Arbutamine stimulation detects viable myocardium 4 weeks after coronary occlusion

At low doses, dobutamine has potent inotropic, but limited chronotropic, ef fects-properties that may be necessary for detection of hibernating myocard ium. The efficacy of other catecholamines, which have more closely coupled inotropic and chronotropic effects, for the detection of viable myocardium is unknown. This study evaluated the efficacy of arbutamine, a catecholamin e with potent throne-tropic effects, for the detection of viable myocardium in a canine model of hibernating myocardium. Contractile reserve was asses sed during stepwise arbutamine infusion (dosages of 2.5, 5, 10, 50, and 100 ng/kg/min) at 3 days (early) and 4 weeks (late) after coronary Ligation. S egment shortening, wall thickening, and segmental wall motion were assessed by sonomicrometry and echocardiography. After 4 weeks of occlusion, functi onal recovery was assessed after revascularization During the early arbutam ine study, the sensitivity for predicting functional recovery was highest a t a dosage of 50 ng/kg/min, which also produced tathycardia. The sensitivit y was 50% for segment shortening, 20% for wall thickening and 75% for wall motion score: The late arbutamine study had improved sensitivity. The sensi tivity was 100% for segment shortening, 80% for wall thickening, and 90% fo r wall motion score at a dosage of 50 ng/kg/min. At the late arbutamine stu dy, myocardial perfusion reserve in the ischemic zone of dogs with function al recovery was only mildly reduced (2.0 versus 2.6 in nonischemic zones, P = .53). After coronary occlusion, viable myocardium can be detected with h igh doses of arbutamine that produce tachycardia. However, the sensitivity of arbutamine stimulation for predicting functional recovery is low early a fter occlusion, but it is improved by 4 weeks after occlusion with adequate perfusion reserve.