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Am J Physiol Heart Circ Physiol. 2000 Apr;278(4):H1345-51.

Myocardial substrate metabolism influences left ventricular energetics in vivo.

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1
Department of Thoracic and Cardiovascular Surgery, University Hospital in Tromsø, N-9038 Tromsø, Norway. korvald@fagmed.uit.no

Abstract

The myocardial oxygen consumption (MVO(2)) to left ventricular pressure-volume area (PVA) relationship is assumed unaltered by substrates, despite varying phosphate-to-oxygen ratios and possible excess MVO(2) associated with fatty acid consumption. The validity of this assumption was tested in vivo. Left ventricular volumes and pressures were assessed with a combined conductance-pressure catheter in eight anesthetized pigs. MVO(2) was calculated from coronary flow and arterial-coronary sinus O(2) differences. Metabolism was altered by glucose-insulin-potassium (GIK) or Intralipid-heparin (IH) infusions in random order and monitored with [(14)C]glucose and [(3)H]oleate tracers. Profound shifts in glucose and fatty acid oxidation were observed. Contractility, coronary flow, and slope of the MVO(2)-PVA relationship were unchanged during GIK and IH infusions. MVO(2) at zero PVA (unloaded MVO(2)) was 0.16 +/- 0.13 J x beat(-1) x 100 g(-1) higher during IH compared with GIK infusion (P = 0.001), a 48% increase. The study demonstrates a marked energetic advantage of glucose oxidation in the myocardium, profoundly affecting the MVO(2)-PVA relationship. This may in part explain the "oxygen-wasting" effect of lipid-enhancing interventions such as adrenergic drugs and ischemia.

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