The Effect of Inotropic Agent, Dobutamine, on Ventriculoarterial Coupling and Work Efficiency in Acute Regional Ischemia

Background. The left ventriculoarterial (V-A) coupling and work efficiency have been studied experimentally in normal heart and clinically in patients with congestive heart failure. However, few studies have been done experimentally about the V-A coupling and work efficiency in the diseased heart. In the present study, therefore, we investigated the effect of dobutamine on left V-A coupling and work efficency in acute regional myocardial ischemia. Methods and Results. We obtained the end-systolic pressure volume relation (ESPVR) using conductance catheter with high fidelity micromanometer in 13 open-chest anesthetized dogs. Data were obained at baseline, ischemia induced by left anterior descending coronary artery occlusion, low dose (2/μg/kg/min) and high dose (7μg/kg/min) dobutamine infusion under ischemia. Left ventricular contractility was assessed by the slope (Ees) and volume axis intercept (Vo) of ESPVR. The arterial properties were assessed by the effective arterial elastance (Ea), which was expressed by the slope of the end-systolic pressure stroke volume relation. We analyzed V-A coupling (Ea/Ees) and work efficiency, defined as the ratio of external work to pressure-volume area. Ees slightly decreased without significant change and Vo shifted to the right with acute regional myocardial ischemia. Ees increased by dobutamine dose-dependently, however, Vo showed no significant changes. Ea/Ees decreased, while work efficiency increased with myocardial ischemia.With low dose dobutamine, Ea/Ees and work efficiency returned to the control value. High dose dobutamine, however, could not make any further changes in both Ea/Ees and work efficiency, compared with those in low dose dobutamine. Conclusion: Low dose dobutamine might be sufficiently enough for the purpose of achieving the optimal ventriculoarterial coupling in acute regional ischemia with mismatched ventriculoarterial coupling and depressed LV work efficiency.

Emax

Ventribuloarterial Coupling

Work Effiiciency