Arbutamine is a new
catecholamine designed for use as a pharmacologic stress agent. This study compared the sensitivity of
arbutamine with symptom-limited exercise to induce echocardiographic signs of
ischemia.
Arbutamine was administered by a computerized closed-loop delivery system that controls the infusion rate of
arbutamine toward a predefined rate of heart rate increase and maximum heart rate limit. Beta blockers were stopped > or = 48 hours before both tests. Stress was stopped for intolerable symptoms, or clinical, electrocardiographic or echocardiographic signs of
ischemia (new or worsening wall motion abnormality), target heart rate (> or = 85% age predicted maximum heart rate), or plateau of heart rate response. Thirty-seven patients were entered into the study (35
arbutamine and exercise, 1
arbutamine only, 1 exercise only), of which 30 had angiographic evidence of
coronary artery disease (> or = 50% lumen diameter narrowing). Rate-pressure product increased significantly in response to both stress modalities (p < 0.001) and was significantly greater with exercise (11,308 +/- 2,443) than with
arbutamine (9,486 +/- 2,479, p < 0.001). The time to maximum heart rate was longer during
arbutamine stress echocardiography than during exercise testing (17.3 +/- 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 ischemia was 94% (95% confidence interval 70% to 100%) and 88% (95% confidence interval 62% to 98%), respectively. The most frequent adverse events during
arbutamine (n = 36) were
dyspnea (5.6%) and
tremor (5.6%). Two
arbutamine stress tests were discontinued due to arrhythmias: 1 patient had premature atrial and ventricular beats, and the other had
premature atrial contractions and
atrial fibrillation. Arrhythmias were well tolerated and resolved without sequelae. In conclusion, the sensitivity of
arbutamine to induce echocardiographic signs of
ischemia was similar to that of exercise despite a lower rate-pressure product.
Arbutamine was well tolerated and provides a reliable alternative to exercise echocardiography.