Effect of verapamil on systolic and diastolic coronary blood flow velocity in asymptomatic and mildly symptomatic patients with hypertrophic cardiomyopathy

OBJECTIVE To assess non-invasively the effect of verapamil treatment on coronary blood flow velocity in asymptomatic and mildly symptomatic patients with hypertrophic cardiomyopathy. DESIGN High frequency transthoracic Doppler echocardiography was used to compare resting phasic coronary blood flow velocity before and after a one month period of verapamil treatment in 17 patients (14 men and three women) with non-obstructive hypertrophic cardiomyopathy. Eighteen healthy subjects formed an age and sex matched control group. Systolic and diastolic coronary blood flow velocity was measured in the distal portion of left anterior descending coronary artery using high frequency transthoracic Doppler echocardiography. Blood flow velocity before and after verapamil was compared in the patients with cardiomyopathy and with the results in the control group. RESULTS Compared with the controls, patients with hypertrophic cardiomyopathy had increased diastolic coronary blood flow velocity (41.8 (8.1) v 59.9 (21.9) cm/s, p < 0.01) and a lower mean systolic coronary blood flow velocity (18.7 (10.8) v −11.2 (27.5) cm/s, p < 0.01) before verapamil treatment. A backward pattern of systolic flow, manifested by negative values of coronary blood flow velocity, was recorded in eight of the patients, while no negative values were found in the controls. After verapamil treatment the retrograde systolic blood flow was restored to an anterograde pattern in only one patient. The mean value of systolic coronary blood flow velocity did not change significantly and remained lower than the systolic forward flow velocity in the controls (−3.6 (31.8) v18.7 (10.8) cm/s, p < 0.05). However, diastolic coronary blood flow velocity decreased significantly after verapamil (59.9 (21.9)v 50.7 (19.5) cm/s p < 0.05), reaching a level comparable with that in the controls (50.7 (19.5)v 41.8 (8.1) cm/s, p > 0.05). CONCLUSIONS In contrast to healthy subjects, in non-obstructive hypertrophic cardiomyopathy the systolic pattern of coronary blood flow was heterogeneous (both retrograde and anterograde), and diastolic coronary blood flow velocity was abnormally increased, despite a lack of significant symptoms. Verapamil treatment did not restore the forward pattern of systolic blood flow but decreased diastolic blood flow velocity to a level comparable with that in healthy subjects.