Ventricular fibrillation induced by atrial threshold search: a case report

Automatic threshold measurement algorithms are intended to ensure effective myocardial capture and enhance safety but can sometimes inadvertently cause arrhythmias. The underlying mechanism in this case may be related to the switch from biventricular to right ventricular (RV)-only pacing during Atrial Capture Management, which increases dispersion in repolarization, facilitating early afterdepolarizations and triggering polymorphic tachycardias. Notably, newer ICD models mitigate this risk by maintaining biventricular pacing during this test. This case underscores the need for careful programming and monitoring of ICD algorithms.