Hypertrophic cardiomyopathy and other causes of sudden cardiac death in young competitive athletes, with considerations for preparticipation screening and criteria for disqualification

Complete mitochondrial genomes of patients from Thailand with cardiovascular diseases

Several previous studies have reported that both variation and haplogroups of mitochondrial (mt) DNA were associated with various kinds of diseases, including cardiovascular diseases, in different populations, but such studies have not been carried out in Thailand. Here, we sequenced complete mtDNA genomes from 82 patients diagnosed with three types of cardiovascular disease, i.e., Hypertrophic Cardiomyopathy (HCM) (n = 26), Long Q-T Syndrome (LQTS) (n = 7) and Brugada Syndrome (BrS) (n = 49) and compared these with 750 previously published mitogenome sequences from interviewed normal individuals as a control group. Both patient and control groups are from the same geographic region of northeastern Thailand. We found 9, 2, and 5 novel mutations that were not both damaging and deleterious in HCM, LQTS, and BrS patients, respectively. Haplogroup R9c was significantly associated with HCM (P = 0.0032; OR = 62.42; 95%CI = 6.892-903.4) while haplogroup M12b was significantly associated with LQTS (P = 0.0039; OR = 32.93; 95% CI = 5.784-199.6). None of the haplogroups was found to be significantly associated with BrS. A significantly higher density of mtDNA variants in the rRNA genes was found in patients with HCM and BrS (P < 0.001) than in those with LQTS or the control group. Effects of detected SNPs in either protein coding or tRNA genes of all the mitogenome sequences were also predicted. Interestingly, three SNPs in two tRNA genes (MT-TA m.5618T>C and m.5631G>A heteroplasmic variants in two BrS patients and MT-TQ m.4392C>T novel homoplasmic variant in a HCM patient) were predicted to alter tRNA secondary structure, possibly leading to abnormal tRNA function.

Exercise recommendations for patients with hypertrophic cardiomyopathy

Individuals with hypertrophic cardiomyopathy (HCM) have historically been advised to limit exercise and sports participation to mild-intensity activities due to concerns for sudden cardiac arrest (SCA). However, more contemporary data have shown SCA is rare in patients with HCM and emerging data is shifting towards support for the safety of exercise in this patient population. Recent guidelines endorse exercise in patients with HCM after a comprehensive evaluation and shared-decision making with an expert provider.

[Analysis of sudden cardiac death in competitive athletes, possibilities for reducing cases]

INTRODUCTION

Sudden cardiac death in athletes is rare (0.5 to 1 per 100 000 athlete years), but sudden cardiac death in known athletes causes general shock.

OBJECTIVE

Our research aim was to collect and study as many sudden cardiac death cases as possible, judge the role of stress and look for ways to reduce fatal tragedies.

METHOD

From registers and newspaper articles found on the Internet, we collected 360 (including 14 women) athletes' sudden cardiac death cases where the sport, age and place of death (during training/competition/after) could be determined. From these, a single database has been prepared in order of the year of death. The cases were grouped and analyzed by sports. Based on our results and literature data, we made recommendations to reduce fatalities.

RESULTS AND CONCLUSION

There were more sudden cardiac deaths in competitions than in trainings (239 vs. 99), but tragedies also happened during warm-ups and chess without physical exertion, furthermore, there was no sudden cardiac death in the stakeless training of marathon/half marathon/triathlon athletes; all these prove the role of stress, so we recommend a psychological conversation before a high-stakes race. There were also a lot of sudden cardiac deaths (79/360) during team sports trainings, so we recommend reanimation readiness there as well. After training/competition, sudden cardiac death happened mainly in sports requiring high static effort, where post-competition monitoring is also recommended. Those who died in training were younger than those who died during the race (p<0.01), so young people should be monitored more closely for medical and (under)fitness. Marathon runners and triathletes were older than team athletes (p<0.005) and only died in competition, so for them a basic examination and an ECG within 1 month before competition are recommended. Conclusions drawn from literature data: sports medicine examination should be standardized and documented in an accessible way; since resuscitation started earlier and professionally is more effective, all competitors should receive reanimation training. Orv Hetil. 2023; 164(29): 1155-1163.

Endurance training-induced cardiac remodeling in a guinea pig athlete's heart model

Besides the health benefits of regular exercise, high-level training-above an optimal level-may have adverse effects. In this study, we investigated the effects of long-term vigorous training and its potentially detrimental structural-functional changes in a small animal athlete's heart model. Thirty-eight 4-month-old male guinea pigs were randomized into sedentary and exercised groups. The latter underwent a 15-week-long endurance-training program. To investigate the effects of the intense long-term exercise, in vivo (echocardiography, electrocardiography), ex vivo, and in vitro (histopathology, patch-clamp) measurements were performed. Following the training protocol, the exercised animals exhibited structural left ventricular enlargement and a significantly higher degree of myocardial fibrosis. Furthermore, resting bradycardia accompanied by elevated heart rate variability occurred, representing increased parasympathetic activity in the exercised hearts. The observed prolonged QTc intervals and increased repolarization variability parameters may raise the risk of electrical instability in exercised animals. Complex arrhythmias did not occur in either group, and there were no differences between the groups in ex vivo or cellular electrophysiological experiments. Accordingly, the high parasympathetic activity may promote impaired repolarization in conscious exercised animals. The detected structural-functional changes share similarities with the human athlete's heart; therefore, this model might be useful for investigations on cardiac remodeling.

Does Regular Physical Activity Improve Personal Income? Empirical Evidence from China

A lack of adequate exercise threatens human health, weakening human capital accumulation. The relationship between exercise and income has become the focus of attention in health economics. In terms of reducing body weight and improving physical fitness, diet and physical exercise are intertwined and become effective ways to shape a healthy state. Based on individual-level survey data from China, this study quantified the economic returns of habitual exercise behavior by using an endogenous switching regression model (ESRM) to eliminate selection bias. The study shows that (1) participants in the group with regular exercise behavior increased their income by 3.79% compared with those not exercising regularly; (2) for the group with no regular exercise behavior, regular exercise increased their income by 13.36% compared with those not exercising regularly. Additionally, empirical evidence shows that both drinking and smoking can significantly increase individual income, despite unhealthy habits. These results suggest that the habit of regular physical activity plays a vital role in increasing individual income and improving overall national health, and the effect of individual behavior on income is affected by national culture. The outcomes are empirical evidence for the Chinese government to promote Healthy China Action and support developing countries worldwide to enable habitual exercise, stimulating a policy of exercise behavior.

FHOD formin and SRF promote post-embryonic striated muscle growth through separate pathways in C. elegans

Previous work with cultured cells has shown transcription of muscle genes by serum response factor (SRF) can be stimulated by actin polymerization driven by proteins of the formin family. However, it is not clear if endogenous formins similarly promote SRF-dependent transcription during muscle development in vivo. We tested whether formin activity promotes SRF-dependent transcription in striated muscle in the simple animal model, Caenorhabditis elegans. Our lab has shown FHOD-1 is the only formin that directly promotes sarcomere formation in the worm's striated muscle. We show here FHOD-1 and SRF homolog UNC-120 both support muscle growth and also muscle myosin II heavy chain A expression. However, while a hypomorphic unc-120 allele blunts expression of a set of striated muscle genes, these genes are largely upregulated or unchanged by absence of FHOD-1. Instead, pharmacological inhibition of the proteasome restores myosin protein levels in worms lacking FHOD-1, suggesting elevated proteolysis accounts for their myosin deficit. Interestingly, proteasome inhibition does not restore normal muscle growth to fhod-1(Δ) mutants, suggesting formin contributes to muscle growth by some alternative mechanism. Overall, we find SRF does not depend on formin to promote muscle gene transcription in a simple in vivo system.

Increased Ca2+ content of the sarcoplasmic reticulum provides arrhythmogenic trigger source in swimming-induced rat athlete's heart model

Sudden cardiac death among top athletes is very rare, however, it is 2–4 times more frequent than in the age-matched control population. In the present study, the electrophysiological consequences of long-term exercise training were investigated on Ca²⁺ homeostasis and ventricular repolarization, together with the underlying alterations of ion channel expression, in a rat athlete's heart model. 12-week swimming exercise-trained and control Wistar rats were used. Electrophysiological data were obtained by using ECG, patch clamp and fluorescent optical measurements. Protein and mRNA levels were determined by the Western immunoblot and qRT-PCR techniques. Animals in the trained group exhibited significantly lower resting heart rate, higher incidence of extrasystoles and spontaneous Ca²⁺ release events. The Ca²⁺ content of the sarcoplasmic reticulum (SR) and the Ca²⁺ transient amplitude were significantly larger in the trained group. Intensive physical training is associated with elevated SR Ca²⁺ content, which could be an important part of physiological cardiac adaptation mechanism to training. However, it may also sensitize the heart for the development of spontaneous Ca²⁺ release and extrasystoles. Training-associated remodeling may promote elevated incidence of life threatening arrhythmias in top athletes.

Cardiac transmembrane ion channels and action potentials: cellular physiology and arrhythmogenic behavior

Cardiac arrhythmias are among the leading causes of mortality. They often arise from alterations in the electrophysiological properties of cardiac cells and their underlying ionic mechanisms. It is therefore critical to further unravel the pathophysiology of the ionic basis of human cardiac electrophysiology in health and disease. In the first part of this review, current knowledge on the differences in ion channel expression and properties of the ionic processes that determine the morphology and properties of cardiac action potentials and calcium dynamics from cardiomyocytes in different regions of the heart are described. Then the cellular mechanisms promoting arrhythmias in congenital or acquired conditions of ion channel function (electrical remodeling) are discussed. The focus is on human-relevant findings obtained with clinical, experimental, and computational studies, given that interspecies differences make the extrapolation from animal experiments to human clinical settings difficult. Deepening the understanding of the diverse pathophysiology of human cellular electrophysiology will help in developing novel and effective antiarrhythmic strategies for specific subpopulations and disease conditions.

Beat-to-beat variability of cardiac action potential duration: underlying mechanism and clinical implications

Beat-to-beat variability of cardiac action potential duration (short-term variability, SV) is a common feature of various cardiac preparations, including the human heart. Although it is believed to be one of the best arrhythmia predictors, the underlying mechanisms are not fully understood at present. The magnitude of SV is basically determined by the intensity of cell-to-cell coupling in multicellular preparations and by the duration of the action potential (APD). To compensate for the APD-dependent nature of SV, the concept of relative SV (RSV) has been introduced by normalizing the changes of SV to the concomitant changes in APD. RSV is reduced by I_Ca, I_Kr, and I_Ks while increased by I_Na, suggesting that ion currents involved in the negative feedback regulation of APD tend to keep RSV at a low level. RSV is also influenced by intracellular calcium concentration and tissue redox potential. The clinical implications of APD variability is discussed in detail.

Nonischemic Left Ventricular Scar as a Substrate of Life-Threatening Ventricular Arrhythmias and Sudden Cardiac Death in Competitive Athletes

Background—

The clinical profile and arrhythmic outcome of competitive athletes with isolated nonischemic left ventricular (LV) scar as evidenced by contrast-enhanced cardiac magnetic resonance remain to be elucidated.

Methods and Results—

We compared 35 athletes (80% men, age: 14–48 years) with ventricular arrhythmias and isolated LV subepicardial/midmyocardial late gadolinium enhancement (LGE) on contrast-enhanced cardiac magnetic resonance (group A) with 38 athletes with ventricular arrhythmias and no LGE (group B) and 40 healthy control athletes (group C). A stria LGE pattern with subepicardial/midmyocardial distribution, mostly involving the lateral LV wall, was found in 27 (77%) of group A versus 0 controls (group C; P<0.001), whereas a spotty pattern of LGE localized at the junction of the right ventricle to the septum was respectively observed in 11 (31%) versus 10 (25%; P=0.52). All athletes with stria pattern showed ventricular arrhythmias with a predominant right bundle branch block morphology, 13 of 27 (48%) showed ECG repolarization abnormalities, and 5 of 27 (19%) showed echocardiographic hypokinesis of the lateral LV wall. The majority of athletes with no or spotty LGE pattern had ventricular arrhythmias with a predominant left bundle branch block morphology and no ECG or echocardiographic abnormalities. During a follow-up of 38±25 months, 6 of 27 (22%) athletes with stria pattern experienced malignant arrhythmic events such as appropriate implantable cardiac defibrillator shock (n=4), sustained ventricular tachycardia (n=1), or sudden death (n=1), compared with none of athletes with no or LGE spotty pattern and controls.

Conclusions—

Isolated nonischemic LV LGE with a stria pattern may be associated with life-threatening arrhythmias and sudden death in the athlete. Because of its subepicardial/midmyocardial location, LV scar is often not detected by echocardiography.

Prevalence of Cardiovascular Disorders Among Iranian Elite Athletes

BACKGROUND

Athletes' health is an important issue and for promoting it, pre-participation examination (PPE) is widely performed by responsible bodies around the world.

OBJECTIVES

This study was to determine prevalence of cardiovascular disorders among athletes participating in the Asian games and answering the question whether the electrocardiogram (ECG) is a necessary part of pre-participation examination (PPE) for prevention of sudden cardiac death.

MATERIALS AND METHODS

All athletes participated at Asian games came to sports medicine federation for a PPE including a comprehensive questionnaire, physical examination and ECG. In this retrospective study all profiles of 338 athletes have been studied as well as their electrocardiograms. Multiple logistic regressions as well as Firth's bias reduction were used with R statistical software and SPSS. For predicting the changes in ECG, receiver operating characteristic (ROC) curve has done.

RESULTS

Among 388 athletes, 80 (20.6%) were female and 308 (79.4%) male with mean age of 23.2 + 8 years. Nine athletes (2.3%) were smokers, 28 of them (7.2%) experienced chest pain and discomfort, 45 of them (13.3%) had palpitations and 28 (7.2%) had history of anemia. Study of their electrocardiograms showed that long Q-T interval was not seen for anyone, but evidence of left ventricular hypertrophy was seen in 12 (3.1%), inverted T wave in 6 (1.5%), and right bundle branch block in 45 (13.3%).

CONCLUSIONS

PPE provides very important information of athletes' health. This study has shown that there was not any significant relation between current examination and electrocardiogram changes but regarding the ECG changes we recommend it as a routine part of PPE.

Association between cardiorespiratory fitness and submaximal systolic blood pressure among young adult men: a reversed J-curve pattern relationship

OBJECTIVES

Exercise blood pressure is a marker of future cardiovascular morbidity and mortality among individuals with or without high resting BP or any other cardiovascular disease (CVD) signs and symptoms at present. The purpose of this study was to evaluate the association between SBP during submaximal exercise and cardiorespiratory fitness (CRF) among young men. Further, we investigated the trend displayed by submaximal SBP (SSBP) across different levels of CRF.

METHODS

Graded exercise test (GXT) using a Modified Bruce protocol was performed on 204 men; SSBP was recorded at each stage of the protocol. Quintiles of CRF were established on the basis of peak oxygen consumption (VO2), with the first quintile (Q) being the lowest fit group and fifth Q the most fit.

RESULTS

The mean VO2 peaks in Q 1 through 5 were 32.3, 39.1, 43.4, 48.1 and 55.5 ml/kg per min, respectively. In a model adjusted for age, race, body fat percentage, resting SBP, alcohol intake and smoking, the largest difference in SSBP was observed between men in Q 1 and 2, with 7.6 mmHg (P = 0.05), 9.4 mmHg (P = 0.02) and 9.5 mmHg (P = 0.04) lower SSBP at minutes 6, 8 and 10 of GXT, respectively. SSBP plateaus at Q 3, followed by an increase in the higher Qs, although still lower than Q1.

CONCLUSION

There was a reverse J-curve pattern relationship between SSBP and CRF, with the lowest SSBP among men with fair or good CRF and highest among those with poor CRF.

VIDEO ABSTRACT

http://links.lww.com/HJH/A538.

The Acute Risks of Exercise in Apparently Healthy Adults and Relevance for Prevention of Cardiovascular Events

BACKGROUND

Increased physical activity (PA) is associated with improved quality of life and reductions in cardiovascular (CV) morbidity and all-cause mortality in the general population in a dose-response manner. However, PA acutely increases the risk of adverse CV event or sudden cardiac death (SCD) above levels expected at rest. We review the likelihood of adverse CV events related to exercise in apparently healthy adults and strategies for prevention, and contextualize our understanding of the long-term risk reduction conferred from PA.

METHODS

A systematic review of the literature was performed using electronic databases; additional hand-picked relevant articles from reference lists and additional sources were included after the search.

RESULTS

The incidence of adverse CV events in adults is extremely low during and immediately after PA of varying types and intensities and is significantly lower in those with long-standing PA experience. The risk of SCD and nonfatal events during and immediately after PA remains extremely low (well below 0.01 per 10,000 participant hours); increasing age and PA intensity are associated with greater risk. In most cases of exercise-related SCD, occult CV disease is present and SCD is typically the first clinical event.

CONCLUSIONS

Exercise acutely increases the risk of adverse CV events, with greater risk associated with vigorous intensity. The risks of an adverse CV event during and immediately after exercise are outweighed by the health benefits of vigorous exercise performed regularly. A key challenge remains the identification of occult structural heart disease and inheritable conditions that increase the chances of lethal arrhythmias during exercise.

Use of Electrocardiogram as Part of the Preparticipation Examination

A sudden cardiac event or death in a young athlete is a traumatic and memorable event. These tragic events have long-lasting and widespread influences that not only affect the person's immediate family, but also have profound effects on the team, school, and entire community. Over the past several decades there has been a significant research effort in the area of sudden cardiac death (SCD) in athletes in hopes of decreasing preventable deaths. One area of research and discussion that has emerged is the use of electrocardiograms (EKGs) in preparticipation screening examinations as a tool to help identify athletes at risk for SCD. The use of an EKG in addition to a detailed history and physical examination is a controversial and frequently debated topic. To help sort through some of the controversy, this article discusses some of the pros and cons of incorporating the EKG as a screening modality in the preparticipation evaluation for clearance to participate in sports.

Benign and pathological electrocardiographic changes in athletes

Sudden cardiac death is the leading cause of death in athletes during sport. It is a tragic event that generates significant media attention and discussion throughout society as to whether everything possible had been done to prevent it. Regular physical exercise causes cardiac remodeling at both the mechanical and electrical level, known as athlete's heart, resulting in an electrocardiogram (ECG) considered abnormal compared with the ECGs of the general population. Some of these electrocardiographic changes are considered normal or physiological in athletes, while others suggest underlying cardiac disease with the potential to cause sudden cardiac death. There is thus an urgent need to define the electrocardiographic patterns that allow or prohibit participation in sports, and to differentiate them in terms of gender, ethnicity and age. The purpose of this review is to present the latest data on the electrocardiographic changes considered benign or pathological that are typically found in athletes and to critically analyze the most recent criteria for classifying ECGs in this population (the Seattle criteria), comparing them with previous guidelines and with the latest studies on the subject. This article also examines the question of including ECGs in pre-participation screening programs, the US and European approaches to the subject, and the most up-to-date data on the sensitivity, specificity and cost-effectiveness of the ECG in athletes.

National Athletic Trainers' Association position statement: Preparticipation physical examinations and disqualifying conditions

OBJECTIVE

To present athletic trainers with recommendations for the content and administration of the preparticipation physical examination (PPE) as well as considerations for determining safe participation in sports and identifying disqualifying conditions.

BACKGROUND

Preparticipation physical examinations have been used routinely for nearly 40 years. However, considerable debate exists as to their efficacy due to the lack of standardization in the process and the lack of conformity in the information that is gathered. With the continuing rise in sports participation at all levels and the growing number of reported cases of sudden death in organized athletics, the sports medicine community should consider adopting a standardized process for conducting the PPE to protect all parties.

RECOMMENDATIONS

Recommendations are provided to equip the sports medicine community with the tools necessary to conduct the PPE as effectively and efficiently as possible using available scientific evidence and best practices. In addition, the recommendations will help clinicians identify those conditions that may threaten the health and safety of participants in organized sports, may require further evaluation and intervention, or may result in potential disqualification.

Cardiovascular screening practices in collegiate student-athletes

OBJECTIVE

To evaluate screening practices and preparticipation evaluation (PPE) forms used to identify, or raise suspicion of, cardiovascular abnormalities in collegiate student-athletes.

DESIGN

Phone and e-mail survey.

SETTING

National Collegiate Athletic Association (NCAA) Division I universities.

PARTICIPANTS

All 347 NCAA Division I universities were invited to participate in 2010-2011; 257 universities (74%) elected to participate.

MAIN OUTCOME MEASURES

Information about the preparticipation screening process was obtained from team physicians and/or certified athletic trainers. PPE forms were evaluated for the inclusion of the 12 specific American Heart Association (AHA) recommendations for cardiovascular screening of competitive athletes from the 2007 AHA Council on Nutrition, Physical Activity, and Metabolism consensus panel endorsed by the American College of Cardiology Foundation.

RESULTS

All 257 participating universities (100%) required preparticipation screening for freshman and transfer athletes, and 83 universities (32%) required an annual PPE for returning athletes. The PPE was performed on campus at 85% of the universities, whereas 15% of universities allowed the PPE to be completed by the athlete's choice of physician before he or she arrived on campus. Eleven universities (4%) used the recently updated American College of Sports Medicine 4th edition PPE. Sixteen universities (6%) used the American College of Sports Medicine 3rd edition PPE. The remaining 260 universities (90%) did not use either of these forms. Of the 257 Division I universities, only 21 universities (8%) met the AHA recommendations by including all 12 cardiovascular screening items on their PPE forms.

CONCLUSION

The majority (92%) of NCAA Division I universities do not use PPE forms that meet the AHA recommendations for cardiovascular screening; therefore, they may not be effectively screening collegiate student-athletes for cardiovascular abnormalities that could lead to sudden cardiac death.

The ubiquitin proteasome system in human cardiomyopathies and heart failure

Maintenance of protein quality control is a critical function of the ubiquitin proteasome system (UPS). Evidence is rapidly mounting to link proteasome dysfunction with a multitude of cardiac diseases, including ischemia, reperfusion, atherosclerosis, hypertrophy, heart failure, and cardiomyopathies. Recent studies have demonstrated a remarkable level of complexity in the regulation of the UPS in the heart and suggest that our understanding of how UPS dysfunction might contribute to the pathophysiology of such a wide range of cardiac afflictions is still very limited. Whereas experimental systems, including animal models, are invaluable for exploring mechanisms and establishing pathogenicity of UPS dysfunction in cardiac disease, studies using human heart tissue provide a vital adjunct for establishing clinical relevance of experimental findings and promoting new hypotheses. Accordingly, this review will focus on UPS dysfunction in human dilated and hypertrophic cardiomyopathies and highlight areas rich for further study in this expanding field.

Formin homology 2 domain containing 3 variants associated with hypertrophic cardiomyopathy

BACKGROUND

Incomplete penetrance and variable expression of hypertrophic cardiomyopathy (HCM) is well appreciated. Common genetic polymorphisms variants that may affect HCM penetrance and expression have been predicted but are not well established.

METHODS AND RESULTS

We performed a case-control genomewide association study to identify common HCM-associated genetic polymorphisms and then asked whether such common variants were more represented in HCM or could explain the heterogeneity of HCM phenotypes. We identified an intronic FHOD3 variant (rs516514) associated with HCM (odds ratio, 2.45; 95% confidence interval, 1.76-3.41; P=1.25×10(-7)) and validated this finding in an independent cohort. Next, we tested FHOD3-V1151I (rs2303510), a nonsynonymous variant in partial linkage disequilibrium with rs516514, and we detected an even stronger association with HCM (P=1.76×10(-9)). Although HCM patients were more likely to carry these, FHOD3 allele subjects homozygous for FHOD3-1151I had similar HCM phenotypes as carriers of the V1151 allele. FHOD3 expression is increased in the setting of HCM, and both alleles of FHOD3-V1151I were detected in HCM myectomy tissue. Previously, FHOD3 was found to be required for formation of the sarcomere, and here we demonstrate that its fly homolog fhos is required for normal adult heart systolic contraction.

CONCLUSIONS

Here we demonstrate the association of a common nonsynonymous FHOD3 genetic variant with HCM. This discovery further strengthens the potential role of gene mutations and polymorphisms that alter the amino acid sequence of sarcomere proteins and HCM.

Sudden cardiac death in young athletes; a literature review and special considerations in Asia

Sudden cardiac death (SCD) in a young athlete is rare, but catastrophic. Exercise acts as a risk factor for SCD in people with cardiovascular disease. A diversity of cardiovascular disorders including hypertrophic cardiomyopathy, congenital coronary anomalies, arrhythmogenic right ventricular dysplasia, dilated cardiomyopathy, aortic rupture due to Marfan syndrome, myocarditis, valvular disease and electrical disorders (Wolff–Parkinson–White syndrome, long QT syndrome, Brugada syndrome), as well as commotio cordis represent the common causes of SCD in young athletes.

As the outcome of lethal cardiovascular disorders is not reversible except in few cases, effective measures should be addressed to reduce the burden of sudden cardiac death in young athletes. Currently, two types of recommendations are proposed by American and European countries.

It seems that there are some special considerations in Asia, entirely different from North America or Europe, which warrant more comprehensive research on epidemiology and etiology of SCD in young Asian athletes by country and evaluation of current national preventive strategies and their achievements in decreasing the risk. Using these data and considering regional restrictions, an expert group will be able to plan a practical and feasible preventive strategy.

Economic evaluation of strategies to reduce sudden cardiac death in young athletes

OBJECTIVE

There is controversy about appropriate methods to reduce sudden cardiac death (SCD) in young athletes, but there is limited evidence on costs or consequences of alternative strategies. The objective of this study was to evaluate the cost-effectiveness of adding electrocardiogram (ECG) screening to the currently standard practice of preparticipation history and physical examination (H&P) to reduce SCD.

METHODS

Decision analysis modeling by using a societal perspective, with annual Markov cycles from age 14 until death. Three screening strategies were evaluated: (1) H&P, with cardiology referral if abnormal (current standard practice); (2) H&P, plus ECG after negative H&P, and cardiology referral if either is abnormal; and (3) ECG only, with cardiology referral if abnormal. Children identified with SCD-associated cardiac abnormalities were restricted from sports and received cardiac treatment. Main outcome measures were costs of screening and treatment, quality-adjusted life years (QALYs), and premature deaths averted.

RESULTS

Relative to strategy 1, incremental cost-effectiveness is $68800/QALY for strategy 2 and $37700/QALY for strategy 3. Monte Carlo simulation revealed the chance of incremental cost-effectiveness compared with strategy 1 was 30% for strategy 2 and 66% for strategy 3 (assumed willingness to pay ≤$50000/QALY). Compared with strategy 1, strategy 2 averted 131 additional SCDs at $900000 per case, and strategy 3 averted 127 SCDs at $600000 per case.

CONCLUSIONS

Under a societal willingness to pay threshold of $50000/QALY, adding ECGs to current preparticipation evaluations for athletes is not cost-effective, with costs driven largely by false-positive findings.

Potential adverse cardiovascular effects from excessive endurance exercise

A routine of regular exercise is highly effective for prevention and treatment of many common chronic diseases and improves cardiovascular (CV) health and longevity. However, long-term excessive endurance exercise may induce pathologic structural remodeling of the heart and large arteries. Emerging data suggest that chronic training for and competing in extreme endurance events such as marathons, ultramarathons, ironman distance triathlons, and very long distance bicycle races, can cause transient acute volume overload of the atria and right ventricle, with transient reductions in right ventricular ejection fraction and elevations of cardiac biomarkers, all of which return to normal within 1 week. Over months to years of repetitive injury, this process, in some individuals, may lead to patchy myocardial fibrosis, particularly in the atria, interventricular septum, and right ventricle, creating a substrate for atrial and ventricular arrhythmias. Additionally, long-term excessive sustained exercise may be associated with coronary artery calcification, diastolic dysfunction, and large-artery wall stiffening. However, this concept is still hypothetical and there is some inconsistency in the reported findings. Furthermore, lifelong vigorous exercisers generally have low mortality rates and excellent functional capacity. Notwithstanding, the hypothesis that long-term excessive endurance exercise may induce adverse CV remodeling warrants further investigation to identify at-risk individuals and formulate physical fitness regimens for conferring optimal CV health and longevity.

Preparticipation athletic screening including an electrocardiogram: an unproven strategy for prevention of sudden cardiac death in the athlete

One of the fundamental principles of evidence-based medicine is that clinical practice should be based on evidence derived from sufficiently robust data to ensure that the benefits, risks, and costs of an intervention are known. Although intuitively appealing, athletic screening programs with routine electrocardiograms (ECGs) followed by restriction of at-risk individuals have not been demonstrated to be effective in decreasing the inherent risk of athletic sudden death. The incremental use of a screening ECG to a history and physical examination remains debatable because of insufficient evidence to conclusively resolve the issue. Long-term outcomes with a large group of athletes undergoing screening and restriction are limited to a small number of observational trials. One supports and many do not support ECG screening with athletic restriction of at-risk athletes. Although programs and policies to decrease sudden death are laudable, they need further evaluation before being implemented on a large-scale basis. Currently, athletes are best protected by a strategy of secondary prevention with improvements in resuscitation and emergency action plans.

March Madness 2011: for whom the bell tolls?

The American Heart Association has developed 12 recommendations for preparticipation screening of high school and college athletes, but the application of these recommendations across the US is inconsistent. A recent clinical study suggests that the incidence and prevalence of sudden athletic death (SAD) is greater than previously believed. Currently, diagnostic screening is considered too expensive and is delivered sporadically. Logic dictates that the medical community must become more involved in reducing the incidence and prevalence of SAD through an improved preparticipation screening process. An effective screening process must be able to reproducibly predict and prevent potential risk using the most effective resources and keeping the cost-benefit ratio at a minimum. The most effective use of our resources will limit the potential of liability for institutions and physicians and, hopefully, eliminate episodes of SAD.

Increased sympathetic activity can cause repolarization instability in athlete's heart

Sudden cardiac death (SCD) of athletes usually occurs during warm-up or shortly after training. At this point sympathetic tone is still elevated but oxygen demand does not differ from resting levels. It is supposed not to have a primarily ischemic origin but most likely relates to repolarization abnormalities which can be associated with intracellular cAMP level caused by increased sympathetic tone. The mediators of sympathetic nervous system are the catecholamines (epinephrin, norepinephrin). Measuring QT-dispersion can show the repolarization's inhomogeneity. 27 elite soccer players, 28 triathletes and 29 non-trained control person took part in our study. It was recorded cardiac ultrasound, an ECG and taken blood before and after exercise. We found significantly higher QT-dispersion and catecholamines in soccer players compared to the triathletes and the controls. However the soccer players did not show larger athlete's heart than the triathletes. After exercise the increased repolarization inhomogeneity persisted in soccer players, but in triathletes it decreased. Increased sympathetic tone in athletes can enhance arrhythmia propensity. Our data may explain why the soccer players die of sudden cardiac death most commonly in Europe.

Cardiac ventricular repolarization reserve: a principle for understanding drug-related proarrhythmic risk

Cardiac repolarization abnormalities can be caused by a wide range of cardiac and non-cardiac compounds and may lead to the development of life-threatening Torsades de Pointes (TdP) ventricular arrhythmias. Drug-induced torsades de pointes is associated with unexpected and unexplained sudden cardiac deaths resulting in the withdrawal of several compounds in the past. To better understand the mechanism of such unexpected sudden cardiac deaths, the concept of repolarization reserve has recently emerged. According to this concept, pharmacological, congenital or acquired impairment of one type of transmembrane ion channel does not necessarily result in excessive repolarization changes because other repolarizing currents can take over and compensate. In this review, the major factors contributing to repolarization reserve are discussed in the context of their clinical significance in physiological and pathophysiological conditions including drug administration, genetic defects, heart failure, diabetes mellitus, gender, renal failure, hypokalaemia, hypothyroidism and athletes' sudden deaths. In addition, pharmacological support of repolarization reserve as a possible therapeutic option is discussed. Some methods for the quantitative estimation of repolarization reserve are also recommended. It is concluded that repolarization reserve should be considered by safety pharmacologists to better understand, predict and prevent previously unexplained drug-induced sudden cardiac deaths.

Evidence-based risk assessment and recommendations for exercise testing and physical activity clearance in apparently healthy individuals1This paper is one of a selection of papers published in this Special Issue, entitled Evidence-based risk assessment and recommendations for physical activity clearance, and has undergone the Journal’s usual peer review process

Increased physical activity (PA) is associated with improved health and quality of life in the general population. A dose–response effect is evident between increasing levels of PA participation and a lower relative risk for cardiovascular disease and all-cause mortality. However, there is also clear evidence that PA acutely increases the risk of an adverse cardiovascular (CV) event and sudden cardiac death (SCD) significantly above levels expected at rest. Adverse CV events during PA may be triggered acutely by the physiological stress of exercise. This investigation will review the available literature describing the CV risks of exercise testing and PA participation in apparently healthy individuals. A systematic review of the literature was performed using electronic databases, including Medline, CINAHL, SPORT discus, EMBASE, Cochrane DSR, ACP Journal Club, and DARE; additional relevant articles were hand-picked and the final grouping was used for the review using the AGREE process to assess the impact and quality of the selected articles. Six hundred and sixteen relevant articles were reviewed with 51 being identified as describing adverse CV events during exercise and PA. Data suggests the risks of fatal and nonfatal events during maximal exercise testing in apparently healthy individuals rarely occur (approximately <0.8 per 10 000 tests or 1 per 10 000 h of testing). The incidence of adverse CV events is extremely low during PA of varying types and intensities, with data limited almost exclusively to fatal CV events, as nonfatal events are rarely reported. However, this risk is reduced by 25%–50% in those individuals who have prior experience with increased levels of PA, particularly vigorous PA. Throughout a wide age range, the risk of SCD and nonfatal events during PA remain extremely low (well below 0.01 per 10 000 participant hours), but both increasing age and PA intensity are associated with greater risk. In most cases of exercise-related SCD, undetected pre-existing disease is present and SCD is typically the first clinical event. The risks of an adverse CV event during exercise testing and PA are rare and are outweighed by the health benefits. Given this risk-benefit relationship, the PAR-Q is an appropriate method to identify those at higher risk across a wide age span and should be used in conjunction with appropriate clinical guidelines for guiding individuals towards graduated PA. There are not adequate data to describe the risks of PA in those individuals considered to be at higher risk but without cardiovascular disease.

Incidence of sudden cardiac death in National Collegiate Athletic Association athletes

BACKGROUND

The true incidence of sudden cardiac death (SCD) in US athletes is unknown. Current estimates are based largely on case identification through public media reports and estimated participation rates. The purpose of this study was to more precisely estimate the incidence of SCD in National Collegiate Athletic Association (NCAA) student-athletes and assess the accuracy of traditional methods for collecting data on SCD.

METHODS AND RESULTS

From January 2004 through December 2008, all cases of sudden death in NCAA student-athletes were identified by use of an NCAA database, weekly systematic search of public media reports, and catastrophic insurance claims. During the 5-year period, there were 273 deaths and a total of 1 969 663 athlete participant-years. Of these 273 deaths, 187 (68%) were due to nonmedical or traumatic causes, 80 (29%) to medical causes, and 6 (2%) to unknown causes. Cardiovascular-related sudden death was the leading cause of death in 45 (56%) of 80 medical cases, and represented 75% of sudden deaths during exertion. The incidence of SCD was 1:43 770 participants per year. Among NCAA Division I male basketball players, the rate of SCD was 1:3100 per year. Thirty-nine (87%) of the 45 cardiac cases were identified in the NCAA database, only 25 (56%) by use of public media reports, and 9 (20%) from catastrophic claims data.

CONCLUSIONS

SCD is the leading medical cause of death and death during exercise in NCAA student-athletes. Current methods of data collection underestimate the risk of SCD. Accurate assessment of SCD incidence is necessary to shape appropriate health policy decisions and develop effective strategies for prevention.

Strategies for the prevention and treatment of sudden cardiac death

Cardiovascular diseases account for 40% of all deaths in the West. Sudden cardiac death (SCD) is a major health problem affecting over 300,000 patients annually in the United States alone. Presence of coronary artery disease (CAD), usually in the setting of diminished left ventricular ejection fraction, is still the single major risk factor for SCD. Additionally, acute myocardial ischemia, structural cardiac defects, anomalous coronary arteries, cardiomyopathies, genetic mutations, and ventricular arrhythmias are all attributed to SCD, demonstrating the perplexity of this condition. With the recent advancements in cardiovascular medicine, the incidence of SCD is expected to increase steeply as the prevalence of CAD and heart failure is uprising in general population. Considering SCD, the major challenge confronting contemporary cardiology, multiple strategies for prevention against SCD have been developed. β-blockers have been shown to reduce the risk of SCD, whereas implantable cardioverter-defibrillator devices are found to be effective at terminating the malignant arrhythmias. In recent years, multiple clinical trials were carried out to identify patients who may benefit from preventive intervention, including medical therapy and automatic cardioverter-defibrillator implantations. This review article provides insight into the advanced strategies for the prevention and treatment of SCD based on the data available in medical literature to date.

Organic fitness: physical activity consistent with our hunter-gatherer heritage

Many of the pervasive health concerns in modern society are the result of diet and lifestyle choices that are at odds with the evolutionary milieu for which we remain genetically adapted. This systematic displacement from a very physically active lifestyle in a natural outdoor environment to a sedentary indoor lifestyle may be at the root of many chronic diseases that are endemic in our culture. A proposed solution is to simulate indigenous human activity patterns in a way that is possible and practical for individuals to achieve. Suggestions for exercise mode, duration, intensity, and frequency are outlined, with a focus on realigning our daily physical activities with the archetype that is encoded within our genome. In a sedentary individual, this type of daily physical activity should help confer the robust vigorous health that enabled our ancestors to survive and thrive as hunter-gatherers in the wild.

Strong cross-bridges potentiate the Ca(2+) affinity changes produced by hypertrophic cardiomyopathy cardiac troponin C mutants in myofilaments: a fast kinetic approach

This spectroscopic study examined the steady-state and kinetic parameters governing the cross-bridge effect on the increased Ca(2+) affinity of hypertrophic cardiomyopathy-cardiac troponin C (HCM-cTnC) mutants. Previously, we found that incorporation of the A8V and D145E HCM-cTnC mutants, but not E134D into thin filaments (TFs), increased the apparent Ca(2+) affinity relative to TFs containing the WT protein. Here, we show that the addition of myosin subfragment 1 (S1) to TFs reconstituted with these mutants in the absence of MgATP(2-), the condition conducive to rigor cross-bridge formation, further increased the apparent Ca(2+) affinity. Stopped-flow fluorescence techniques were used to determine the kinetics of Ca(2+) dissociation (k(off)) from the cTnC mutants in the presence of TFs and S1. At a high level of complexity (i.e. TF + S1), an increase in the Ca(2+) affinity and decrease in k(off) was achieved for the A8V and D145E mutants when compared with WT. Therefore, it appears that the cTnC Ca(2+) off-rate is most likely to be affected rather than the Ca(2+) on rate. At all levels of TF complexity, the results obtained with the E134D mutant reproduced those seen with the WT protein. We conclude that strong cross-bridges potentiate the Ca(2+)-sensitizing effect of HCM-cTnC mutants on the myofilament. Finally, the slower k(off) from the A8V and D145E mutants can be directly correlated with the diastolic dysfunction seen in these patients.

Electrocardiogram testing during athletic preparticipation physical examinations

CONTEXT

Sudden cardiac death (SCD) is a relatively rare yet unfortunate risk of athletic participation. To reduce the incidence of SCD, electrocardiogram (ECG) use during athletic preparticipation examinations (PPEs) has been proposed to detect underlying cardiac abnormalities.

OBJECTIVE

To estimate the effectiveness of ECG use during athletic PPEs.

DESIGN

Epidemiologic modeling.

POPULATIONS

Public high school athletes.

DATA COLLECTION AND ANALYSIS

Estimates of ECG sensitivity (70%) and specificity (84%) were drawn from the literature, as was the estimate of overall prevalence of cardiac conditions relevant to SCD (0.3%). Participation rate by sex was determined from National Federation of State High School Associations data. Participation by ethnicity was assumed to be proportionate to the public high school attendance rates for grades 9 through 12 (18.4% African American). Population-specific ECG effectiveness (positive predictive value), estimated total costs, cost per year of life saved, and cost to identify 1 additional case were computed. Total annual PPE screening costs reflected a cardiologist's office visit, including echocardiogram for those athletes with a positive ECG screen.

RESULTS

The model predicted that 16% of all athletes would be expected to have a positive ECG, but only 1.3% of athletes with a positive ECG would have a cardiac abnormality capable of causing SCD, including hypertrophic cardiomyopathy, structural defects, and various conduction abnormalities. Total annual cost estimates for ECG screening and follow-up exceeded $126 million. Average cost per year of life saved across groups was $2693, and the cost to identify 1 additional case averaged $100 827. Compared with females, males had both lower cost per year of life saved and lower cost to identify 1 true case. Similarly, black males exhibited lower costs than white males. Across groups, false-positive ECG screening exams accounted for 98.8% of follow-up costs.

CONCLUSIONS

Large-scale, mass ECG testing would be a costly method to identify athletes with cardiac abnormalities. Targeting high-risk populations can increase the effectiveness of the ECG for athletic PPE screening.

Cost-effectiveness of preparticipation screening for prevention of sudden cardiac death in young athletes

BACKGROUND

Inclusion of 12-lead electrocardiography (ECG) in preparticipation screening of young athletes is controversial because of concerns about cost-effectiveness.

OBJECTIVE

To evaluate the cost-effectiveness of ECG plus cardiovascular-focused history and physical examination compared with cardiovascular-focused history and physical examination alone for preparticipation screening.

DESIGN

Decision-analysis, cost-effectiveness model.

DATA SOURCES

Published epidemiologic and preparticipation screening data, vital statistics, and other publicly available data.

TARGET POPULATION

Competitive athletes in high school and college aged 14 to 22 years.

TIME HORIZON

Lifetime.

PERSPECTIVE

Societal.

INTERVENTION

Nonparticipation in competitive athletic activity and disease-specific treatment for identified athletes with heart disease.

OUTCOME MEASURE

Incremental health care cost per life-year gained.

RESULTS OF BASE-CASE ANALYSIS

Addition of ECG to preparticipation screening saves 2.06 life-years per 1000 athletes at an incremental total cost of $89 per athlete and yields a cost-effectiveness ratio of $42 900 per life-year saved (95% CI, $21 200 to $71 300 per life-year saved) compared with cardiovascular-focused history and physical examination alone. Compared with no screening, ECG plus cardiovascular-focused history and physical examination saves 2.6 life-years per 1000 athletes screened and costs $199 per athlete, yielding a cost-effectiveness ratio of $76 100 per life-year saved ($62 400 to $130 000).

RESULTS OF SENSITIVITY ANALYSIS

Results are sensitive to the relative risk reduction associated with nonparticipation and the cost of initial screening.

LIMITATIONS

Effectiveness data are derived from 1 major European study. Patterns of causes of sudden death may vary among countries.

CONCLUSION

Screening young athletes with 12-lead ECG plus cardiovascular-focused history and physical examination may be cost-effective.

PRIMARY FUNDING SOURCE

Stanford Cardiovascular Institute and the Breetwor Foundation.

Possible mechanisms of sudden cardiac death in top athletes: a basic cardiac electrophysiological point of view

Sudden death among athletes is very rare (1:50,000-1:100,000 annually) but it is still 2-4 times more frequent than in the age-matched control population and attracts significant media attention. We propose a mechanism underlying sudden cardiac death in athletes that does not relate to myocardial ischemia but is based on repolarization abnormalities due to potassium channel downregulation and can also be best explained by the concurrent presence of several factors such as cardiac hypertrophy (athlete's heart), and/or hypertrophic cardiomyopathy, increased sympathetic tone, genetic defects, drugs, doping agents, food, or dietary ingredients. These factors together can increase the repolarization inhomogeneity of the heart ("substrate") and an otherwise harmless extrasystole ("trigger") occurring with a very unfortunate timing may sometimes induce life-threatening arrhythmias. The effective and possible prevention of sudden cardiac death requires the development of novel cost effective cardiac electrophysiological screening methods. Athletes identified by these tests as individuals at higher proarrhythmic risk should then be subjected to more costly genetic tests in order to uncover possible underlying genetic causes for alterations in ionic channel structure and/or function.

Dramatic electrocardiographic changes in a junior athlete with unpredictable hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is one of the commonest causes of sudden cardiac death in young athletes. Over the last years, the Italian preparticipation screening programme strongly contributed to discriminate athletes showing borderline (grey-area) left ventricular hypertrophy or fulfilling precise diagnostic criteria for HCM, thanks to the framework of testing performed yearly before competitions. We present the case of a junior athlete in whom dramatic ECG changes suggestive for HCM became manifest during the last year training activity.

Athletes at Risk for Sudden Cardiac Death

High school athletes represent the largest group of individuals affected by sudden cardiac death, with an estimated incidence of once or twice per week. Structural cardiovascular abnormalities are the most frequent cause of sudden cardiac death. Athletes participating in basketball, football, track, soccer, baseball, and swimming were found to have the highest incidence of sudden cardiac death. Screening of athletes prior to participation in competitive sports usually falls short of recommended guidelines. Poorly defined legislation and the absence of a national standard for sports physicals have contributed to inadequate health screenings of athletes. This article will describe the incidence and causes of sudden cardiovascular death in young athletes as well as guidelines intended to prevent this unfortunate problem.

Penetrance and risk profile in inherited cardiac diseases studied in a dedicated screening clinic

Genetically transmitted cardiomyopathies can affect several members in a family. Identification of high-risk patients could lead to a preventive treatment. We report the results of a 5-year experience of a dedicated clinic. Family screening was offered to 493 consecutive unrelated patients; 2,328 subjects (40 +/- 19 years old, 52% men) were evaluated (mean 4.4 relatives/family). Electrocardiography and echocardiography were performed in all cases; additional tests were indicated depending on the disease. Familial study was recommended because of a proband with hypertrophic cardiomyopathy (HC) in 57%, idiopathic dilated cardiomyopathy (IDC) in 14%, arrhythmogenic right ventricular cardiomyopathy (ARVC) in 2%, left ventricular noncompaction in 2%, Brugada syndrome (BS) in 15%, long QT syndrome (LQTS) in 3%, and other conditions in 6%. Familial disease was confirmed in 164 (39%); 43% with HC, 47% with IDC, 25% with ARVC, 33% with left ventricular noncompaction, 28% with BS, and 30% with LQTS. Two hundred twenty-two (44 +/- 20 years old, 60% men) affected relatives were identified (129 of whom were newly diagnosed). Sixty-four patients were newly diagnosed with HC, 40 with IDC, 2 with ARVC, 5 with left ventricular noncompaction, 14 with BS, and 2 with LQTS, in whom appropriate risk stratification and medication, if needed, were initiated (specific medication in 40, 31.0%). Cardioverter-defibrillator implantation was indicated in 4 relatives for primary prevention. Ninety-two (18.7%) had a family history of sudden death (FHSCD). Consanguinity was rare but significantly associated to a higher percentage of family disease (75.0% vs 38.3%, p = 0.003) and family history of sudden death (42.1% vs 17.8, p <0.001). In conclusion, the prevalence of familial disease in inherited cardiac conditions is high. Systematic familial study identified many asymptomatic affected patients who could benefit from early treatment to prevent complications. Dedicated clinics and multidisciplinary teams are needed for proper screening programs.