The effect of verapamil on response of coronary vasomotion to handgrip exercise in symptomatic patients with hypertrophic cardiomyopathy

Objectives. To assess the effect of verapamil on the response of diastolic coronary blood flow velocity (CBFV) and coronary vascular resistance index to handgrip exercise in symptomatic HCM patients. Design. In 13 patients with HCM, the CBFV was detected in the distal portion of left anterior descending coronary artery using high-sensitivity transthoracic Doppler echocardiography. The peak diastolic CBFV and coronary vascular resistance index (calculated as the ratio of mean aortic pressure to CBFV) was measured at baseline and during handgrip exercise. Changes of these parameters induced by the exercise (expressed as the percentage of baseline values) were compared on verapamil treatment and after verapamil withdrawal. The same measurements were obtained in 10 healthy control subject. Results. In HCM patients, the increase in CBFV during exercise was significantly higher on than off verapamil therapy (16.2 +/- 5% versus 6.8 +/- 3.8%, p < 0.001). In healthy controls, exercise-induced increase in CBFV was comparable to CBFV changes in HCM patients receiving verapamil (17.4 +/- 5.7 versus 16.2 +/- 5%, p < 0.05) and was significantly greater than the CBFV response in HCM patients off verapamil (17.4 +/- 5.7% versus 6.8 +/- 3.8 % p < 0.005). During exercise the coronary vascular resistance index decreased on verapamil and increased after drug withdrawal (-5.8 +/- 5.6% versus 1.1 +/- 5.1%, p < 0.001). In healthy controls the coronary vascular resistance index decreased during exercise -8.5 +/- 4.5% to similar extent as in HCM patients on verapamil. Conclusion. In HCM symptomatic patients, verapamil improved coronary vasomotor response to physical stress. Verapamil was able to restore adequate vasodilator response to handgrip exercise.