Thrombosis in one coronary artery causes generalized coronary vasoconstriction in a dog model of unstable angina

We investigated the effect of thrombosis in one coronary artery upon the va scular resistance of another coronary artery. In previous investigations, u sing an animal model of unstable angina, we have observed increased resista nce downstream from thrombus within a left circumflex coronary artery (LCx) stenosis and vasoconstriction of collateral vessels from the left anterior descending artery (LAD) supplying the distal LCx vascular bed. In the pres ent paper, we induced thrombosis within a stenosis of the LCx of 16 beagle dogs, and observed the changes in blood flow to the myocardium supplied by the LAD using the radioactive microsphere technique. This blood flow decrea sed with thrombosis (P = 0.005) in these animals, whereas it did not do so in three time-control experiments. The pressures across the coronary vascul ar bed, i.e. arterial pressure to coronary venous pressure (coronary sinus catheter), did not change. Thus the vascular resistance of the LAD bed incr eased significantly from 147 +/- 11.5 mmHg/ml/sec/g of tissue to 172 +/- 13 .4 mmHg/ml/sec/g of tissue (P = 0.02). As the LAD territory is not perfused with blood from the artery containing thrombus, we conclude that the effec t observed is caused either by release of vasoconstrictors from the thrombu s into the general circulation, or by activation of a neural reflex vasocon striction. The study suggests that unstable angina involving thrombosis in one coronary artery is a global coronary vascular disease.