Affiliation:
1. Department of Thoracic and Cardiovascular Surgery, University Hospital in Tromsø, N-9038 Tromsø, Norway
Abstract
The myocardial oxygen consumption (MV˙o 2) to left ventricular pressure-volume area (PVA) relationship is assumed unaltered by substrates, despite varying phosphate-to-oxygen ratios and possible excess MV˙o 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. MV˙o 2 was calculated from coronary flow and arterial-coronary sinus O2 differences. Metabolism was altered by glucose-insulin-potassium (GIK) or Intralipid-heparin (IH) infusions in random order and monitored with [14C]glucose and [3H]oleate tracers. Profound shifts in glucose and fatty acid oxidation were observed. Contractility, coronary flow, and slope of the MV˙o 2-PVA relationship were unchanged during GIK and IH infusions. MV˙o 2 at zero PVA (unloaded MV˙o 2) was 0.16 ± 0.13 J ⋅ beat− 1 ⋅ 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 MV˙o 2-PVA relationship. This may in part explain the “oxygen-wasting” effect of lipid-enhancing interventions such as adrenergic drugs and ischemia.
Publisher
American Physiological Society
Subject
Physiology (medical),Cardiology and Cardiovascular Medicine,Physiology
Cited by
223 articles.
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