Angiographic findings in patients exhibiting ischemia after oral dipyridamole.

We have assessed the angiographic features of a group of 37 patients given oral dipyridamole and 37 patients given matching placebo. Both groups represented severe coronary arterial disease and were studied prior to bypass surgery. Six patients (16%) had angina and 13 patients (35%) had electrocardiographic changes after dipyridamole. All the patients in the control group were nonresponders. In the group given dipyridamole the patients responding with angina had significantly more compromised collaterals than the patients without chest pain (P = 0.021). The same applied to the patients with electrocardiographic changes versus those with no electrocardiographic changes (P = 0.034). No differences between responders and nonresponders could be found in terms of the severity of coronary arterial disease, severity of anginal symptoms, exercise tolerance, antianginal medication, number of past myocardial infarctions, and left ventricular ejection fraction. In conclusion, the data strongly suggest that ischaemic responses to dipyridamole originate from myocardial steal accentuated by compromised flow in collateral vessels.