Sudden cardiac death and preparticipation screening: the debate continues-in support of electrocardiogram-inclusive preparticipation screening

Sudden cardiac death (SCD) is the leading cause of death in young athletes during exercise, and there is international agreement among major medical and sporting bodies that young athletes should undergo preparticipation cardiovascular screening. However, there is currently no universally accepted screening protocol, and substantial debate exists about what constitutes the ideal approach to preparticipation screening. The primary objective of preparticipation screening is the detection of intrinsic structural or electrical cardiovascular disorders that predispose an athlete to SCD. Considerable evidence exists suggesting that screening athletes with only a history and physical examination leaves most athletes with a serious underlying cardiovascular disease undetected and, thus, cannot adequately achieve the primary objective of screening. Preparticipating cardiovascular screening inclusive of an electrocardiogram (ECG) greatly enhances the ability to identify athletes at risk and is the only model shown to be cost-effective and may reduce the rate of SCD. The major obstacle to ECG screening in the United States is the lack of a physician workforce skilled in interpretation of an athlete's ECG. However, recent studies have demonstrated a capacity to distinguish physiologic ECG alterations in athletes from findings suggestive of underlying pathology that is both feasible and has a low false-positive rate. Efforts are underway to increase physician education in ECG interpretation. After 2 decades debating the proper screening strategy to identify athletes at risk, the weight of scientific evidence suggests that a screening program inclusive of ECG is the only strategy that merits promotion.     

The athlete's heart syndrome

The athlete's heart is a benign condition, associated with physiologic alterations that can be detected on physical and laboratory examination. Echocardiography is a particularly useful technique is quantitating cardiac adaptation to exercise training and in screening for cardiovascular disorders that can be deleterious to the athlete. Cardiomyopathies are common causes of sudden death in young athletes, and myocarditis in physically-active young military recruits. Coronary disease is usually implicated in middle-aged athletes such as distance runners. Recent well-publicized deaths in several athletes have focused more attention on the need to detect Marfan's syndrome and cocaine use. Published guidelines such as the 16th Bethesda Conference and recent medical advances like new antihypertensive and antiarrhythmic drugs assist the clinician in counseling and managing athletes with cardiovascular disorders.     

Diagnostic accuracy of extended-length electrocardiogram in differentiating between athlete's heart and hypertrophic cardiomyopathy

Background

Standard 12-lead electrocardiogram (ECG) has several limitations in solving the differential diagnosis between physiologic left ventricular hypertrophy (PLVH) and hypertrophic cardiomyopathy (HCM), given the high rate of false-positive results in athletes. The aim of this study was to assess the usefulness of several arrhythmic risk indexes in differentiating PLVH from HCM.

Methods

A multiparametric ECG analysis (extended-length ECG) was performed on 30 male athletes with PLVH and 30 male patients with HCM, with homogeneous age distribution.

Results

The combination of 4 extended-length ECG variables, namely, corrected QT interval (Bazett), QT dispersion, mean resting heart rate, and low-amplitude signal duration at 25 Hz (low-amplitude signal duration at the end of filtered QRS) displayed remarkable diagnostic accuracy (area under receiver operating characteristic curve, 94%). The same accuracy was obtained replacing QT dispersion with T-wave complexity index.

Conclusions

Extended-length ECG can be considered an effective, low-cost, and low time-consuming clinical tool for distinguishing between PLVH and HCM.     

The athlete's heart. Historical perspectives.

Even an athlete's heart may be affected by clinical conditions. Regarding the extreme performances of the athlete's heart in training and competition, even conditions that might be harmless in sedentary people can be fatal for the athlete. Looking back on the history of the athlete's heart, some common mistakes in its assessment can be avoided that might harm the athlete on the misinterpretation of adaptational phenomena or the trivialization of clinical conditions.     

The preparticipation sports examination. Cardiovascular considerations for screening.

Physicians performing cardiovascular screening examinations in young and adult athletes should be aware of the rarity of exercise complications and the difficulty in separating cardiac adaptations to training from pathologic conditions. Coronary artery disease is the predominant cause of cardiac events during exercise in adults, whereas congenital abnormalities are the primary cause of exercise deaths in children. The preparticipation cardiac examination should include blood pressure measurements, visual inspection for the Marfan habitus, and auscultation designed to detect ventricular outflow obstruction. Other cardiovascular testing should be used when symptoms or findings warrant further evaluation.     

Sudden death and the competitive athlete: perspectives on preparticipation screening studies

Sudden death in healthy athletes is uncommon but, when it occurs, the primary mechanism is cardiovascular. The major cause of sudden death in the young athlete is hypertrophic cardiomyopathy or related conditions characterized by left ventricular hypertrophy, aortic rupture due to cystic medial necrosis and congenital coronary artery abnormalities. In the middle-aged or older athlete, coronary artery disease is the most significant cause of sudden death. Noninvasive screening procedures are currently available that can detect most subjects at risk of sudden death. However, although some potentially lethal diseases can be excluded by a relatively simple screening program, other diseases require expensive procedures, such as echocardiography and exercise electrocardiographic stress testing. This means that the sensitivity of detecting diseases leading to sudden death increases in proportion to the financial resources that can be applied to the screening program. Thus, when a screening program designed to identify all cardiac diseases that have the potential to cause sudden death is planned by a community, school or nonprofessional athletic team, the costs will almost undoubtedly be considered prohibitive. The practicality of applying a community- or school-initiated screening program can be questioned because of the very low incidence of sudden unexpected death in young healthy individuals. It is therefore likely that comprehensive screening programs will be confined to individuals or organizations with adequate financial resources. Less expensive, limited screening can be undertaken by individuals or groups to identify some subjects at risk of sudden death during athletic competition.     

Ventricular arrhythmias and athlete's heart: Role of signal-averaged electrocardiography

The aim of this study was to assess the prevalence and the prognosticvalue of ventricular late potentials in apparently healthy top-levelathletes with ventricular arrhythmias, and the effect of physiologicalmyocardial hypertrophy (athlete's heart) on the electrogenesisof the signal-averaged electrocardiogram (ECG). Two groups ofasymptomatic athletes without underlying heart disease werestudied: group A consisted of 35 athletes without arrhythmiasand group B of 25 athletes with frequent and complex ventricular arrhythmias (ventricular ectopic beats >5000. 24 h^–1and ventricular couplets >15 . 24 h^–1). Late potentialswere present if athletes had significantly prolonged filteredQRS and low amplitude signal duration and low root mean squarevoltages at both 25–250 Hz and 40–250 Hz filters.While late potentials were absent in all normal athletes ofgroup A, they were present in seven of 25 (28%) athletes witharrhythmias of group B (P<0·003 Ten of 25 athletes(five with and five without late potentials) of group B underwentprogrammed ventricular stimulation using a protocol comprisingup to three extrastimuli. No episode of sustained ventriculartachycardia was induced. In four of five athletes with latepotentials and in one of five without them, unsustained ventricularresponses were induced. Echocardiographically determined leftventricular mass found in both groups of athletes did not influencethe pathological result of the signal-averaged ECG parameters. This study shows the applicability of the signal-averaged ECGin identifying ventricular late potentials in a selected populationof top-level athletes with frequent and complex ventriculararrhythmias and without overt heart disease; it also shows thatthe presence of late potentials is not influenced by left ventricularmass, even if extreme (>350 g), and it is correlated to anon-sustained ventricular response during an electrophysiologicalstudy.     

The electrocardiogram in luetic,arteriosclerotic, and rheumatic heart disease

As a result of this study of one hundred cases of advanced cardiovascular lues, using like numbers of cases of arteriosclerotic and rheumatic heart disease for comparison, it seems quite evident that there are no electrocardiographic findings pathognomonic of luetic heart disease.The electrocardiographic picture in luetic and arteriosclerotic disease shows a striking parallelism. The variations from the normal as found are due to the myocardial degeneration, and are not characteristic of the lues per se. While it is true that certain of the arrhythmias and certain abnormalities of the T-wave are of sinister prognostic import, it appears to be quite true that this is the case in the arteriosclerotic as well as in the luetic cases. There is thus no characteristic electrocardiographic picture of cardiovascular lues, and it is not justifiable to make definite forecasts of the prognosis in this disease from the electrocardiogram alone.     

Hypertrophic cardiomyopathy and athlete's heart: a tale of two entities

Sudden death during sports activities, although unfrequent,is a tragic event with great impact on both the general andmedical communities. The two commonest conditions leading tosudden cardiac death in young athletes are hyperthrophic cardiomyopathy(HCM), the main cause in the USA, and arrythmogenic right ventricularcardiomyopathy, which is the leading cause in Europe. We report the case of a 17-year-old football player with a pathologicalelectrocardiography (ECG) in the pre-participation screeningprogramme, highly suggestive of HCM, in which ECG study showeda septum thickness of 28 mm. Genetic analysis revealed R 495W mutation in the 18 exon of the MyBPC3 (myosin-binding proteinC) and sports activities were contraindicated. Two years later,septum thickness was 19.5 mm. Usefulness of 12-lead ECG, differentialdiagnosis between athlete's heart and HCM, and the stratificationin patients with HCM are discussed.     

The vectorcardiogram pattern of the athlete's heart (author's transl)

In order to assess the vectorcardiographic pattern of the athlete's heart, we evaluated the vectorcardiograms of 17 professional footballers; the signs of ventricular hypertrophy were particularly studied. 9 athletes had left ventricular hypertrophy, 3 showed VCgraphic signs of combined ventricular hypertrophy and 5 had normal vectorcardiograms. In all athletes with left ventricular hypertrophy the initial forces had normal spatial orientation (I A left ventricular hypertrophy). Likely, the combined right ventricular hypertrophy explains these VCgraphic patterns. The QRS loop did not show abnormal morphology, only the high magnitude of the spatial maximum QRS vectors was significant for diagnosis of left ventricular hypertrophy. The increase of the cardiac volumes induced by training might explain the high magnitude of the QRS loop.