Effect of coronary artery bypass surgery on myocardial perfusion and ejection fraction response to inotropic stimulation in patients without improvement in resting ejection fraction

The aim of this study was to assess the effect of coronary artery bypass gr afting (CABG) on myocardial perfusion and left ventricular (LV) contractile reserve in patients with reduced ejection fraction (EF). We studied 57 pat ients (age 59 +/- 8 years, 46 men and 11 women) with EF less than or equal to 40% referred for CABG with dobutamine (up to 40 mu g/kg/min) stress-rein jection thallium-201 single-photon emission computed tomography, and radion uclide ventriculography at rest and at low-dose dobutamine before and 3 mon ths after CABG. An increase in resting EF greater than or equal to 5% occur red in 12 patients (group A) after CABG (EF 34% before and 46% after CABG), whereas no increase occurred in the remaining 45 patients (group B) (EF 34 % before and 32% after CABG). A significant increase in EF from rest to tow -dose dobutamine radionoclide ventriculography occurred before and after CA BG, The magnitude of increase was more significant after than before CABG i n group A (12% vs 7%) as well as in group B (13% vs 7%, both p <0.001). Pat ients in both groups had a significant reduction in stress, rest, and ische mic perfusion scores after CABG, However, the percentage of reduction in re sting perfusion defect score was more significant in group A than in group B (60% vs 30%, respectively, p <0.01), It is concluded that CABG induces a significant improvement in resting myocardial perfusion and EF response to inotropic stimulation, even in the absence of improved Ef: at rest, Patient s without improvement in resting EF after CABG have mild improvement in res ting myocardial perfusion that may be sufficient to increase EF after CABG during inotropic stimulation, but nor at rest. We describe the myocardium w ith these characteristics as "the reactive myocardium." (C) 2000 by Excerpt a Medica Inc.