20.0%); three female (25.0%) and nine male (75.0%) were found to have left and/or right ventricular hypertrophy. None of the participants were found to present with a heart block, ischemia, infarction and pericarditis during the ECG evaluation that would have increased their cardiac risk. It is evident that irregular heart rhythms, followed by a family history of cardiovascular disease are the most prevalent cardiac risk factors in this sample of competitive male and female athletes. The data also indicated that 29 of the 60 participants (48.35%) had two or more cardiac risk factors. Of these, 18 or 62.1% were female while 11 or 37.9% were male. Discussion Despite regular exercise reducing cardiovascular morbidity and mortality, some athletes have been found to be at an increased risk of sudden cardiac death due to quiescent cardiac anomalies (Papadakis & Sharma, 2009). In this regard, the results may indicate that competitive university athletes may be at a risk of developing cardiac disease in that almost 50% of the participants had more than two primary risk factors. The present study found that irregular heart rhythms, followed by a family history of cardiovascular disease were the most prevalent cardiac risk factors. This is contrary to the study of Matos et al. (2010) which found hypertension to be the most prevalent pre-existing cardiac risk factor in athletes. However, both the present study and the study of Matos et al. (2010) found that both male and female athletes presented with cardiac risk factors. The cardiac risk found among the competitive university athletes in this study could be related to the physiological adaptations and structural cardiac remodeling that can take place through systematic training in endurance or isometric sports. These changes include an increased left ventricular wall thickness, enlarged ventricular and atrial cavity dimensions and calculated
Prevalence of risk factors for sudden cardiac death 587 cardiac mass, in the presence of normal systolic and diastolic function (Pluim et al., 2000). The magnitude of physiologic hypertrophy may also vary among athletes according to the particular type of training. Also, some cardiac irregularities may be as a result of frequent and high intensity athletic training, known as ―athlete‘s heart‖ (Rost, 1992). However, athletes, as in this sample, may still be at risk despite these cardioprotective morphological adjustments due to factors not related to the size and physiological adaptations (Ferreira et al., 2010). Conclusions It is evident that cardiac risk leading to sudden cardiac death of athletes, especially young athletes, remains an important and a prevalent concern. The lack of awareness and uncertainty about the level of risk incurred by apparently healthy young athletes participating in sports is of major concern. While Borjesson and Dellborg (2011) state that cardiac screening without ECG is not cost-effective in itself and may only be marginally better than no screening at all; the use of ECG screening in athletes should be included with caution due to the practicality of false-positive results in addition to the concerns over the feasibility, cost-effectiveness (Borjesson & Dellborg, 2011; Drezner & Corrodao, 2011; Rowland, 2011). As such, a limitation of this study is that changes in the resting ECG as a result of training are common in athletes and can cause difficulties for differential diagnosis (Corrado et al., 2010). In this regard, the European Society of Cardiology (ESC) class the following changes on ECG as training-related in the absence of other distinctive features: sinus bradycardia, 1st degree atrioventricular block, incomplete right bundle block, early repolarization and isolated increased QRS voltages (increased Sokolow-Lyon index) (Corrado et al., 2010). These changes may occur in up to 80% of athletes and the prevalence is highest in endurance athletes with physiological remodeling of the heart, but the changes may also be found in other athletes and are notably more common in men than in women (Basavarajaiah et al., 2008), although this was not the case in the present study. Further, the experience and qualifications of the technician interpreting the ECG data may have resulted in false-positive results. Additionally, the data are derived from one major South African University study and patterns of sudden death etiology may vary among South African universities. Despite the apparent limitations of the present study, the results of the study have critical implications for especially professional athletes and their sport medicine professionals since cardiovascular disease risk may represent the basis for disqualification from competitive sports to reduce the risk of sudden cardiac death (Maron & Pelliccia, 2006). As such, there is a pressing need to minimize the incidence of sudden cardiac death in competitive athletes and a possible
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