Determination of the effect of Inotropic stimulation on regionally ischemic and hypokinetic myocardium is complicated when intravenous administration of the inotropic agent also causes stimulation of nonlschernic adjacent and distant regions, thereby altering global ventricular hemodynamics. To obviate such events, 16 anesthetized swine were studied during regional inotropic stimulation by infusion of dobutamine hydrochloride (2.5±1 μg/min) into the cannulated left anterior descending coronary artery. Coronary inflow was controlled by a pump in an extracorporeal circuit. Two groups of swine with different degrees of ischemia were studied. In the first group of animals (n=8), reduction in coronary inflow to produce a fall in coronary artery pressure (CAP) from 114±7 mm Hg to 62±2 mm Hg caused a decrease in percent systolic wall tinckening (percent;WTh) from 34.6±8.1percent; to 25.4±5.8percent; (p<0.005). In the second group of animals (n=8), CAP was decreased to 46±5 mm Hg (control: 115±8 mm Hg) and percent;WTh decreased from 34.1±16.4percent; to 10.4±6.9percent; (p<0.001). Subendocardial blood flow was reduced from 1.41 ±0.38 ml/min/g to 0.65±0.13 ml/min/g (group 1, p<0.001) and from 1.08±0.22 ml/min/g to 0.24±0.08 ml/min/g (group 2, p<0.001). Regional infusion of dobutamine caused asynchronous ventricular contraction with early systolic augmentation in wall tinckening followed by late systolic thinning. Therefore, during hypoperfusion regional myocardial function assessed by percent;WTh remained unchanged (26.2±5.8percent;, p=NS) in group 1 and decreased significantly to 1.6±5.1percent; (p<0.041) in group 2. Subendocardial blood flow decreased to 0.44±0.15 ml/min/g in group 1 (p<0.005) and to 0.15±0.07 ml/min/g in group 2 (p<0.012). To account for the augmented early systolic thickening that occurred during asynchronous contraction, a myocardial work index was developed in which the sum of the instantaneous left ventricular pressure-wall tinckness product was calculated for estimation of regional myocardial work. Increases in this work Index were apparent with the addition of dobutamine at both levels of hypoperfusion. This significant enhancement in regional myocardial function in group 2 caused a significant increase of 16percent; (p<0.009) in overall left ventricular power during ejection. Thus, regional inotropic stimulation with dobutamine caused enhancement of maximum work of the ischemic myocardium in the steady state despite a further decrease in subendocardial blood flow.