Effects of Heart Rate and Arterial Blood Pressure on Coronary Collateral Blood Flow in Dogs

ABSTRACT The Krypton 85 clearance technique was used for studying the effects of induced changes in heart rate and arterial blood pressure on the collateral blood flow of the myocardium during acute coronary occlusions in dogs. Collateral blood flow was little affected by variations in heart rate although a slight improvement of flow was seen at frequencies between 90 and 130 beats/min compared to higher frequencies. Arterial blood pressure is an important determinant of coronary collateral blood flow in the non‐failing heart, but the pressure‐flow relationships indicate a passive behaviour of the collateral vessels. Ventricular dilatation with elongation of the collateral vessels and increased intramural pressure seems to impede collateral flow. The size of the ischemic region produced by the coronary occlusion is not significantly altered by changes in heart rate or blood pressure.