MYOCARDIAL-FUNCTION AND METABOLISM IN PIG HEARTS AFTER RELIEF FROM CHRONIC PARTIAL CORONARY STENOSIS

Metabolic behavior was compared during acute extracorporeal reperfusio n after removal of a chronic 4-day partial coronary stenosis in eight pig hearts (RCS group) and during comparable extracorporeal perfusion in seven chronically prepared hearts (Sham group). Coronary stenosis i n RCS hearts was induced in the left anterior descending (LAD) artery by partial inflation of a hydraulic occluder to restrict LAD peak phas ic velocity by similar to 50%. Regional mechanical shortening was decr eased in RCS compared with Sham hearts after 4 days of chronic coronar y stenosis [diminished systolic shortening (P < 0.066) with systolic e xpansion (P < 0.015)] but was comparable to Sham hearts after relief f rom stenosis. At analogous workloads (left ventricular pressure and he art rate) during reperfusion, metabolic behavior was distinctive betwe en groups. Specifically, compared with Sham hearts, myocardial O-2 con sumption was selectively increased in RCS hearts (+49 Delta%, P < 0.02 6) as was fatty acid oxidation estimated from (CO2)-C-14 production fr om [U-C-14]palmitate (+60 Delta%, P < 0.061) and exogenous glucose uti lization measured from the release of (H2O)-H-3 from [5-H-3]glucose (517 Delta%, P < 0.025). At the conclusion of the studies, triphenyltet razolium chloride staining showed no gross evidence of macroinfarction in RCS or Sham hearts, and there was an essentially unremarkable hist ological survey of anterior myocardium for microscopic necrosis in eit her group. The level of O-2 consumption and preservation of preferred fatty acid utilization indicate that metabolism remains or regains its aerobic pattern of activity in early recovery immediately after remov al of chronic partial coronary stenosis. The increase in use of glucos e substrate is of interest and may indicate loss of allosteric regulat ion by fatty acids or its intermediates upon rate-limiting enzymes in the glycolytic cascade.