Does retrograde warm blood cardioplegic perfusion provide better protection of ischemic areas than antegrade warm blood cardioplegic perfusion? A magnetic resonance study in pig hearts

Objective: The purpose of this study was to determine whether retrograde continuous normothermic blood cardioplegic perfusion provides better protection to ischemic areas of the left and right ventricles than does antegrade continuous normothermic blood cardioplegic perfusion. Localized phosphorus 31 magnetic resonance spectroscopy was used to monitor the changes in energy metabolism and intracellular pH in the ventricles of pig hearts. Methods: Ten isolated pig hearts received 20 minutes of antegrade continuous normothermic blood cardioplegic perfusion for collection of control (baseline) data, followed by 60 minutes of either antegrade continuous normothermic blood cardioplegic perfusion (n = 5) or retrograde continuous normothermic blood cardioplegic perfusion (n = 5) with occlusion of the left anterior descending and the right coronary arteries. The hearts were then subjected to antegrade continuous normothermic blood cardioplegic perfusion for 20 minutes. The perfusion pressures were maintained between 80 and 100 mm Hg and between 38 and 43 mm Hg during antegrade and retrograde continuous normothermic blood cardioplegic perfusions, respectively. Intracellular pH and creatine phosphate, inorganic phosphate, and adenosine triphosphate levels were measured continuously in each ventricle by means of localized phosphorus 31 magnetic resonance spectroscopy with 2 surface coils. Results: Both antegrade and retrograde continuous normothermic blood cardioplegic perfusion resulted in a significant increase in inorganic phosphate level and decreases in creatine phosphate level, adenosine triphosphate level, and intracellular pH. No significant differences in these changes were observed between the two groups. The creatine phosphate and adenosine triphosphate levels were significantly lower in the right ventricle than in the left ventricle during retrograde continuous normothermic blood cardioplegic perfusion. On reperfusion, the inorganic phosphate level, creatine phosphate level, and intracellular pH recovered completely; however, no recovery in the adenosine triphosphate level was seen in the ventricles of either group. Conclusions: Retrograde continuous normothermic blood cardioplegic perfusion does not provide better protection to ischemic areas of the ventricles titan does antegrade continuous normothermic blood cardioplegic perfusion under our experimental conditions.