Successful treatment of ventricular fibrillation storm triggered by short-long-short sequence; time to avoid managed ventricular pacing.

Sudden cardiac death (SCD) in hypertrophic cardiomyopathy (HCM) is caused by ventricular tachyarrhythmia that can be effectively treated by implantable cardioverter defibrillator (ICD) therapy. We report of a 28-year-old man with HCM and a dual chamber ICD, originally implanted for primary prevention of SCD, (programmed to AAI(R)-DDD(R); managed ventricular pacing (MVP) mode, Medtronic Inc. St Paul, MN USA). He presented with recurrent ICD shocks due to ventricular fibrillation (VF) despite antiarrhythmic therapy. Careful assessment of the stored electrograms demonstrated a repetitive pattern of VF initiation following short-long-short sequences. Initially, activation of ventricular rate stabilization (VRS) algorithm failed to prevent recurrent VF. Ultimately, deactivation of MVP and reprogramming the device to DDD mode with VRS on, resulted in arrhythmia suppression and avoidance of ICD shocks. Physicians should be aware that although VRS function is available in MVP mode, it does not function in the AAI mode during MVP; in order to effectively treat short-long-short sequence induced ventricular arrhythmia by device programming.