Effects of dobutamine on coronary stenosis physiology and morphology - Comparison with intracoronary adenosine

Background-The mechanisms leading to dobutamine-induced ischemia are not fu lly understood. In the present study, we investigated the effects of high-d ose intravenous dobutamine on morphological and physiological indexes of co ronary stenoses. Methods and Results-Twenty-two patients with normal left ventricular functi on and isolated coronary stenoses were studied. At catheterization, mean ao rtic pressure (P-a), mean distal coronary pressure (Pd), and P-d/P-a as an index of myocardial resistance were recorded at rest, after intracoronary a denosine, and during intravenous infusion of dobutamine (10 to 40 mu g . kg (-1) . min(-1)). Reference vessel diameter and minimal luminal diameter, as assessed by coronary angiography, did not change during dobutamine infusio n compared with baseline (2.84+/-0.49 versus 2.77+/-0.41 mm and 1.35+/-0.38 versus 1.27+/-0.31 mm, respectively; both P=NS). During peak dobutamine in fusion, P-d and P-d/P-a reached similar levels as during adenosine infusion (60+/-18 versus 59+/-18 mm Hg and 0.68+/-0.18 versus 0.68 +/- 0.17, respec tively; all P=NS). In 9 patients, an additional bolus of intracoronary aden osine given at the peak dose of dobutamine failed to further decrease P-d/P -a. Furthermore, in patients with dobutamine-induced wall motion abnormalit ies, the maximal decrease in P-d/P-a was similar during dobutamine and aden osine infusions. Conclusions-High-dose intravenous infusion of dobutamine does not modify th e dimensions of the epicardial coronary stenosis. However, much like the di rect coronary vasodilator adenosine, dobutamine fully exhausts myocardial r esistance regardless of the presence of mechanical dysfunction.