Immediate appearance of coronary collaterals during ergonovine-induced arterial spasm.

Angiographically demonstrable collateral flow occurred immediately when coronary arterial spasm was induced by ergonovine in two patients with angina who had organic stenosis of less than 40 percent. These findings suggest that coronary collaterals may develop in response to intermittent brief myocardial ischemia in man, and that collaterals may be preserved even if they are closed at rest and can immediately function when a coronary artery is acutely occluded.