ASSESSMENT OF RETROGRADE CARDIOPLEGIA WITH MAGNETIC-RESONANCE-IMAGINGAND LOCALIZED P-31 SPECTROSCOPY IN ISOLATED PIG HEARTS

Objective: This study was done to determine whether retrograde deliver y of cardioplegic solution provides uniform blood flow to the myocardi um supplied by an occluded coronary artery and whether it maintains my ocardial energy levels beyond the coronary occlusion, Methods: Isolate d pig hearts were used, A hydraulic occluder was placed at the origin of the left anterior descending coronary artery, The perfusion pressur e for retrograde delivery of cardioplegic solution was controlled at 4 0 to 50 mm Hg, Magnetic resonance imaging and localized P-31 magnetic resonance spectroscopy were used to assess myocardial perfusion and en ergy metabolism, respectively, Results: Magnetic resonance perfusion i mages (n = 7) showed that the perfusion defect that occurred during an tegrade delivery of cardioplegic solution (as a result of the occlusio n of the left anterior descending coronary artery) resolved during ret rograde delivery of cardioplegic solution, Retrograde perfusion delive red similar amounts of flow to the jeopardized myocardium as it did to other areas of the myocardium. However, the distribution of cardiople gic solution by the retrograde route was heterogeneous (cloudlike) acr oss both ventricular walls, P-31 magnetic resonance spectra showed tha t the ischemic changes induced by occlusion of the left anterior desce nding artery during antegrade perfusion were greatly alleviated by ret rograde perfusion; however, it took longer for retrograde cardioplegia (n = 7, 17.08 minutes) to restore the levels of inorganic phosphate!p hosphocreatine relative to the effect of releasing the left anterior d escending artery occluder during antegrade delivery of cardioplegic so lution (II = 7, 5.3 minutes), Conclusions: First, retrograde delivery of cardioplegic solution provides sufficient flow to the myocardium be yond a coronary occlusion to maintain near normal levels of energy met abolites, and second, the efficacy of the retrograde route of cardiopl egic solution delivery (in terms of distribution of the solution and r ate of myocardial energy recovery) is significantly lower than that of the antegrade route.