Relation of delayed intrinsicoid deflection of the QRS complex to sudden cardiac death in patients with hypertrophic cardiomyopathy

Aims: Predictors of sudden cardiac death (SCD) in patients with hypertrophic cardiomyopathy (HCM) do not include ECG variables. Intrinsicoid deflection (ID) represents the early ventricular depolarization on surface ECG. Delayed ID (DID) has been associated with sudden cardiac arrest (SCA) in the community. In a cohort of consecutive patients with HCM, we assessed whether DID predicts SCA or its surrogates. Methods: We reviewed ECG, clinical and follow-up data of 344 consecutive HCM patients. DID (ID >= 50 ms) was classified as lateral (leads I or aVL), inferior (leads II, III or aVF), and precordial (leads V5 or V6). The endpoint was a combination of SCD, resuscitated SCA or appropriate ICD intervention. Results: The SCA group was composed by 2 secondary prevention ICD recipients and 23 patients that reached the endpoint during follow-up (108 +/- 73 months). SCA patients had more frequently massive LV hypertrophy (LVH) or end-stage HCM. ECG indexes of LVH were comparable between SCA and controls. SCA patients were more likely to have DID on ECG lateral leads I/aVL (72% vs 44%; p = 0.008). A non significant trend was observed for inferior and V5/V6 leads. DID I/aVL was associated with SCA in multivariate analysis after correction for massive LVH and end-stage disease (HR: 2.86; 95%CI: 1.14-7.13; p = 0.02). Conclusions: In HCM patients DID is associated with increased risk of SCA. Its prognostic value extends beyond that of LVH. If confirmed in prospective studies, the prognostic power of this ECG marker could be used to refine risk prediction.