COMPARISON OF ARBUTAMINE AND EXERCISE ECHOCARDIOGRAPHY IN DIAGNOSING MYOCARDIAL-ISCHEMIA

Arbutamine is a new catecholamine designed for use as a pharmacologic stress agent. This study compared the sensitivity of arbutamine with s ymptom-limited exercise to induce echocardiographic signs of ischemia. Arbutamine was administered by a computerized closed-loop delivery sy stem that controls the infusion rate of arbutamine toward a predefined rate of heart rate increase and maximum heart rate limit. Beta blocke rs were stopped greater than or equal to 48 hours before both tests. S tress was stopped for intolerable symptoms, or clinical, electrocardio graphic or echocardiographic signs of ischemia (new or worsening wall motion abnormality), target heart rate (greater than or equal to 85% a ge predicted maximum heart rate), or plateau of heart rate response. T hirty-seven patients were entered into the study (35 arbutamine and ex ercise, 1 arbutamine only, 1 exercise only), of which 30 had angiograp hic evidence of coronary artery disease (greater than or equal to 50% lumen diameter narrowing). Rate-pressure product increased significant ly in response to both stress modalities (p <0.001) and was significan tly greater with exercise (11,308 +/- 2,443) than with arbutamine (9,4 86 +/- 2,479, p <0.001). The time to maximum heart rate was longer dur ing arbutamine stress echocardiography than during exercise testing (1 7.3 +/- 9.4 versus 9.3 +/- 4.2 minutes, respectively, p <0.001). There were more patients with interpretable echo data for arbutamine (82%) than for exercise (67%). Sensitivity for recognition of myocardial isc hemia was 94% (95% confidence interval 70% to 100%) and 88% (95% confi dence interval 62% to 98%), respectively. The most frequent adverse ev ents during arbutamine (n = 36) were dyspnea (5.6%) and tremor (5.6%). Two arbutamine stress tests were discontinued due to arrhythmias: 1 p atient had premature atrial and ventricular beats, and the other had p remature atrial contractions and atrial fibrillation. Arrhythmias were well tolerated and resolved without sequelae. In conclusion, the sens itivity of arbutamine to induce echocardiographic signs of ischemia wa s similar to that of exercise despite a lower rate-pressure product. A rbutamine was well tolerated and provides a reliable alternative to ex ercise echocardiography. (C) 1997 by Excerpta Medica, Inc.