| Abstract: | The effect of varying the mode of cardioplegic delivery and the presence of regional wall motion abnormalities on myocardial protection by crystalloid cardioplegic solutions was assessed in 68 patients undergoing coronary artery bypass grafting. Serial transmural biopsy specimens from the left ventricular apex were assayed for adenosine triphosphate. All patients had more than 75% stenosis of the left anterior descending coronary artery. They were prospectively randomized into Groups I and II to receive (I) all cardioplegic solution infused via the aortic root or (II) reinfusions of cardioplegic solution given both centrally and through the completed distal left anterior descending anastomosis. Patients were also stratified as to the presence of normal (N) or impaired (Ab) apicoanterior regional wall motion. Inadequate delivery of cardioplegia during ischemia in Group I was manifested by a 41% (p less than 0.01) depletion of adenosine triphosphate stores in abnormally contracting myocardium distal to the left anterior descending stenosis that was not repleted after restoration of coronary flow and a 27% (p less than 0.05) decline in ATP stores during reperfusion in myocardium with normal preoperative wall motion. In contrast, nucleotide stores were preserved at preischemic levels throughout ischemia and reperfusion in Group II regardless of preoperative wall motion. Preservation of ATP did not correlate with duration of ischemia, highest recorded septal temperature, or volume of cardioplegic solution infused. Two patients in each group had a new perioperative infarction. However, 38% of patients in Group IAb required transient inotropic support versus 5% in Group IIAb (p less than 0.05). These data emphasize that reinfusion of cardioplegic solutions distal to coronary obstructions is mandatory for optimal myocardial protection during coronary revascularization. |
