Delivery pressure of the cardioplegic solution influences myocardial protection.

To investigate whether cardioplegic solution (CS) delivery pressure influences myocardial protection, intermittent infusions of CS at different pressures were used in an isolated Langendorff rat heart preparation. In group 1 the hearts were kept arrested for 210 min at 12 degrees C with intermittent infusions of 5 ml CS every 20 min at 30 cm H2O (22 mmHg) pressure, in group 2 the same volume of CS was infused at 100 cm H2O (73.5 mmHg) pressure, in group 3 at 145 cm H2O (106.5 mmHg) pressure and in group 4 at 238 cm H2O (175 mmHg) pressure. There was a significantly higher coronary resistance in groups 1 and 4 (7.3+/-0.2 RU and 6.9+/-0.2 RU) than in groups 2 and 3 (4.2+/-0.2 RU and 4.2+/-0.2 RU) (P < 0.05) during the ischemic period. There were no significant differences between group 2 and 3 in the reperfusion period. Groups 2 and 3 showed higher coronary flow and left ventricle developed pressure than group 1 and 4. Hearts from group 1 and 4 had Lower adenosine triphosphate (7.88+/-0.44 mu mol.g(-1), 5.56+/-0.56 mu mol.g(-1)) (P < 0.05) and creatine phosphate (24.66+/-0.47 mu mol.g(-1), 15.34+/-0.94 mu mol.g(-1)) (P < 0.05) content at the end of the reperfusion period than group 2 (10.56+/-0.41 mu mol.g(-1), 30.06+/-0.38 mu mol.g(-1)) and group 3 (14.13+/-0.69 mu mol.g(-1), 35.25+/-0.78 mu mol. g(-1)). These results indicate that with antegrade, intermittent, hypothermic, hyperkalemic cardioplegic infusion both a low delivery pressure (22 mmHg) and a high delivery pressure (175 mmHg) are associated with suboptimal myocardial protection.