Myocardial temperature mapping. Improved intraoperative myocardial preservation.

An improved approach to intraoperative myocardial preservation technique to ensure uniform myocardial cooling past critically stenosed arteries was developed for patients undergoing aorta-coronary bypass grafting. Proximal anastomoses are done and then, after institution of cardiopulmonary bypass, a separate roller pump head is used to administer a specific controlled volume of cardioplegic solution (1 L) through a 4 degrees C coil to provide controlled pressure in the root of the cross-clamped aorta. Midmyocardial wall temperatures in the anterior, posterolateral, inferior, and septal walls of the left ventricle are measured. Distal anastomoses are then performed sequentially, beginning with the warmest region. After each distal anastomosis, 400 ml of cardioplegic solution are again administered into the aortic root. This approach has been used in 100 consecutive patients from July, 1979, through July 1980 (Group I). and these patients were compared to 97 consecutive patients undergoing aorta-coronary bypass grafting in the previous year (July, 1978, through June, 1979) (Group II) who had myocardial preservation with potassium cardioplegia administered by syringe injection and without regional temperature mapping. There were no perioperative myocardial infarctions in Group I: there were five (5.2%) in Group II (p less than 0.05). A significant reduction in cardiac deaths was also achieved, with two (2.0%) such deaths in Group I and eight (8.2%) in Group II (p less than 0.05). The data suggest that delivery of adequate volumes of cardioplegia solutions by a pressure-regulated system, in combination with myocardial temperature mapping to determine the sequence of bypass grafting, can improve myocardial preservation.