Syncope and Ventricular Tachycardia: Revisiting the Evidence Base

Syncope is common across cardiac disorders, yet its arrhythmic mechanisms are often misattributed. A pivotal point is frequently overlooked: sustained ventricular tachyarrhythmias (VT) are not self-terminating.

We synthesize evidence from community ED cohorts, ILR registries, and ICD trials to clarify when ventricular rhythms can plausibly explain brief, self-limited loss of consciousness. Across structural heart disease and inherited conditions, sustained monomorphic or polymorphic VT, when they occur, persist or degenerate and require device/external termination; by nature, they rarely cause transient syncope. The sole exception that commonly self-terminates and can present with syncope is torsades de pointes (TdP), that can occur in the setting of prolonged repolarization. By contrast, nonsustained VT (NSVT), typically short monomorphic runs, can indicate the severity of the underlying cardiopahty in some patients, but it is very rarely a direct cause of syncope.

Given that sustained ventricular arrhythmias are non-self-terminating, the evaluation of syncope should prioritize bradyarrhythmic and hypotensive/reflex mechanisms and reserve a VT hypothesis for narrowly defined contexts. This approach is consistent with real-world device and registry data, in which malignant ventricular arrhythmias remains a rare cause of syncope.