Effect of β-blockade on dobutamine stress echocardiography

Dobutamine is an effective pharmacologic stress used in conjunction with echocardiography because of its β-agonist properties. Concurrent β-blockade might after this effectiveness; however, current clinical experience has been variable. The purpose of this study is to determine whether concurrent β-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 β-blockade (esmolol 500 μg/kg initial bolus, 100 μg/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 β-blockade resulted in (1) a delayed and diminished increase in hemodynamic parameters (peak heart rate 164.1 ± 22.3 without β-blockade vs 110.1 ± 28.9 beats/min with β-blockade, p < 0.001, and peak systolic blood pressure 137.9 ± 26.8 mm Hg without β-blockade vs 107.3 ± 15.3 mm Hg with β-blockade, P = 0.01), (2) an elimination of the physiologic effects of low-dose (5 and 10 μg/kg/min) dobutamine (−0.7% ± 16.7% change in myocardial thickening from baseline with β-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 β-blockade vs 15.6 ± 6.1 μg/kg/min without β-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 β-blockers and to establish protocol standards are necessary.