This study was performed to evaluate coronary flow reserve (CFR) the relation between CFR and exercise capacity and the effects of verapamil, on the CFR in patients with hypertrophic cardiomyopathy (HCMP) using transthoracic doppler echocardiography (TTE).

21 patients with HCMP, and 29 normal controls, were enrolled. The mean diastolic coronary flow velocity (CFmv), and time velocity integral of diastolic coronary flow (CFtvi), were measured in the distal left anterior descending coronary artery, both before, and after dipyridamole infusion. The CFR was defined as the post-dipyridamole CFmv/baseline CFmv ratio. Treadmill tests (TMT) were performed, on 14 patients, to evaluate the relationship between exercise capacity and CFR. The CFR in 7 patients was measured before, and after, verapamil administration.

There were no differences in baseline hemodynamics for the 21 patients with HCMP, compared to the 29 normal controls. The baseline CFmv, and Cftvi, in the 21 patients, were significantly higher than those of the controls (0.40±0.09 vs 0.31±0.06 m/sec, p<0.001, 0.25±0.07 vs 0.16±0.04 m, p<0.001), while the CFR was lower (2.01±0.42 vs 3.06±0.39, p<0.001). The CFR showed negative correlation with the baseline CFmv in patients (correlation coefficient=-0.522, p=0.015). In 14 patients, who performed TMT, neither the CFR nor CFmv correlated with the maximal exercise time. In 7 patients, verapamil administration did not increase CFR.

Because of elevated resting CFmv, and CFtvi, the CFR in patients with HCMP, were reduced. Reduced exercise capacity in patients with HCMP cannot be explained by the reduced CFR. Treatment with verapamil did not increase the CFR.