title: Oxygen-wasting effect of inotropy in the "virtual work model".
abstract: In the "virtual work model," left ventricular total mechanical energy (TME) is linearly related to myocardial oxygen consumption (MVO2). This relationship (MVO2-TME) is supposedly independent of inotropic stimulation, vascular loading, and heart rate variations. We reexamined the effect of inotropic stimulation (dopamine) on the metabolic to mechanical energy transfer in nine open-chest anesthetized pigs. Left ventricular mechanical energy was calculated using TME (mean ejection pressure x end-diastolic volume + stroke work), TMEW (end-diastolic volume reduced by unstressed ventricular volume), and the pressure-volume area (PVA). A highly linear relationship between MVO2 and mechanical energy was found for all three indexes during control and dopamine runs (r = 0.87-0.99). The slopes were unaltered by dopamine. y-Axis intercepts were (control vs. dopamine) as follows (in J. beat-1. 100 mg-1; means +/- SD): TME, 0.36 +/- 0.12 vs. 0.61 +/- 0.30 (P < 0.02); TMEW, 0.43 +/- 0.16 vs. 0.72 +/- 0.32 (P < 0.02); and PVA, 0.34 +/- 0.13 vs. 0.60 +/- 0.30 (P < 0.02). We conclude that the virtual work model is dependent on inotropic stimulation and that new insight into myocardial chemomechanical coupling is not added by this concept.
authors: Department of Thoracic and Cardiovascular Surgery, University Hospital of Tromso, N-9038 Tromso, Norway. korvald@fagmed.uit.no
authors: C
authors: C
authors: Korvald
authors: O P
authors: OP
authors: Elvenes
authors: L M
authors: LM
authors: Ytrebø
authors: D G
authors: DG
authors: Sørlie
authors: T
authors: T
authors: Myrmel
mesh_terms: D000818:Animals; D002316:Cardiotonic Agents / Q000494:pharmacology; D004298:Dopamine / Q000494:pharmacology; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology*; D005260:Female; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology; D008297:Male; D008955:Models, Cardiovascular; D009200:Myocardial Contraction / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D013552:Swine; D016277:Ventricular Function, Left / Q000187:drug effects / Q000502:physiology*
chemical_list: D002316:Cardiotonic Agents; D004298:Dopamine