Divergent Effects of Inotropic Stimulation

Mechanical function remains depressed for hours and days after even brief periods of ischemia. To determine whether the depressed function of the reperfused myocardium could be improved by inotropic stimulation, we studied segmental function during ischemia and after reperfusion using mercury-in-Silastic length gauges in 15 dogs. During coronary artery occlusion, segmental function could not be improved by inotropic stimulation with dopamine. Release of occlusion after 30 minutes of ischemia resulted in only slight improvement in segmental function (systolic shortening at 20% of control). After reperfusion, segmental function could be markedly enhanced by inotropic stimulation. The response to inotropic stimulation was similar after reperfusion after 3 hours of ischemia if the myocardium remained viable (nine dogs). When the myocardium was necrotic (five dogs), there was no improvement after reperfusion, either spontaneously or in response to inotropic stimulation. If applicable to humans, these results suggest that intractable pump failure caused by extensive but reversible ischemia could be effectively treated by reperfusion and inotropic stimulation.