© 1993 by European Society of Cardiology
Copyright © 1993, European Society of Cardiology
Hypoperfusion of the myocardium relative to myocardial metabolism during delayed coronary constriction
Department of Pharmacology, Georgetown University School of Medicine, 3900 Reservoir Road NW, Washington DC 20007, USA: A H Huang, B D Nearing, R L Verrier.
Correspondence to Professor Verrier.
Objective: The aim was to test the hypothesis that the myocardium becomes hypoperfused, relative to its metabolic demands, during the delayed coronary constriction which is observed following termination of a period of sympathetic stimulation. Methods: This was tested by beat by beat analysis of the ratio of coronary blood flow to the product of heart rate and systolic blood pressure (HRxSBP), an index of myocardial metabolism, in acutely instrumented open chest canine preparations, before, during, and after direct electrical stimulation of the left stellate ganglion. Results: Myocardial metabolism increased in response to stellate stimulation, as evidenced by increases in heart rate, aortic blood pressure, and HRxSBP. These were accompanied by increased blood flow and decreased vascular resistance in the left anterior descending coronary artery. Delayed coronary constriction, defined as the period with the lowest coronary blood flow observed after the end of the stimulation, occurred 1 to 3 min after stimulation was terminated and was characterised by recovery of heart rate, blood pressure, HRxSBP, and coronary blood flow toward control levels, while coronary vascular resistance overshot to above control levels. The ratio of coronary blood flow to HRxSBP fell progressively in the poststimulation period to significantly less (mean 0.715, range of ± 1 SEM 0.638 to 0.800, p<0.05) than control (1.0, by definition) in experiments performed with partial prestenosis of the left anterior descending coronary artery. In a selected subgroup of observations with a mean reduction in coronary blood flow during delayed coronary constriction comparable to that reported previously, the flow/metabolism ratio was even lower (mean 0.239, range of ± 1 SEM 0.202 to 0.284). Conclusions: The phenomenon of delayed coronary constriction clearly involves a mismatch between myocardial supply and demand: coronary blood flow becomes inappropriately low for the prevailing level of myocardial metabolism.
Cardiovascular Research 1993;27:435-441
KEYWORDS coronary; stenosis; delayed vasoconstriction; myocardial metabolism; stress
Supported by grant HL-33567 from the US National Heart, Lung and Blood Institute, National Institutes of Health. AHH and BDN are recipients of postdoctoral fellowships from The American Heart Association, Nation's Capital Affiliate. We sincerely thank Ms Marian Thurnher for her excellent technical assistance in the execution of these experiments, Dr Mirza Ali for his carefully considered advice on the statistical analyses applied, and Mrs Sandra S Verrier for her expert assistance in editing this manuscript and preparing the figures.