Impact of Short Acting Disopyramide on Left Ventricular Mechanics Evaluated by Strain Analysis in Patients with Hypertrophic Obstructive Cardiomyopathy

Background: Disopyramide is often used as a second line treatment for the relief of left ventricular outflow tract obstruction (LVOTO) in symptomatic patients with hypertrophic obstructive cardiomyopathy (HOCM). It has negative inotropic effect on the left ventricle, but the exact mechanism of action is unknown.

Methods: Prospective single center study from the hypertrophic cardiomyopathy clinic at Beilinson Hospital, Rabin Medical Center. Thirteen patients with HOCM being treated with short acting disopyramide had a comprehensive echocardiographic assessment prior to the intake of the morning dose (ECHO 1, at 8:30 AM for all patients) and 2:30hrs after the intake of disopyramide (ECHO 2).

Results: Of the 13 patients, 10 were male, average age was 66.7 years. Eleven patient were on a beta blocker medication. Disopyramide intake caused reduction in global longitudinal strain with average strain peaks of -14±2 vs -17 ±2 (ECHO 2 and ECHO 1, respectively; p = 0.00009). Interestingly, this difference was segmental noted mainly in the longitudinal strain of the basal septum (-10±4 vs. -15±6, p=0.008) in the apical anterior segment (-9± 4 vs -15±5, p=0.003) and in the basal posterior segment (-15.5 vs. -18±6 - p = 0.005). There was no significant reduction in the ejection fraction (EF) or the peak LVOT gradient.

Conclusions: The negative inotropic effect of Disopyramide on the left ventricle in patient with HOCM is not diffuse but acts selectively, especially in the basal septal segment with the maximal wall thickness. The assessment of LV contractility in HOCM immediately after intake of Disopyramide is not concordant with LVEF