Effect of diltiazem on coronary reactive hyperemia in patients with flow-limiting coronary artery stenosis.

The acute effects of diltiazem on coronary reactive hyperemia were studied in 12 patients with flow-limiting coronary stenosis. Reactive hyperemia was elicited by injection of 8 ml contrast medium into the left coronary artery, while coronary sinus blood flow and left ventricular and aortic pressures were continuously recorded. Relative magnitude of hyperemia was estimated by the ratio of coronary flow at peak hyperemia to baseline flow (hyperemic ratio). Coronary resistance was calculated as the ratio between mean aortic pressure minus left ventricular mean diastolic pressure and coronary sinus blood flow. The 12 patients studied had flow-limiting coronary stenosis since their hyperemic ratio was significantly restrained when compared to that of seven control subjects (1.45 +/- 0.17 vs 2.02 +/- 0.24, respectively; p less than 0.001). The intravenous infusion of diltiazem (0.30 mg X kg-1) reduced heart rate, mean aortic pressure, and myocardial oxygen consumption (all p less than 0.001). After diltiazem the hyperemic ratio was blunted when compared to the basal state (1.36 +/- 0.15 vs 1.45 +/- 0.17, respectively; p less than 0.05), and hyperemia volume was reduced (-33%; p less than 0.001). The decrease in coronary resistance at peak hyperemia was also reduced from -30 +/- 8% to -25 +/- 8% (p less than 0.05). We conclude that diltiazem blunts coronary reactive hyperemia in patients with demonstrated flow-limiting coronary stenosis. This reduction of coronary flow response to a hyperemic stimulus could favorably influence blood flow distribution in patients with significant coronary stenosis.