Bradycardia-Induced Monomorphic VT in Dilated Cardiomyopathy: Insights From ICD Upgrade Cases.

AIMS: Bradycardia-induced monomorphic ventricular tachycardia (VT) is an underrecognized proarrhythmic mechanism in dilated cardiomyopathy (DCM). This case series describes patients with advanced heart failure and recurrent VT/ventricular fibrillation in whom upgrading from single- to dual-chamber implantable cardioverter-defibrillators (ICDs) provided arrhythmia suppression.

METHODS

Three patients with DCM, recurrent sustained VT/ventricular fibrillation, and hemodynamic instability due to bradycardia, pacing-related cycle-length variability, and loss of atrioventricular (AV) synchrony were retrospectively analyzed before and after ICD upgrade.

RESULTS

All patients demonstrated bradycardia-triggered monomorphic VT and clinical deterioration during ventricular pacing without AV synchrony. Upgrading to a dual-chamber system with atrial pacing corrected bradycardia, normalized cycle length, restored AV synchrony, and reduced arrhythmia burden. Two patients underwent heart transplantation under improved conditions, and 1 patient remained arrhythmia-free during long-term follow-up.

CONCLUSIONS

Dual-chamber ICD upgrade offers an effective strategy for preventing bradycardia-induced monomorphic VT in advanced DCM by stabilizing heart rate and eliminating proarrhythmic pacing sequences.