The Annals of Thoracic Surgery, Vol 52, 750-758, Copyright © 1991 by The Society of Thoracic Surgeons
Inotropic stimulation and oxygen consumption in a canine model of dilated cardiomyopathy
CM Dyke, KF Lee, J Parmar, RJ Dignan, T Yeh Jr, A Abd-Elfattah and AS Wechsler
Department of Surgery, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298.
Inotropic support for the dilated, failing ventricle results in complex
hemodynamic changes affecting preload, afterload, contractility, and heart
rate, each of which affects myocardial oxygen consumption. Appreciation of
a hierarchy of hemodynamic determinants of myocardial oxygen consumption
may be helpful to the clinician trying to balance oxygen demands and
hemodynamic performance. We tested the hypothesis that epinephrine alters
the hierarchy of hemodynamic determinants of myocardial oxygen consumption
in a canine model of dilated cardiomyopathy created by rapid ventricular
pacing. Dogs (n = 10) were instrumented to record left ventricular pressure
and dimension, and a modified right heart bypass preparation was used to
control left ventricular workload. Coronary sinus effluent was
quantitatively collected and analyzed for oxygen content and used to
calculate myocardial oxygen consumption. Epinephrine administration
significantly increased myocardial oxygen consumption in the empty, beating
heart; however, when the relationships of multiple determinants of left
ventricular work and load were compared before and after epinephrine
administration, no oxygen wasting effect was observed. Using multivariate
linear regression analysis, a hierarchy of hemodynamic determinants of
myocardial oxygen consumption was created. In the untreated heart, stroke
work and cardiac output were the primary hemodynamic determinants of oxygen
consumption; epinephrine significantly altered the determinants such that
wall stress became the dominant hemodynamic determinant of myocardial
oxygen consumption. Focused manipulation of wall stress in the treated,
failing heart may limit the potentially deleterious effects of inotropic
stimulation in this setting.