Effect of beta-adrenergic receptor blockade on the physiologic response to dobutamine stress echocardiography.

Dobutamine is an effective pharmacologic stress agent because of its beta-adrenergic receptor agonist properties. Theoretically, concurrent beta-adrenergic receptor blockade might alter this effectiveness, but clinical experience has been variable. Before assessing the relative effectiveness and implications of dobutamine stress echocardiography (DSE) to detect myocardial ischemia in the presence of beta-blockade the physiologic and hemodynamic effects of dobutamine with simultaneous beta-blockade must be understood in a controlled setting. Therefore the purpose of this study was to determine if beta-blocking agents alter the timing and magnitude of the physiologic response to graded doses of dobutamine during a standard DSE. Paired DSEs were performed in seven instrumented open-chest dogs with and without beta-blockade (esmolol 500 micrograms/kg initial bolus and 100 micrograms/kg/min infusion). Heart rate, systolic pressure, proximal left anterior descending coronary artery flow, myocardial thickening, and percentage left ventricular area change (% AC) were monitored. The data for each parameter were fit to linear or exponential functions. With graded doses of dobutamine, the rate of increase in coronary flow was greater than that in %AC, which in turn was greater than that in heart rate (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)