The role of sestamibi scintigraphy in the radioisotopic assessment of myocardial viability

The relationship between sestamibi uptake as a marker of myocardial viability and postrevascularization function recovery is still to be defined. We studied 14 patients (13 males, 1 female, mean age 55 ± 7 yr, range 35 to 64 yr) with sestamibi scintigraphy, quantitative coronary angiography and two-dimensional echocardiography. Sestamibi uptake was quantified from planar images and expressed as percent of maximal activity in each projection using a 13-segment model. All defects were subgrouped on the basis of the severity of reduction in sestamibi uptake; the limit of viability was set at 2.5 s.d. below the normal uptake (55%). Echocardiography was analyzed using a score index ranging from 1 (normokinesis) to 4 (dyskinesis) and a corresponding regional model. Before revascularization, 42 segments were grouped as normal (coronary stenosis 50% coronary stenosis, 67 had normal wall motion (Group 2) and 73 showed regional dyssynergies (Group 3). Sestamibi percent activity was high in Group 1 and significantly reduced in both Group 2 and 3 segments. Pre- and postrevascularization echocardiography was compared in all patients. Sestamibi sensitivity and specificity in the detection of postrevascularization recovery of function was 83% and 71%, respectively; positive predictive accuracy was 79%. The presence of a severe defect identified most of those segments with wall motion abnormalities that did not recover following coronary revascularization; however, sestamibi overestimated rest perfusion defects in 25% of territories supplied by stenotic coronary arteries that had normal wall motion at rest. Sestamibi appears to be primarily a perfusion agent that can provide limited information regarding viability.