Association between intraventricular myocardial systolic dyssynchrony and ventricular arrhythmias in patients with hypertrophic cardiomyopathy

Background: The distribution and magnitude of left ventricular (LV) hypertrophy are not uniform in patients with hypertrophic cardiomyopathy (HCM), which results in regional heterogeneity of LV systolic and diastolic function. The aim of the study was to evaluate LV regional systolic asynchrony in patients with HCM by pulsed Doppler myocardial imaging (DMI). Methods: We studied 35 HCM patients and 45 age- and sex-matched controls. By the use of DMI, the following five different basal myocardial segments were measured: systolic peak velocity (Sm); early- and late-diastolic peak velocities; pre-contraction time (Q-Sm) (from the beginning of Q-wave of ECG to the onset of Sm); intraventricular systolic delay (IntraV-Del) (difference of Q-Sm in different LV myocardial segments); interventricular delay (InterV-Del) (difference of Q-Sm between the most delayed LV segment and right ventricular lateral wall). Results: DMI analysis showed in HCM lower myocardial systolic and early-diastolic peak velocities of all the analyzed segments. As for time intervals, controls showed homogeneous systolic activation of the ventricular walls. Conversely, HCM group, despite the absence of intraventricular conduction defects by surface ECG, showed significant both Inter- and IntraV-Del (P < 0.0001). Linear regression models pointed out independent positive associations of IntraV-Del with LV outflow gradient and septal wall thickness in HCM (P < 0.001). An IntraV-Del > 30 msec well differentiated controls and HCM. In addition, an IntraV-Del > 45 msec (ROC curve) identified a subgroup of HCM patients with nonsustained ventricular tachycardia during Holter monitoring (90.9% sensitivity and 95.8% specificity). Conclusions: The impairment of intrarventricular systolic synchronicity is strongly related to increased septal thickness and LV outflow-tract gradient in HCM. DMI analysis may be able to select subgroups of HCM patients at an increased risk of ventricular tachyarrhythmias.