Enoximone coupled to very low dose dobutamine echocardiography detects myocardial viability in akinetic and dyskinetic post-myocardial infarcted areas

Abstract

Dobutamine and enoximone stimulate independently inotropic reserve by increasing intracellular cyclic adenosine monophosphate. The potential of enoximone (0.75 mg/kg body weight over 10 minutes) followed by very low dose (2.5 μg/kg/min) dobutamine echocardiography to predict recovery of ventricular function in akinetic and dyskinetic postinfarcted areas was studied. We enrolled 22 patients with previous Q-wave myocardial infarction and regional wall motion abnormalities related to left anterior descending arterial disease, left ventricular ejection fraction <40%, and all scheduled for myocardial revascularization. A 10 μg/kg/min dobutamine test was performed 48 hours before the study protocol. Test images obtained at peak of pharmacodynamic effects were compared with those obtained at 4 months after myocardial revascularization. We used a 16-segment ventricular model and a 5-grade scoring system. Resting regional myocardial dysfunction graded ≥2 was present in 267 of 352 segments evaluated. Contractile reserve (decrease in resting wall motion score ≥2 grades) at peak effect of enoximone infusion was present in 34 of 112 severely hypokinetic, 42 of 117 akinetic, and 14 of 38 dyskinetic segments. The inotropic reserve evaluated after very low dose dobutamine was observed in 34 of 112 severely hypokinetic, 49 of 117 akinetic, and 20 of 38 dyskinetic segments. After revascularization, recovery of function was observed in 31 of 112 severely hypokinetic, 49 of 117 akinetic, and 21 of 38 dyskinetic segments. Overall, there was a significant correlation between absolute score changes of segments which were abnormal at baseline (n = 267) to enoximone peak effects (r = 0.49, p <0.001) to predict absolute changes after revascularization; after dobutamine there was progress toward identity (r = 0.62, p <0.001) and the difference was significant among correlation slopes of dobutamine alone, enoximone alone, and enoximone plus very low dose dobutamine echocardiograophy (0.45 ± 0.04, 0.51 ± 0.04, and 0.63 ± 0.04, respectively, F = 5.25, p = 0.005). Therefore, enoximone followed by very low dose dobutamine may assess myocardial viability of postinfarcted akinetic and dyskinetic areas. This test may be useful when evaluating patients with more severe cardiac failure and/or life-threatening arrhythmias.