MYOCARDIAL CIRCULATORY AND METABOLIC EFFECTS OF ATRIAL-NATRIURETIC-PEPTIDE AFTER CORONARY-ARTERY BYPASS-GRAFTING

The purpose of this study was to examine the effects of incremental in fusion rates of human atrial natriuretic peptide (ANP), 25, 50, 100 ng . kg(-1). min(-1), on myocardial blood flow and metabolism (n=10), an d to compare the effects of ANP on these variables with those of equip otent infusion rates of sodium nitroprusside (SNP) (n=9) 1-3 h after c oronary artery bypass grafting (CABG). ANP induced a dose-dependent de crease in mean arterial blood pressure and systemic vascular resistanc e. There were no changes in cardiac index, heart rate, or cardiac fill ing pressures. ANP caused no changes in myocardial blood flow or its d istribution, and caused no changes in myocardial oxygen extraction. Re gional myocardial lactate uptake (RMLU) and extraction (RMLE) increase d significantly (P <0.05) at 50 ng . kg(-1). min(-1) (10.2+/-3.8 mu mo l/min and 8.2%+/-3.0%, respectively) as compared to control (-1.1+/-3. 0 mu mol/min and -1.3%+/-3.3%, respectively). RMLE and RMLU were signi ficantly (P <0.05) higher with ANP (5.7%+/-2.5% and 6.8+/-3.7 mu mol/m in, respectively) compared to SNP (-1.5%+/-2.1% and -0.1+/-3.7 mu mol/ min, respectively). We conclude that ANP has no dilatory effects on co ronary vascular resistance vessels and thus lacks the potential to mal distribute flow, and that ANP improves myocardial lactate metabolism a fter CABG.