Acute effect of nonsurgical septal reduction therapy on regional left ventricular asynchrony in patients with hypertrophic obstructive cardiomyopathy

Background - Patients with hypertrophic obstructive cardiomyopathy have left ventricular (LV) diastolic dysfunction due, in part, to temporal heterogeneity in regional function. The acute effect of the relief of LV outflow tract obstruction is unknown. Therefore, we investigated the effects of nonsurgical septal reduction therapy (NSRT) on regional function. Methods and Results - Twenty-two patients (aged 56±17 years) underwent echocardiographic examination, including tissue Doppler imaging, simultaneously with left heart catheterization before and after NSRT. LV regional function was assessed in 12 segments from which myocardial strain was obtained. Asynchrony was calculated as the coefficient of variation of the time interval from the QRS complex to the onset of expansion and to early diastolic strain. After NSRT, a significant reduction in LV outflow tract obstruction (from 57 ± 5 to 12 ± 3 mm Hg) occurred with shortening of the time constant of LV relaxation (71±4 to 61±3 ms; both P<0.05). The coefficient of variation of the time interval to onset of regional expansion decreased significantly and related well to the changes in the time constant of LV relaxation (r=0.81, P<0.01). Conclusions - NSRT has a favorable effect on LV regional asynchrony, which accounts for the acute changes in LV relaxation.