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 co ntinuous normothermic blood cardioplegic perfusion provides better protecti on to ischemic areas of the left and right ventricles than does antegrade c ontinuous normothermic blood cardioplegic perfusion. Localized phosphorus 3 1 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 normoth ermic blood cardioplegic perfusion for collection of control (baseline) dat a, 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 descend ing and the right coronary arteries. The hearts were then subjected to ante grade continuous normothermic blood cardioplegic perfusion for 20 minutes. The pel fusion pressures were maintained between 80 and 100 mm Hg and betwe en 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 meas ured continuously in each ventricle by means of localized phosphorus 31 mag netic resonance spectroscopy with 2 surface coils. Results: Both antegrade and retrograde continuous normothermic blood cardioplegic perfusion resulte d in a significant increase in inorganic phosphate level and decreases in c reatine 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 sign ificantly lower in the right ventricle than in the left ventricle during re trograde continuous normothermic blood cardioplegic perfusion. On reperfusi on, the inorganic phosphate level, creatine phosphate level, and intracellu lar pH recovered completely; however, no recovery in the adenosine triphosp hate level was seen in the, ventricles of either group. Conclusions: Retrog rade continuous normothermic blood cardioplegic perfusion does not provide better protection to ischemic areas of the ventricles than does antegrade c ontinuous normothermic blood cardioplegic perfusion under our experimental conditions.