THALLIUM SCINTIGRAPHY COMPARED WITH F-18 FLUORODEOXYGLUCOSE POSITRON-EMISSION-TOMOGRAPHY FOR ASSESSING MYOCARDIAL VIABILITY IN PATIENTS WITH MODERATE VERSUS SEVERE LEFT-VENTRICULAR DYSFUNCTION

Thallium-201 reinjection imaging and positron emission tomography prov ide concordant information regarding myocardial viability in many pati ents with coronary artery disease and left ventricular (LV) dysfunctio n. It is unclear whether this concordance applies to patients with sev ere, as well as those with moderate, LV dysfunction. We studied 44 pat ients with chronic coronary artery disease and LV dysfunction, subgrou ped on the basis of severity of dysfunction: 23 patients had moderate and 21 had severe dysfunction (ejection fractions 34 +/- 6% and 19 +/- 6%). Patients underwent exercise thallium single-photon emssion compu ted tomography (SPECT) with 3- to 4-hour redistribution and reinjectio n imaging, as well as positron emission tomography (PET) imaging with (18)fluorodeoxyglucose and O-15-water. Data were analyzed quantitative ly in aligned transaxial PET and SPECT tomograms. A myocardial region was considered nonviable by PET if (18)fluorodeoxyglucose activity was <50% of that in a normal region, associated with proportional reducti on in blood flow. Similarly, regions were considered nonviable by thal lium if activity was <50% of activity in normal regions on redistribut ion and reinjection studies. Thallium SPECT and PET data were concorda nt regarding viability in 98% and 93% of myocardial regions, respectiv ely, in patients with moderate and with severe LV dysfunction. Lower c oncordance was observed only when regions with severe irreversible tha llium perfusion defects on redistribution images were considered in bo th groups: 86% and 78%, respectively (p <0.01). Thus, thallium SPECT w ith reinjection yields information regarding regional myocardial viabi lity that is similar to that provided by PET in patients with severe a s well as moderate LV dysfunction. However, there is discordance in >2 0% of regions manifesting severe irreversible thallium defects in pati ents with severely reduced LV function. (C)1998 by Excerpta Medica, In c.