2012 Volume 71 Issue 6 Pages 447-455
Cardiac arrhythmia is an uncommon cause of faintness and presyncope. Both bradycardia and tachycardia may induce a transient drop of blood pressure followed by reduction of cerebral blood flow, which evokes faintness and presyncope. The most frequent cause of faintness/presyncope is a neurally mediated reflex, and cardiac arrhythmia is the second common cause in the general population. Since several severe types of arrhythmias may induce sudden death, it is important to recognize faintness and presyncope as a warning sign for further potentially lethal arrhythmic events in selected patients. Taking a detailed medical history and recognition of the accompanied symptoms allows the practitioner to distinguish cardiogenic faintness/presyncope from a neurally mediated one. A definitive diagnosis of cardiogenic faintness/presyncope should be performed by clarifying the direct relationship between the symptoms and documented arrhythmia. However, conventional 12-lead electrocardiography (ECG) and ultrasound echocardiography are useful for risk stratification of faintness/presyncope even after disappearance of the symptoms. Holter ECG and event recorders are widely used for detection of arrhythmic events related with faintness/presyncope. Bradycardia may evoke faintness. However, bradycardia without significant cardiac pause usually accompanies shortness of breath, but not faintness or presyncope. Sudden cardiac pause, with or without preceding tachycardia, is a major cause of faintness/presyncope. Tachycardia is the most important cause of faintness and presyncope. Both supraventricular tachycardia and ventricular tachycardia can cause faintness/presyncope. Of note, faintness and presyncope related with ventricular tachycardia in patients with impaired cardiac function should be evaluated carefully by assessing the risk of sudden cardiac death. Several types of ventricular tachycardia and fibrillation, including Brugada's syndrome, also may cause sudden death. A thorough examination must be performed to clarify the risk of sudden death in patients having these conditions. In conclusion, careful evaluation of faintness and presyncope taking possible involvement of arrhythmia into consideration is important to predict and prevent sudden cardiac death.