Coronary Reserve of High- and Low-Flow Regions in the Dog Heart Left Ventricle

Loncar, Robert MD
Flesche, Christian W. MD
Deussen, Andreas MD

Received September 12, 1997; revision received January 27, 1998; accepted February 4, 1998.
From the Institut fur Herz- und Kreislaufphysiologie (R.L.) and the Institut fur Klinische Anasthesiologie (C.W.F.), Heinrich-Heine-Universitat Dusseldorf, and the Institut fur Physiologie, Medizinische Fakultat Carl Gustav Carus der Technischen Universitat Dresden (A.D.), Germany.
Correspondence to Dr Andreas Deussen, Professor and Chairman, Institut fur Physiologie, Medizinische Fakultat Carl Gustav Carus der Technischen Universitat Dresden, Fetscherstr 74, D-01307 Dresden, Germany.

Circulation 98(3):p 262-270, July 21, 1998.

Background

Left ventricular myocardial blood flow is spatially heterogeneous. The hypothesis we tested was whether myocardial areas with a steady-state flow <0.5 times mean flow are underperfused and areas with flow >1.5 times mean flow are overperfused.

Methods and Results-In anesthetized beagle dogs (n=10), the relationship between local blood flow versus S-adenosylhomocysteine (SAH) concentration, a measure of the free intracellular adenosine concentration, and lactate, a measure of the myocardial NADH/NAD⁺ ratio, were determined under control conditions and after coronary constriction. Control local myocardial blood flow was 0.99 +/- 0.46 mL [middle dot] min^-1 [middle dot] g^-1, with a coefficient of variation of 0.36 +/- 0.12 (n=256 per heart; sample wet mass, 125 +/- 30 mg). Tissue concentrations of SAH (3.4 +/- 2.5 nmol/g) and lactate (1.88 +/- 0.80 [micro sign]mol/g) were not elevated in low-flow samples. However, after coronary artery constriction, poststenotic blood flow decreased from 1.00 +/- 0.27 to 0.49 +/- 0.22 mL [middle dot] min^-1 [middle dot] g^-1 (P<0.04), with significant correlation between local SAH and flow (r=-0.59) and lactate and flow (r=-0.50). Although nearly all samples from control high-flow regions showed increased SAH concentrations if relative flow after stenosis was <1.0, control low-flow samples frequently displayed low SAH concentrations. The percent reduction in flow determined the changes in the local SAH and lactate concentration, independent of the local control blood flow.

Conclusions

When the coronary inflow is unrestricted, the oxygen supply to control low-flow regions meets metabolic demand. Flow to control high-flow regions reflects a higher local demand rather than overperfusion. Thus, blood flow heterogeneity most likely reflects differences in aerobic metabolism. (Circulation. 1998;98:262-270.)