Nitroglycerin as an adjunct to hypothermic hyperkalemic cardioplegia

The efficacy of nitroglycerin as an adjunct to hyperkalemic hypothermic cardioplegia was assessed by measurement of changes in coronary vascular resistance. Thirty patients undergoing coronary artery bypass grafting were studied. During a 1000 ml infusion of cardioplegia, a bolus of 1 mg of nitroglycerin or control solution was injected while the infusion rate was kept constant. Measurement of aortic root pressure allowed calculation of coronary vascular resistance. There was a mean decrease of 21.2% in coronary vascular resistance after a bolus of 1 mg of nitroglycerin was injected in the study group (p less than .001, n = 15); there was no significant change in resistance in the control group. There was also no significant change in systemic vascular resistance in either group. A retrospective blind analysis of the anatomic angiographic features of the heart with a quantitative assessment of both coronary stenoses and coronary collaterals was made. There was no correlation between coronary scores and preinjection coronary vascular resistance. There was also no correlation between collateral scores and the change in coronary vascular resistance with nitroglycerin. These results suggest that nitroglycerin is an effective coronary vasodilator when used as an adjunct in hypothermic hyperkalemic cardioplegia and that baseline coronary vascular resistance or change in coronary vascular resistance with nitroglycerin cannot be predicted on the basis of current assessments of coronary angiograms.