INTRODUCTION: The prognostic impact of nonsustained ventricular tachycardia (NSVT) morphology has never been explored in hypertrophic cardiomyopathy (HCM). In a single-center cohort of consecutive HCM patients implanted with an implanted cardioverter-defibrillator (ICD), we assessed NSVT morphology patterns and their prognostic implications.
METHODS: A cohort of consecutive HCM patients implanted with an ICD was followed from ICD implantation to last follow-up visit. Patients were assessed for NSVT as stored events in ICD memory. Ventricular tachycardias (VTs) were classified as monomorphic (MM) or polymorphic according to intracardiac electrogram morphology.
RESULTS: One hundred nine consecutive HCM patients (68 males; mean age: 45 ± 17 years) composed the study population. During follow-up (71 ± 48 months), 7 polymorphic NSVT in 4 patients and 370 MM NSVT in 42 patients were retrieved from ICD memory. Among patients with only MM NSVT, 19 (45%) had one morphology, 17 (41%) had two morphologies, 3 (7%) had three morphologies, and 3 (7%) had four morphologies. Patients with polymorphic NSVT had the highest risk of ICD interventions (HR, 5.04; 95% CI, 1.26-20.19; P = .02). A stepwise increase of the risk of ICD interventions in patients with two, three, and four NSVT morphologies was observed. Out of 16 patients with both NSVT and ICD-treated VTs, 13 (81%) had at least one ICD-treated VT with the same morphology of a previous long-lasting NSVT.
CONCLUSIONS: In high-risk HCM patients, the occurrence of polymorphic NSVT and of NSVT with multiple morphologies carries a high risk for ICD interventions. Sustained VTs tend to recur with the same morphology of previous long-lasting NSVTs.