Sudden death is defined as unexpected death as a result of natural causes (non traumatic, nonviolent) in which a loss of all functions occurred instantaneously or within 1 hour of the onset of collapse symptoms. Sudden death was considered to be cardiovascular (SCD) in origin when at postmortem the primary cause leading to cardiac arrest was found in the heart or great vessels and other non-cardiac causes were excluded.  

More than 20 pathologic entities have been identified as causes of SCD in young athletes.

Hypetrophic Cardiomyopathy (HCM) is characterized by abnormal hypertrophy, primarly of the left ventricle. Sudden death in patients with hypertrophic cardiomyopathy is primarily due to ventricular arrhythmias secondary to intrinsic abnormalities in the heart muscle that can occur  during exertion, leading to myocardial ischemia. Physical examination of patients may be completely normal since abnormalities may not be present at rest but only during exercise. The majority of patients (75%-95%) will have an abnormal electrocardiogram (ECG). The gold standard for diagnosis of HCM is 2-dimensional echocardiography, illustrating ventricular hypertrophy without chamber dilatation. The early diagnosis of HCM may be difficult to make in competitive athletes. Since HCM may mimic athletic heart syndrome, a 2-3 months period of athletic deconditioning may be recommended with repeat echocardiographic imaging to ensure resolution of ventricular hypertrophy due to intensive training. HCM is an inheritable disorder with variable penetrance; a detailed family history is an important tool for screening young athletes.

Arrhythmogenic Right Ventricular Cardiomyopathy (ARVD) is an inherited cardiomyopathy characterized by right ventricular dysfunction secondary to fibrofatty replacement of cardiac myocytes. Clinically, patients may be completely asymptomatic or have symptoms such as syncope, palpitations, dizziness, often with exertion. Up to 40% of ECGs may be normal. Approximately a third of the patients have a positive family history. Mortality is most often due to lethal ventricular arrhythmias or progressive heart failure.

Coronary Artery Anomalies - the most common heart blood vessels anatomy associated with risk of sudden death is the left main coronary artery arising from the right sinus of Valsava with an intra-arterial course between the aorta and pulmonary artery. Resting ECGs are typically normal and exercise testing may be negative. Echocardiography is a reliable method for identifying the anomalies of the left main and right coronary artery.    

Congenital Long QT Syndrome - inherited abnormalities affecting cardiac ion channels cause abnormal repolarization, leading to torsades de pointes (form of polymorphic ventricular tachycardia) that can lead to syncope, seizures, and sudden death.

Wolff-Parkinson-White Syndrome (WPW) - during sinus rhythm, antegrade conduction down the accessory pathway causes ventricular preexcitation resulting in delta wave on ECG. Risk stratification: with invasive electrophysiology testing for patients with symptomatic and asymptomatic WPW.

Brugada Syndrome - inherited disorder that can lead to spontaneous lethal ventricular arrhythmias. ECG finding may be transient and include a right bundle branch block pattern and ST segment elevation in the right precordial leads (V1-V3). Syncope or sudden death events often occur at rest or at night and usually appear in the third to fourth decades of life.

Myocarditis - is an inflammatory condition of infectious origin. The infected myocardium becomes inflamed, creating an unstable site where a potentially terminal arrhythmia may arise.

Prepared by: Dr. Nenad Radivojevic

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