Reproducibility of myocardial thallium-201 washout in studies applying a standardized dipyridamole stress protocol

Thallium-201 (201Tl) washout analysis was proposed as an adjunctive tool to improve the detection of coronary artery disease (CAD). Since reproducibility of 201Tl washout in dipyridamole (DPM) stress studies is unknown, this item was evaluated in 32 patients (24 with CAD, 8 without CAD), who were scintigraphed twice within 1-2 weeks. At 2 minutes following DPM infusion (0.5 mg/kg/5 min), 2 mCi 201Tl were injected. Global and segmental washout were calculated by comparing circumferential profiles of respective background-corrected stress (left anterior oblique (LAO) 45 degrees: 8 min postinfusion (p.i.), 35 min p.i.; anterior (ANT): 17 min p.i.; LAO 70 degrees: 26 min p.i.) and redistribution (4 h p.i.) images. Whereas visual findings were comparable for study I and II, reproducibility of 201Tl washout was low, indicated by comparing variances among patients with variance between studies, which were 28.8 and 71.2% of total variance, respectively. Mean differences of segmental washout between the studies ranged from 9.75 to 19.24% with only minor differences with regard to the different views and segments evaluated. Variability was lower using the intermediate instead of the initial scintigram as reference for the redistribution image (12.87 +/- 11.64% vs. 18.59 +/- 14.43%, n = 85; p less than 0.01). Variability was higher for nonstenosed compared to stenosed segments (14.54 +/- 11.41%, n = 32 vs. 9.89 +/- 8.03%, n = 28, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)