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Despite numerous studies published over the past decades, ambiguity still exists on both the absolute prevalence of sudden cardiac death among competitive athletes and the optimal strategy to prevent such tragic events.
In this impressive study (1), the authors now meticulously analyzed the results of a systematic screening program in adolescent, pre-professional soccer players in the United Kingdom, initiated in 1996 and endorsed by the English Football Association. By systematically applying a health questionnaire, physical examination, 12-lead ECG and echocardiography to 11,168 athletes, they detected 42 athletes with cardiac disorders associated with sudden cardiac death (SCD). Of these, two had finally died from known hypertrophic cardiomyopathy after having continued exercise against medical advice. Interestingly, among those athletes with negative initial screening results (10,338) or those having undergone further evaluation without pathological findings (287), 21 athletes died during follow-up, with 6 deaths being attributable to cardiac disease; other causes included cancer, road traffic accidents, drug overdose and suicide. Overall, 8 out of 23 deaths were attributable to cardiac causes, all of which were sudden and occurred during exercise. The overall prevalence of SCD was 6.8 deaths per 100,000 athletes.
Strengths of this study include the long observation period (1996-2016) with detailed recording of SCD events and causes including autopsy reports, the large uniform cohort undergoing a systematic uniform screening protocol, and the blinded validation of screening results of athletes having died despite showing negative screening results.
In contrast, findings are limited by evaluating only adolescent, almost exclusively male (95%) soccer players in an age group (16.4±1.2 years) where physiological or pathological cardiac alterations may not yet be detectable. Upper limits of cardiac dimensions from adult populations were applied that might not readily be transferable to younger athletes (e.g. LVEDD > 59 mm), resulting in a potential diagnostic bias. SCD events were partly reported on a voluntary basis, exercise testing was not routinely applied, and it is not reported how many athletes had pursued a professional career during follow-up or had quit playing soccer regularly.
Surprisingly, more athletes with negative than positive test results (6 vs. 2) died from cardiac causes, questioning the value of routine screening. One athlete appeared to have died only 1-2 months after screening, with a diagnosis of idiopathic left ventricular hypertrophy; this should usually have been detectable at least by echocardiography. On the other hand, another athlete died 7 years after screening from dilated cardiomyopathy, indicating that screening on a more regular basis (e.g. annually) would perhaps have saved his life. With respect to the “ECG debate”, almost all (86%) athletes detected with cardiac disorders associated with SCD showed an abnormal ECG, whereas only 4 (9%) had symptoms or abnormalities during physical examination – a finding that clearly supports the implementation of an ECG in a routine screening program.
Moreover, borderline findings in ECG and echocardiography contributed substantially to the initiation of further investigations including MRI. In contrast, 2% of athletes with such findings did not develop cardiac disease during follow-up, supporting the theory of false-positive results leading to unnecessary further examinations.
Despite higher costs it might therefore have been of value to also include routine exercise testing in the screening program. Although this cannot be derived from the data presented, some of the athletes with negative findings might have become apparent when performing a maximal exercise test, e.g. by showing arrhythmias, since this does simply reflect what athletes do on a daily basis – exercise.
Apart from the main findings of the study, some interesting information is provided referring to issues that do still not represent common consensus among experts: Return-to-play was obviously possible without complications in athletes undergoing surgical correction of coronary artery anomalies, septal defects or aortic root dilatation, and ablation of accessory pathways was performed in 24 of 26 athletes with accidental findings of a WPW pattern, enabling safe continued sports participation as well.
And there is another issue: it´s not only about preventing SCD in young athletes. Avoiding road traffic accidents may hardly be possible, but paying additional attention to risk factors for cancer or, in particular, suicidal tendencies represent other important parts of medical evaluation, and drug abuse in young athletes participating in organized sports should alarm the authorities anyway.
In conclusion, the study revealed a relatively high rate of SCD among male adolescent soccer players. The vast majority of abnormalities associated with an increased SCD risk were detected by ECG and echocardiography, confirming the value of these techniques as part of pre-participation screening. We should, however, be aware of a substantially higher number of athletes at risk, requiring extended or repeated screening programs, since disorders may become apparent only at older ages. And remember - all athletes with SCD died during exercise! We can learn a lot from this study, but once again: more research on timing, content and outcomes of screening is still required.
Note: The content of this article reflects the personal opinion of the author and is not necessarily the official position of the European Society of Cardiology.
Axel Pressler commented on this article:
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