Significance of appropriate defibrillator shock 3 hours and 20 minutes following implantation in a patient with hypertrophic cardiomyopathy

Early Defibrillator Shock. Introduction: Implantable defibrillators have proved effective in terminating potentially life-threatening ventricular tachyarrhythmias in hypertrophic cardiomyopathy (HCM), although the timing of appropriate shocks may be exceedingly variable. Methods and Results: We report an unusual occurrence in a 48-year-old woman with nonobstructive HCM who experienced an appropriate shock for ventricular fibrillation only 3 hours and 20 minutes after implantation. Careful review of the clinical circumstances failed to define a specific mechanism related to the implant procedure that could have triggered the potentially lethal arrhythmia. Conclusion: Early device interventions are not uncommon in HCM, but (as in this case) appear unrelated to mechanisms other than the unpredictable and underlying arrhythmogenic substrate in this disease.