ADEQUACY OF LOW-STRESS ARBUTAMINE TO PROVOKE MYOCARDIAL-ISCHEMIA DURING ECHOCARDIOGRAPHY

Arbutamine is a new, potent, short-acting synthetic catecholamine developed specifically for use as a cardiac stress agent, Previous reports on the accuracy of arbutamine fbr the detection of coronary artery disease have relied on heart rate (HR) increases similar to those seen at peak exercise, This study was undertaken to test the potential to provoke ischemic wall motion abnormalities on echocardiography using arbutamine at a HR below that associated with peak exercise, One hundred forty-six patients with coronary artery disease underwent computerized closed-loop stress testing with arbutamine 120 (82%) had echocardiographic images adequate for analysis at baseline, low stress (20 beats/min above baseline), and peak stress (target of 85% age-predicted peak HR). Ejection fraction increased from 59 +/- 10% at baseline to 72 +/- 12% at low stress, and remained stable at 72 +/- 14% at peak stress, Of 88 patients with echocardiographic evidence of ischemia at peak stress, 73 (83%) had evidence of ischemia at low stress. Change in wall motion score index from baseline to low stress represented 62% of the change noted from baseline to peak stress, A greater number of stenotic vessels were associated with a somewhat higher proportion of ischemic responses evident at low stress, The present study suggests that the maximal inotropic effects of arbutamine may occur at a dose lower than that required for maximal chronotropic effect, In the future, it may be possible to establish an infusion end point for arbutamine stress testing using a HR <85% of the age-predicted maximum.