Sudden Cardiac Death in Athlete

Syncope is defined as a transitory and self-limited loss of consciousness, caused by hypoperfusion of oxygen in brain with spontaneous recovery. Syncope is a frequent clinical entity. Syncope can be the first manifestation of underlying heart disease.
However, syncope occurs frequently in healthy people and athletes, with as much as 8% of athletes referring syncope in last 5 years. It is one of the more important signals for the diagnosis of heart diseases.

Etiology:
* Neurally-mediated reflex syncope: Neurocardiogenic syncope (vasovagal); Carotid sinus syndrome-hypersensitivity; situational syncope; postprandial hypotension

* Rhythm disturbances: bradyarrythmias; sinus node dysfunction; AV conduction system disease; tachyarrythmias; atrial fibrillation and atrial flutter; paroxysmal supraventricular tachycardia; ventricular tachyarrythmias; channelopathies (long QT, short QT, Brugada, malignant early repolarization, cathecolaminergic polymorphic ventricular tachycardia)

* Orthostatic: autonomic failure; primary autonomic failure multiple system atrophy; secondary autonomic failure (diabetic neuropathy, amyloidosis); drugs; volume depletion

* Mechanical/structural: valvulopathies (aortic stenosis); obstructive cardiomyopathy; atrial myxoma; cardiac tamponade; pulmonary embolus

* Cerebrovascular: vascular steal syndromes

* Nonsyncopal attacks: metabolic disorders (hypoglycemia, hypoxia, hyperventilation-hypocapnia); epilepsy; transient ischemic attack; somatization disorders

As in general population, main cause of syncope in athletes is vaso-vagal syncope. When syncope occurs during exercise, it is most often associated with significant cardiomyopathy; in post exercise, or at rest, it is of particular importance but usually vaso-vagal or orthostatic.

The main determinant of risk in patients with syncope is the presence and severity of cardiac disease. Cardiomyopathies are the most important prognostic factor in syncope evaluation, and this is independent of the cause of syncope. In fact, patients with cardiac causes of syncope do not have a higher mortality when compared with their matched controls with similar degrees of heart disease. In this setting, identifying patients with low risk of cardiovascular events or sudden cardiac death can be easily achieved by obtaining clinical data and electrocardiographic features.

The OESIL score can rapidly aid in determining risk of death by estimating a point score based on 4 simple markers namely, age > 65 years, history of cardiac disease (heart failure, CAD, Valvular disease, LV dysfunction), syncope without prodrome, and baseline ECG abnormalities. Patients with a score > 2 have an annual mortality that is greater than 30%. Other markers of poor prognosis include the presentation of syncope during exercise and a family history of sudden cardiac death. In a suspect of cardiac syncope, ECG and echocardiography must be required.

The other investigation tests are Holter, Exercise Testing (indicated only in patients with syncope induced by exercise), Tilt Test (in absence of heart diseases), ATP Test (the positive patients need a pacemaker), Invasive test (Electrophysiological Study and Implantable Loop Recording).