Effect of intravenous dipyridamole on regional coronary blood flow with 1-vessel coronary artery disease: evidence against coronary steal.

The effects of i.v. dipyridamole were studied in 9 patients with isolated total left anterior descending coronary artery (LAD) obstruction, in 6 patients with isolated 90 to 99% diameter reduction of the LAD and in 10 patients with normal coronary arteries and normal left ventricular function. Coronary sinus and great cardiac vein flows were determined by continuous thermodilution. Flows were measured at rest and 1, 3, 5 and 10 minutes after i.v. dipyridamole. Great cardiac vein flow represents the venous outflow from the LAD territory. In the presence of coronary steal from the LAD territory, great cardiac vein flow is expected to decrease while coronary sinus flow increases. Intravenous dipyridamole induced a similar flow increase in the coronary sinus and the great cardiac vein in all 3 groups (p less than 0.001 between rest and dipyridamole, difference not significant among groups), suggesting that no coronary steal was induced. The maximal increase in great cardiac vein flow was 118 +/- 74% in the control group, 86 +/- 74% in the group with 90 to 99% LAD obstruction and 102 +/- 29% in the group with total LAD obstruction (difference not significant). These data show that i.v. dipyridamole produces a similar increase in coronary flow in ischemic and nonischemic areas and suggests that an increase in collateral flow is the underlying mechanism for increased flow to the ischemic area.