Regional sympathetic denervation affects the relation between canine local myocardial blood flow and oxygen consumption

Abstract

Myocardial blood flow and oxygen consumption are heterogeneously distributed. Perfusion and myocardial oxygen consumption are closely correlated in the normal heart. It is unknown how this metabolism-perfusion relation is influenced by sympathetic denervation. We investigated this question in seven chloralose-anaesthetized dogs, 3-4 weeks after regional sympathetic denervation of the left circumflex coronary artery area of supply of the left ventricle. Measurements were made of local myocardial blood flow (MBF, in ml min(-1) (g dry wt)(-1)), measured with microspheres, and myocardial oxygen consumption ( , in mumol min(-1) (g dry wt)(-1)) in the same location, calculated from the (13)C spectrum of tissue extracts after intracoronary infusion of 3-(13)C-lactate. Since both innervated and denervated regions are subject to the same arterial pressure, lower blood flow indicates higher resistance. Mean MBF was 5.56 ml min(-1) (g dry wt)(-1) (heterogeneity of 3.47 ml min(-1) (g dry wt)(-1)) innervated, 7.48 ml min(-1) (g dry wt)(-1) (heterogeneity of 3.62 ml min(-1) (g dry wt)(-1)) denervated (n.s.). Significant linear relations were found between MBF and M Vo2 of individual samples within the innervated and denervated regions. The slopes of these relations were not significantly different, but the adjusted mean was significantly higher in the denervated regions (+1.92 ml min(-1) (g dry wt)(-1), an increase of 38% of the mean MBF at the pooled mean M Vo2, P = 0.028, ANCOVA). The ratio MBF/M Vo2(in ml micromol(-1)) was significantly higher, being 0.296 +/- 0.167 ml micromol(-1) in the denervated region compared with the innervated region, 0.216 +/- 0.126 ml micromol(-1), P = 0.0182, Mann-Whitney U test. These results indicate that sympathetic tone under chloralose anaesthesia imposes a moderate vasoconstrictive effect in the myocardium that is not detected by comparison of the mean blood flow or resistance.