Coronary and systemic vascular resistance during reperfusion after global myocardial ischemia

During controlled aortic root reperfusion after global myocardial ischemia for the performance of coronary artery bypass grafting (N = 16), coronary blood flow was the highest during the first 1 minute to 2 minutes even though the aortic root pressure was controlled at about 40 mm Hg. Even during the period of controlled low pressure, flow began to decline, and the decline continued during the period in which the pressure was controlled at 75 mm Hg. Calculated coronary vascular resistance rose steadily from an initially low value to one well above the normal value for beating hearts. A transient fall in resistance resulted from the administration of a bolus of nitroglycerin into the aortic root. When the initial reperfusate was normokalemic, coronary flow was less and coronary vascular resistance higher during the initial phase of reperfusion. The systemic arterial pressure and resistance fell during the first 1 minute to 3 minutes of reperfusion and in 25% of patients, remained low. The greater the potassium load delivered during the initially hyperkalemic phase, the longer the interval between the beginning of reperfusion and the resumption of cardiac systole.