Variability of myocardial perfusion defects assessed by thallium-201 scintigraphy in patients with coronary artery disease not amenable to angioplasty or bypass surgery

OBJECTIVES We sought to assess the variability of results obtained with tha llium scintigraphy as a method for tracking the extent of myocardial ischem ia in medically refractory patients with angina who are not suitable for co ronary artery bypass graft surgery or percutaneous transluminal coronary an gioplasty. BACKGROUND New therapies are being evaluated for patients with "no option" angina in whom medical therapy has failed. Nuclear techniques, like thalliu m scintigraphy, are used in multicenter trials to evaluate whether such the rapies improve myocardial perfusion. However, the variability of test resul ts is unknown in this patient group in a multicenter study. METHODS The Angina Treatments: Lasers And Normal Therapies In Comparison (A TLANTIC) study was a randomized trial of transmyocardial laser revasculariz ation (n = 182). Patients underwent dipyridamole thallium stress tests at b aseline and 3, 6 and 12 months after enrollment. The control group (n = 90) was treated with constant medical therapy during the study and is a releva nt group to investigate test variability. Test variability over time was qu antified by the mean absolute change in the percentage of reversible perfus ion defects between baseline and follow-up. RESULTS Baseline percent myocardium with ischemia averaged 17.0 +/- 13.7% a nd did not change during follow-up. However, variations in the percent myoc ardium with reversible perfusion defects over time amounted to an average o f 6 to 8 percentage points, or 43% to 55% of the baseline value. Only simil ar to 13% of this variability was attributable to variability in image reco nstruction and analysis. CONCLUSIONS As demonstrated in the ATLANTIC study, percent myocardial ische mia in control subjects receiving constant medical therapy varied in indivi dual patients by an average of similar to 50%. This may limit the utility o f thallium scintigraphy to detect improved myocardial perfusion over time i n response to therapy. (C) 2001 by the American College of Cardiology.