Washout Reflects Impaired Myocardial Contractile and Relaxation Reserve During Dobutamine Stress Due to Mitochondrial Dysfunction in Dilated Cardiomyopathy Patients

Methods Twenty DCM patients (New York Heart Association functional class I–III) underwent myocardial Tc-MIBI scintigraphy and cardiac catheterization. Myocardial MIBI uptake was quantified as an early and delayed heart-tomediastinum ratio, and WR was calculated. Maximum first derivative of left ventricular (LV) pressure (LV dP/dtmax) (an index of myocardial contractility) and LV pressure half-time (T1/2) (an index of myocardial relaxation) were calculated by the left ventricular pressure curve at baseline and during dobutamine infusion (15 g/kg/min at maximum). Endomyocardial biopsy specimens were obtained for quantitative mRNA analysis and electron microscopy. The patients were divided into two groups as follows: 1) group A of 10 patients showing a WR 24.3% (median value) and 2) group B of 10 patients showing a WR 24.3%.