Comparison of 201Tl scintigraphy and low-dose dobutamine echocardiography for the noninvasive assessment of myocardial viability.

Abstract

Noninvasive assessment of myocardial viability has proved clinically useful to distinguish hibernating or stunned myocardium from irreversibly injured myocardium in patients with chronic CAD or recent myocardial infarction who exhibit severe regional and global LV dysfunction. A variety of noninvasive methodologies are undergoing investigation and validation for determination of accuracy in the detection of preserved viability in akinetic and severely hypokinetic myocardium. These techniques include SPECT perfusion imaging with 201Tl or one of the new 99mTc-labeled agents, such as 99mTc sestamibi; SPECT imaging of 123I-labeled fatty acid analogs; PET imaging of regional flow and 18F-labeled FDG uptake; and assessment of inotropic reserve by use of dobutamine echocardiography. A major clinical objective when one of these techniques is used in CAD patients with ischemic cardiomyopathy is to identify those who will benefit most from coronary revascularization with respect to postoperative improvement in regional and global LV function, heart failure symptoms, functional capacity, and enhanced long-term survival. Several observational studies1 2 3 4 showed substantial survival benefit with revascularization compared with medical therapy in patients whose low ejection fraction was primarily due to viable but hibernating myocardium. Similarly, preliminary data5 suggest that patients with low ejection fractions, multivessel CAD, and preserved viability who undergo CABG have a lower perioperative mortality and morbidity and a greater long-term survival rate than patients with a comparable degree of LV dysfunction and angiographic extent of CAD who undergo surgery but who manifest poor myocardial viability preoperatively. Gioia et al1 reported a 13% annual mortality rate in CAD patients with LV dysfunction and presence of viability by 201Tl criteria who were treated medically compared with 6% for those with comparable viability who underwent revascularization. DiCarli et al2 reporteda 50% mortality rate at 1 year in patients with …