Clinical impact of nonsustained ventricular tachycardia recorded by the implantable cardioverter-defibrillator in patients with hypertrophic cardiomyopathy.

BACKGROUND: Nonsustained ventricular tachycardia (NSVT) is a risk factor for sudden death (SD) in hypertrophic cardiomyopathy (HCM). Implantable cardioverter-defibrillators (ICDs) enable accurate assessment of NSVT burden and characteristics. In a cohort of HCM patients with ICD, we characterized Holter- and ICD-retrieved NSVT and evaluated their relationship with prognosis. METHODS AND
RESULTS: We studied a cohort of consecutive HCM patients who underwent Holter ECG before receiving a primary prevention ICD. Patients were followed from ICD implantation to the first appropriate ICD therapy. We evaluated the association of NSVT characteristics with ICD interventions. Study cohort included 51 HCM patients (28 males, mean age: 48 ± 15 years). Thirty-four patients (66%) had NSVT at pre-ICD Holter ECG. Out of 17 patients with negative baseline Holter, 7 (41%) showed ICD-NSVT. In patients with both Holter- and ICD-NSVT, these latter were faster (199 ± 27 bpm vs. 146 ± 24 bpm; P < 0.001) and longer (16 ± 8 beats vs. 10 ± 11 beats; P = 0.008) than Holter-NSVT. During follow-up (38 ± 24 months), 11 patients (22%) experienced appropriate ICD therapy. NSVT length in beats (hazard ratio [HR]: 1.05; 95% CI: 1.00-1.10; P = 0.02) but not heart rate (HR: 1.00; 95% CI: 0.98-1.02; P = 0.86) predicted ICD intervention. A simple index of NSVT severity (heart rate × length in beats/100 >28) predicted ICD intervention (HR: 5.45; 95% CI: 1.10-27.32; P = 0.03).
CONCLUSIONS: Long-lasting and rapid NSVT recorded during continuous rhythm monitoring predict appropriate ICD intervention in high-risk HCM patients. Further studies should assess whether prolonged rhythm monitoring may assist in evaluating patients at intermediate risk of SD, in which the decision to implant an ICD needs to be individualized.