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

Abstract

Background-Left ventricular myocardial blood flow is spatially heterogeneous. The hypothesis we tested was whether myocardial areas with a steady-state flow Ͻ0.5 times mean flow are underperfused and areas with flow Ͼ1.5 times mean flow are overperfused. Methods and Results-In anesthetized beagle dogs (nϭ10), 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 ϩ ratio, were determined under control conditions and after coronary constriction. Control local myocardial blood flow was 0.99Ϯ0.46 mL ⅐ min Ϫ1 ⅐ g Ϫ1 , with a coefficient of variation of 0.36Ϯ0.12 (nϭ256 per heart; sample wet mass, 125Ϯ30 mg). Tissue concentrations of SAH (3.4Ϯ2.5 nmol/g) and lactate (1.88Ϯ0.80 mol/g) were not elevated in low-flow samples. However, after coronary artery constriction, poststenotic blood flow decreased from 1.00Ϯ0.27 to 0.49Ϯ0.22 mL ⅐ min Ϫ1 ⅐ g Ϫ1 (PϽ0.04), with significant correlation between local SAH and flow (rϭϪ0.59) and lactate and flow (rϭϪ0.50). Although nearly all samples from control high-flow regions showed increased SAH concentrations if relative flow after stenosis was Ͻ1.0, 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.)

Fractal regional myocardial blood flows pattern according to metabolism, not vascular anatomy

“…The data do imply that low-flow regions are not metabolically deprived, or deficient in vascularity, for they respond proportionately (or even more) to increases in metabolic demand. This fits, too, with the data of Loncar et al (39) showing that, unless coronary stenosis is induced, there is normal aerobic metabolism (without excess lactate production in lowflow regions). This fits the observation that the coronary flows The nth neighbor correlation coefficients were obtained for individual pieces (OE), pairs of pieces (x), quadruples of pieces (o), and octuplets of pieces (p).…”

Progressively heterogeneous mismatch of regional oxygen delivery to consumption during graded coronary stenosis in pig left ventricle

“…Previous studies showed that regions of high blood flow and metabolic demand, as determined under basal conditions without coronary constriction, are metabolically stressed to a similar extent during hypoperfusion as regions with a low basal blood flow (9,27). Tissue damage following severe ischemia is more frequent in regions with high blood flow under normal conditions (19), which may be related to the higher metabolic rate in these regions.…”

“…The vulnerability of low-vs. high-control blood flow regions has been investigated previously (9,19,27). Here, we plotted oxygen extraction against basal blood flow at t ϭ 0 (Fig.…”

Wieviel Blutfluß braucht das Myokard?

“…Die verwendeten Techniken wurden im Detail beschrieben [2,9,11]. In Kür-ze: Die Untersuchungen wurden an Beaglehunden (14-20 kg) in Nembutal-(50 mg/kg i.v.)…”

“…Niedrigflußareale wurden als Areale definiert, deren Durchblutung kleiner als 50% des Mittelwerts war [9]. Mit diesen wurden …”