Changes in human coronary flow reserve after administration of intracoronary diltiazem

Epicardial coronary artery diameter (ECAD), coronary blood flow velocity (CBFV), and coronary flow velocity reserve (CFVR) were analyzed at baseline and after a 500 micrograms i.c. bolus of diltiazem in nonstenotic coronary arteries of awake humans. Furthermore, patients (n = 25) were first randomized to pretreatment either with placebo (n = 12) or isosorbide dinitrate (0.5 micrograms/kg/min infusion) (n = 13). Diltiazem resulted in a significant increase in epicardial diameter (+10%; p = 0.001) and in coronary blood flow (CBF) (+30%; p = 0.0001). Whereas basal CBFV only slightly increased (+7%; NS), there was a significant fall in CFVR (-11%; p = 0.001). The increase in coronary diameter and CBF after administration of i.c. diltiazem was comparable in placebo- and nitrate-pretreated patients. The decrease in CFVR, however, was restricted to the placebo-pretreated patients (-21%; p = 0.0004). Apparently, diltiazem attenuated the CFVR but only in the absence of nitrates. Thus, diltiazem i.c. appears to enhance myocardial oxygen supply without deleterious effects on the distal coronary perfusion pressure.