Effect of beta-blockade on dobutamine stress echocardiography.

Dobutamine is an effective pharmacologic stress used in conjunction with echocardiography because of its beta-agonist properties. Concurrent beta-blockade might alter this effectiveness; however, current clinical experience has been variable. The purpose of this study is to determine whether concurrent beta-blockade alters the ability of a dobutamine stress echocardiogram to detect a fixed coronary stenosis by preventing the onset of a wall motion abnormality or by altering the dose at which the wall motion abnormality appears. Paired dobutamine stress tests with and without beta-blockade (esmolol 500 microgram/kg initial bolus, 100 microg/kg/min infusion) were performed in a canine model (n = 8) with a fixed single-vessel coronary stenosis. Heart rate, systolic pressure, proximal left anterior descending coronary flow, myocardial thickening (by sonomicrometry), and left ventricular area change (by epicardial echocardiography) were monitored. Simultaneous beta-blockade resulted in (1) a delayed and diminished increase in hemodynamic parameters (peak heart rate 164.1 +/- 22.3 without beta-blockade vs 110.1 +/- 28.9 beats/min with beta-blockade, p < 0.001, and peak systolic blood pressure 137.9 +/- 26.8 mm Hg without beta-blockade vs 107.3 +/- 15.3 mm Hg with beta-blockade, p = 0.01), (2) an elimination of the physiologic effects of low-dose (5 and 10 microg/kg/min) dobutamine (-0.7 percent +/- 16.7 percent change in myocardial thickening from baseline with beta-blockade, p = NS), and (3) an elimination or alteration in timing of inducible wall motion abnormalities caused by severe coronary artery stenoses (mean termination dose 28.8 +/- 9.9 with beta-blockade vs 15.6 +/- 6.1 microg/kg/min without beta-blocker, p < 0.01). The findings in this canine model suggest that the competitive antagonist markedly attenuates the ability of dobutamine stress echocardiography to detect a significant coronary lesion and may alter its ability to detect viable myocardium at low-dose testing. Further clinical studies to determine the sensitivity of dobutamine stress echocardiography in the presence of beta-blockers and to establish protocol standards are necessary.