Serial changes on quantitative myocardial perfusion SPECT in patients undergoing revascularization or conservative therapy

Background. Little is known about changes of myocardial perfusion in patients undergoing coronary revascularization or medical therapy. The purpose of this observational study was to assess the long-term effects of revascularization or conservative therapy on serial quantitative myocardial perfusion single photon emission computed tomography (SPECT). Methods and Results. The study population consisted of 421 patients who underwent serial rest thallium-201/stress technetium-99m sestamibi dual-isotope myocardial perfusion SPECT with at least a 1-year interval between the 2 studies and who had abnormal quantitative scan results on the first stress SPECT. The mean interval between scans was 32.7 +/- 15.9 months. Patients were divided into 3 groups according to stress defect extent: group I had small stress defects (4%-10%, n = 145), group 2 had intermediate stress defects (>10%-20%, n = 144), and group 3 had extensive stress defects (>20%, n = 132) at baseline. Forty patients in group 1, 44 in group 2, and 54 in group 3 underwent coronary revascularization between 2 SPECT studies; the others had conservative therapy. In group 3 patients with revascularization, stress defect extent and reversible defect extent were remarkably reduced (14.5% +/- 13.6% and 13.1% +/- 12.5%, respectively; both P < .0001), with greater improvement in those patients reporting increased use of cardiac medications; resting defect extent was slightly reduced (1.9% <plus/minus> 6.4%, P < .05). In group 3 patients with conservative therapy, a small reduction in stress defect extent was noted (2.3% <plus/minus> 8.3%, P < .05). In group 2, there were modest, similar reductions in reversible defect extent in both the patients with revascularization (2.7% <plus/minus> 7.7%, P < .05) and those with conservative therapy (1.8% <plus/minus> 7.3%, P < .05), as well as a small but significant reduction in stress defect extent in those with conservative therapy (2.1% <plus/minus> 8.2 %, P < .05). In group 1 patients, no significant changes in stress, rest, or reversible defect extent were found with either therapy. Conclusions. The findings of this study show that improvement in quantitative myocardial perfusion abnormalities over time occurs in some patients with either revascularization or conservative therapy and suggest that, in patients with extensive defects, greater improvement may be seen in those who undergo revascularization.