MYOCARDIAL TL-201 SCINTIGRAPHY FOR ASSESSMENT OF VIABILITY IN PATIENTS WITH SEVERE LEFT-VENTRICULAR DYSFUNCTION

Many patients with ischemic heart disease and depressed left ventricular (LV) function have asynergic zones with sustained microcirculatory perfusion and myocardial metabolic activity that exhibit improved systolic function after coronary revascularization. The 2 predominant noninvasive techniques used to determine myocardial viability in patient with severely depressed LV function are thallium-201 (Tl-201) scintigraphy and positron emission tomography (PET). Myocardial extraction of Tl-201 is unaltered under experimental conditions of myocardial stunning or short-term hibernation (characterized by flow and ischemic dysfunction). Akinetic or dyskinetic LV wall segments can exhibit normal or near normal Tl-201 uptake as long as some residual flow is present. Tl-201 scintigraphy can identify viable asynergic segments when performed on patients with severe coronary artery disease who are in the resting state. Many of these patients have initial resting defects that demonstrate delayed redistribution, or mild persistent defects that show improved perfusion and function after revascularization. There is a direct correlation between the extent of Tl-201 uptake in zones af severe regional myocardial asynergy and the magnitude of improvement in resting LV ejection fraction after coronary bypass surgery. Rest Tl-201 scintigraphy may help in the selection of patients with coronary artery disease and severely depressed LV function who would benefit the most from revascularization.