Sudden death in athletes, even if it is a rare event, always has a negative impact on the population and medical community, because occurs at young individuals, apparently healthy and because of intense media coverage.
For a long time it was assumed that sudden death is caused by myocardial infarction even though there was no evidence to support this hypothesis. Now we know that arrhythmia is the most common mechanism (malignant ventricular arrhythmias), that occurs in congenital or acquired diseases that were or could not be diagnosed in time. Lately, implementation of screening programs for cardiovascular diseases before engaging in an intense sporting activity, increased the number of individuals with identified anomalies that are at increased risk of sudden death, excluding them from competitive sport.
Required elements for screening are as recommended by AHA (American Heart Association): medical history and physical examination.
The medical history should include personal history data (ie presence of discomfort/pain on exertion, unexplained faintness /syncope, occurred especially during effort, fatigue / dyspnea accented on exertion, heart murmurs mentioned in history, elevated blood pressure values) and family history (premature death under the age of 50 by cardiac cause, heart disease in close relatives under 50 years, relatives with known diseases at risk of sudden death: hypertrophic cardiomyopathy, dilated cardiomyopathy, long QT syndrome or other channelopathies, Marfan syndrome, severe arrhythmias).
Physical examination should be oriented to detect heart murmurs (examination in both supine and standing positions or during Valsalva maneuver, usually to identify murmurs due to dynamic left ventricle outflow tract obstruction), evaluation of femoral pulses to exclude coarctation of the aorta, physical stigmata of Marfan syndrome, measurement of BP in sitting position on both arms.
There is still controversy regarding the mandatory inclusion of ECG examination in the screening program. It is recommended by the European Society of Cardiology and not recommended by American Society, being considered not cost-effective. Sudden death that occurs during intense and sustained effort is most often the first manifestation of a cardiovascular disease. Most athletes who die have no family history and no symptoms or signs of cardiovascular disease. Therefore, screening program based solely on history and physical examination has limited value in detecting individuals with an underlying disease and preventing deaths. Adding noninvasive assessments, especially ECG increases sensitivity of screening process, this being shown in Italy in the last 25-30 years when at ECG evaluation were detected and disqualified from competition athletes with hypertrophic cardiomyopathy or other cardiomyopathies, decreasing significantly the annual incidence of sudden death (approx. 90%).
ECG changes that occur frequently as a result of training are sinus bradycardia, first degree atrioventricular block, minor right bundle branch block, early repolarization, singular presence of QRS voltage criteria for left ventricular hypertrophy. In the absence of other suggestive elements, these are physiological changes and should not be prohibited or discouraged the athletic activity and don’t requires a further investigation.
Non-exercise ECG changes are: presence of negative T waves, ST segment depression, pathological Q waves, left atrial enlargement, left axis deviation/left anterior hemiblock, right axis deviation /posterior left hemiblock, right ventricular hypertrophy, ventricular pre-excitation, left or right block, long or short QT, Brugada type of early repolarization. Any of these changes require additional noninvasive or invasive investigations, as appropriate (echocardiogram, stress test, angiography, MRI, CT, electrophysiological study, myocardial biopsy, etc.).
The incidence of sudden death is estimated at 0.5-2/100 000 per year. Distribution of causes of sudden death is 36% hypertrophic cardiomyopathy, 17% coronary artery anomalies, myocarditis 6%, right ventricle arrhythmogenic dysplasia 4%, 4% – mitral valve prolapse, anterior descending artery intramyocardial paths 3%, 3% coronary artery disease, aortic stenosis 3%, 2% dilated cardiomyopathy, sarcoidosis 1%, 2% aortic rupture, channelopathies 3%, other congenital heart diseases 2%, other causes 3%, 3% normal heart.
Although most deaths occurred at basketball and football players, it has not been demonstrated a link between the type of sport and the risk of cardiovascular events.
At athletes aged over 35 years the most common cause of sudden death is coronary artery disease, postmortem evaluations showing diffuse atherosclerotic disease with significant stenoses in two or more coronary trunks, where acute thrombosis overlapped. Mechanisms of cardiac arrest are: malignant arrhythmic events: ventricular tachycardia /ventricular fibrillation on myocardial scarring, acute myocardial ischemia, or both, electrical instability is favored by sympathetic stimulation during exercise. In younger athletes with premature coronary lesion, usually a single-vessel is affected like proximal left anterior descending artery in the absence of acute thrombosis, probably associated with increased vasoreactivity (coronary spasm). Since stress testing has significant limitations for the detection of these lesions (myocardial infarction and sudden death can occur even in a negative stress test), identification of patients at risk remains a challenge.
This is by far the most common cause of sudden death in athletes. Is predominantly genetically transmitted disease, characterized by muscle hypertrophy without dilatation of the left ventricle in the absence of other causes that lead to these changes. Generally, it is found a disproportionate hypertrophy of the interventricular septum, left ventricle cavity reduction with increased myocardial rigidity and impaired diastolic dysfunction affecting intramural coronary filling. In many patients, it is found a dynamic outflow obstruction of left ventricle, more pronounced during exercise and can cause syncope. Cardiac arrest is due to malignant ventricular arrhythmias occurring on a substrate of myocardial electrical instability due to myocytes disruption and diffuse fibrosis plus ischemia during exercise due to poor coronary filling.
Arrhythmogenic right ventricular dysplasia
It is another disease with genetic determinism, predominantly with autosomal dominant transmission characterized by fibro-adipose replacement of ventricular myocardium, determining right ventricle dilation and dysfunction with the appearance of areas with aneurysmal dilatation, areas that are potential sources for malignant ventricular arrhythmias. Sudden death during exercise is due to hemodynamic and neurohumoral factors causing increased afterload and cavitary dilation triggering arrhythmias.
Congenital coronary anomalies with risk for sudden death are the anomalous origin of the coronary arteries in other areas than normal sinus. It is assumed that death occurs due to expansion of the aortic root at effort that compresses the coronary artery into the pulmonary artery, causing myocardial ischemia. It is very difficult to diagnose this without specific examination (angiography, CT angiography).
Substrate for sudden death due to myocarditis is inflammation or fibrous process that can trigger arrhythmias.
If aorta is ruptured/dissected in pericardium, the tamponade causes electromechanical dissociation. It can be met isolated, but most frequently in association with coarctation of the aorta, bicuspid aorta, Marfan syndrome.
In mitral valve prolapse the pathogenesis of sudden death remains unknown. Have been proposed as possible mechanisms: coronary embolism or malignant tachyarrhythmias due to mechanical damage caused by prolapsed valve.
In approximately 2-5% of patients with sudden death it can not be highlighted a structural cause, death being due to primary electrical heart diseases, so-called channelopathies, inherited ion channel defects, causing malignant tachyarrhythmias: long QT syndrome, Brugada syndrome and catecholaminergic polymorphic ventricular tachycardia.
Two circumstances are related to sudden cardiac death on normal heart: strong neck trauma (causing hyperextension of the head and vertebral artery dissection) or chest trauma (which occurs during the vulnerable period of repolarization, with about 10 to 30 ms before the peak of T wave, it implies the involvement of K channels – unelucidated mechanisms).
Despite the polymorphism of cardiovascular diseases that can cause sudden death and the difficulties of diagnosis, evaluation is mandatory before enrollment in a competitive sporting activity at least through a careful history and thorough physical evaluation. Even if ECG and echocardiography remain optional, these are useful in detecting various anomalies and in selecting cases that require further explorations. Reevaluation of athletes must be done regularly at two years. We must not forget the false-positive examinations which may disqualify/discourage competitive sport, with sometimes dramatic consequences for the athlete and his family.
Although sudden death is a rare event, the devastating impact it has justifies disqualification from competitions if there is a suspicion of risk of major cardiovascular events.