Effects of varied cardioplegic perfusion pressure on myocardial preservation with critical coronary stenosis.

Inadequate delivery of cardioplegic solution distal to coronary artery stenosis may result in increased injury during ischemic arrest. This study was performed to determine the effects of cardioplegic perfusion pressure on cardioplegia delivery and myocardial preservation in hearts with critical coronary artery stenosis. Twenty dogs underwent 90 minutes of cold potassium cardioplegic arrest with partial occlusion of the circumflex coronary artery. Group 1 received cardioplegia at 50 mm Hg pressure, Group 2 at 90 mm Hg pressure, and Group 3 at 130 mm Hg pressure. It was found that cooling rates were 5.4 degrees, 9.1 degrees, and 18.2 degrees C per minute in the nonischemic area (p = 0.004) and 2.0 degrees, 4.5 degrees, and 7.9 degrees C in the ischemic area (p = 0.008) in Groups 1, 2, and 3, respectively. Total of cardioplegic solution flows were 86, 188, and 262 ml per minute per 100 gm in Groups 1, 2, and 3, respectively (p = 0.001). However, flow did not differ significantly between groups in the ischemic area. Rate of rise of left ventricular (LV) pressure decreased significantly in Groups 1 and 2 but not in Group 3 (p = 0.002). Other measured variables did not differ significantly between groups, although LV function curves showed less deterioration in the high-pressure groups. It is concluded that higher cardioplegic perfusion pressure resulted in more rapid cooling in normal and ischemic areas and slightly better preservation of ventricular function as measured by some indexes. However, preservation was generally good for each of the pressures for up to 90 minutes of ischemia when the septum was consistently cooled to 10 degrees C.