PURPOSE: Functional mitral regurgitation (FMR) and myocardial dyssynchrony commonly occur in patients with dilated cardiomyopathy (DCM). The aim of this study was to elucidate changes in FMR in relation to those in left ventricular (LV) dyssynchrony as well as geometric parameters of the mitral valve (MV) in DCM patients during dobutamine infusion. MATERIALS AND METHODS: Twenty-nine DCM patients (M:F=15:14; age: 62+/-15 yrs) with FMR underwent echocardiography at baseline and during peak dose (30 or 40 ug/min) of dobutamine infusion. Using 2D echocardiography, LV end-diastolic volume, end-systolic volume (LVESV), ejection fraction (EF), and effective regurgitant orifice area (ERO) were estimated. Dyssynchrony indices (DIs), defined as the standard deviation of time interval-to-peak myocardial systolic contraction of eight LV segments, were measured. Using the multi-planar reconstructive mode from commercially available 3D image analysis software, MV tenting area (MVTa) was measured. All geometrical measurements were corrected (c) by the height of each patient. RESULTS: During dobutamine infusion, EF (28+/-8% vs. 39+/-11%, p=0.001) improved along with significant decrease in cLVESV (80.1+/-35.2 mm3/m vs. 60.4+/-31.1 mm3/m, p=0.001); cMVTa (1.28+/-0.48 cm2/m vs. 0.79+/-0.33 cm2/m, p=0.001) was significantly reduced; and DI (1.31+/-0.51 vs. 1.58+/-0.68, p=0.025) showed significant increase. Despite significant deterioration of LV dyssynchrony during dobutamine infusion, ERO (0.16+/-0.09 cm2 vs. 0.09+/-0.08 cm2, p=0.001) significantly improved. On multivariate analysis, DeltacMVTa and DeltaEF were found to be the strongest independent determinants of DeltaERO (R2=0.443, p=0.001). CONCLUSION: Rather than LV dyssynchrony, MV geometry determined by LV geometry and systolic pressure, which represents the MV closing force, may be the primary determinant of MR severity.
Aged ; Dobutamine/administration & dosage/*pharmacology ; Echocardiography ; Female ; Humans ; Male ; Middle Aged ; Mitral Valve/*anatomy & histology/drug effects/*physiopathology ; Mitral Valve Insufficiency/*physiopathology ; Ventricular Dysfunction, Left/*physiopathology

Brief ischemic episodes that induce myocardial and coronary endothelial dysfunction may alter the responses to inotropic drugs. To determine the effects of inotropic drugs in stunned myocardium, the coronary blood flow (CBF), myocardial oxygen consumption (MVO2), and regional mechanical function in response to intracoronary dobutamine, epinephrine, amrinone, and calcium chloride (CaCl2) were measured before (normal) and 30 min after a 15-min-period occlusion of the left anterior descending artery (stunned) in an open-chest canine model. Percent segment shortening (%SS) and post-systolic shortening (%PSS) were determined. Myocardial extraction of oxygen (EO2) and lactate (E(lac)) was calculated. The inotropic drugs increased %SS, CBF, and MVO2 in normal myocardium. Epinephrine and amrinone decreased, while dobutamine and CaCl2 did not affect EO2. The ischemia and reperfusion itself significantly reduced %SS and E(lac), and increased %PSS. In stunned myocardium, the responses to inotropic drugs were not significantly altered, except that they progressively reduced %PSS and epinephrine did not affect EO2. These findings indicate that a brief episode of ischemia does not affect the mechanical and metabolic coronary flow responses to inotropic drugs, although it abolishes direct vasodilator responses to epinephrine.
Amrinone/administration and dosage ; Animals ; Calcium Chloride/administration and dosage ; Cardiotonic Agents/*administration and dosage ; Comparative Study ; Dobutamine/administration and dosage ; Dogs ; Dose-Response Relationship, Drug ; Epinephrine/administration and dosage ; Female ; Male ; Myocardial Contraction/*drug effects ; Myocardial Stunning/*drug therapy/etiology/*physiopathology ; Oxidation-Reduction/drug effects ; Oxygen Consumption/*drug effects ; Reperfusion Injury/complications/*drug therapy/*physiopathology ; Treatment Outcome