Uniformity of perfusion in all regions of the human heart by warm continuous retrograde cardioplegia

Background. Animal models have suggested that retrograde cardioplegia may be poorly distributed to septal and right ventricular regions of the heart; if true, this may have dangerous implications for warm continuous retrograde cardioplegia in humans. We have previously shown that blood gases from coronary arteries during warm continuous retrograde cardioplegia represent postcapillary ''venous'' gases and are reflective of myocardial perfusion. Methods. To determine regional differences in perfusion during warm continuous retrograde cardioplegia we obtained blood gases from three regions of the heart in 141 consecutive patients undergoing coronary artery by-pass grafting, aortic valve replacement, or both. Right heart perfusion was determined by blood gases from the right coronary artery orifice, acute marginal, or posterior descending coronary arteries; circumflex or lateral wall perfusion was determined by samples from obtuse marginal or intermediate coronary arteries; and anterior wall/septal perfusion was determined by left anterior descending and diagonal coronary artery blood gases. Warm continuous retrograde cardioplegia flow ranged from 150 to 300 ml/min depending on heart size. A mean of 4 +/- 1 samples/patient were obtained. Results. There were no regional differences in postcapillary pH, carbon dioxide tension, or CO2 production during warm continuous retrograde cardioplegia. Oxygen tensions were lower in the right and anterior/septal regions of the heart, implying more O-2 uptake. No regional acidosis, consistent with poor perfusion, could be detected. Conclusions. We conclude that, unlike experimental models,regional myocardial perfusion, including the right heart, is uniform during ''high-flow'' warm continuous retrograde cardioplegia in humans.