"Reverse coronary steal" induced by coronary vasoconstriction following coronary artery occlusion in dogs

The phenomenon of "coronary steal," i.e., the shunting of blood from ischemic to normally perfused areas of myocardium, has been described as an effect of the administration of several vasodilating agents. This study was performed to ascertain whether the reverse situation can be induced, i.e., whether vasoconstriction of the vessels supplying the nonischemic zone could increase the collateral flow to the ischemic area. In 16 open chest dogs, 15 and 30 min after occlusion of the left anterior descending coronary artery, epicardial electrograms were recorded and regional myocardial blood flow (RMBF) was measured with radiolabeled microspheres. Methoxamine was infused intravenously between 17 and 30 min, the mean arterial pressure being kept constant. The results indicate that while the coronary arterial flow to the normal myocardium fell from 90.6 +/- 4.3 to 77.7 +/- 3.2 ml/min/100 g (P less than 0.01), the collateral blood flow to the ischemic area increased from 21.4 +/- 3.5 to 41.0 +/- 4.2 ml/min/100 g (P less than 0.01), and thereby reduced acute myocardial ischemic injury. This favorable redistribution of blood flow might be considered a "reverse coronary steal."