Hemodynamic effects of arbutamine

Pharmacological stress agents for evaluation of ischemic heart disease

Ischemic heart disease is the leading cause of death in the developed countries for those older than 65 years of age. In patients suspected to have coronary artery disease a stress test should be performed to identify the vulnerability of the myocardium to ischemia. As a rule of thumb, the evaluation of coronary artery disease is best done by exercise stress test. In patients who are not able to exercise adequately, pharmacological stress agents are used. The commonly used agents are the coronary vasodilators, adenosine and dipyridamole and the catecholamines, dobutamine and arbutamine. These agents are combined with imaging techniques to increase the sensitivity and specificity of the test. These agents have been widely used and have an excellent safety profile. Another advantage in using pharmacological stress agents is that they do not affect the image quality, especially with echocardiography and magnetic resonance imaging. Ongoing developments hold promise for safer and more reliable pharmacological stress agents in the future.

Arbutamine stimulation detects viable myocardium 4 weeks after coronary occlusion

At low doses, dobutamine has potent inotropic, but limited chronotropic, effects-properties that may be necessary for detection of hibernating myocardium. 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 catecholamine with potent chrono-tropic effects, for the detection of viable myocardium in a canine model of hibernating myocardium. Contractile reserve was assessed 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. Segment shortening, wall thickening, and segmental wall motion were assessed by sonomicrometry and echocardiography. After 4 weeks of occlusion, functional recovery was assessed after revascularization. During the early arbutamine study, the sensitivity for predicting functional recovery was highest at a dosage of 50 ng/kg/min, which also produced tachycardia. The sensitivity was 50% for segment shortening, 20% for wall thickening, and 75% for wall motion score. The late arbutamine study had improved sensitivity. The sensitivity was 100% for segment shortening, 80% for wall thickening, and 90% for wall motion score at a dosage of 50 ng/kg/min. At the late arbutamine study, myocardial perfusion reserve in the ischemic zone of dogs with functional recovery was only mildly reduced (2.0 versus 2.6 in nonischemic zones, P =.53). After coronary occlusion, viable myocardium can be detected with high doses of arbutamine that produce tachycardia. However, the sensitivity of arbutamine stimulation for predicting functional recovery is low early after occlusion, but it is improved by 4 weeks after occlusion with adequate perfusion reserve.