1010-122 Stress-Rest Dobutamine SPECT Tc-99m Sestamibi Accurately Predicts Myocardial Viability in Dysynergic Left Ventricular Segments

There has been increasing controversy regarding the ability of SPECT Tc99m Sestamibi (MIBI) for identification of myocardial viability in regions of the left ventricle affected by severe wall motion abnormality. We have evaluated 27 patients with documented coronary artery disease (CAD) and severe regional wall motion abnormality of the left ventricle due to CAD. All patients underwent low dose (5–10μg/kg) dobutamine echocardiography and maximal (15–40μglkg/min) stress dobutamine MIBI. A separate day SPECT MIBI was performed at rest. The left ventricle was divided into 3 regions; a total of 37 regions were found to have severe wall motion abnormality by echocardiography, of which 35 showed improved wall thickening with low dose dobutamine (gold standard for myocardial viability in this study). Rest MIBI uptake was assessed semiquantitatively for each of the matching regions, and this was graded from 1 to 4, from normal to absent perfusion. Regions with myocardial perfusion of a grade of 3 or less were considered viable by rest MIBI. Rest MIBI detected viability in 32 (93%) of the viable regions, as defined by echocardiography, the concordance was 92% (kappa=0.54, P<0.001). Furthermore, stress-rest MIBI revealed completely reversible defects in 18 (23%), partially reversible defects in 24 (69%) and Grade 4 uptake and fixed (non-viable) defects in 3 (8%) regions defined as viable by dobutamine echocardiography. Thus, rest MIBI is a good indicator of myocardial viability in left ventricular segments showing severe regional dysynergy, and reversible ischaemia detected by stress-rest dobutamine MIBI in these segments provides further proof that sestamibi SPECT accurately defines regional myocardial viability