Does location matter? Prognostic value of single-photon emission computed tomography myocardial perfusion imaging by vascular territory

The location of a myocardial perfusion abnormality frequently affects clinical decision making, especially if the left anterior descending artery (LAD) territory is involved. The purpose of this study was to determine whether the location of abnormalities on single-photon emission computed tomography (SPECT) imaging affects outcomes. We retrospectively analyzed 21,294 consecutive patients with known or suspected coronary artery disease who underwent exercise or pharmacological stress SPECT over a 10-year period. Using the ASNC 17-segment model, 2 observers interpreted images with regards to defect severity, size, and reversibility. The summed stress score (SSS) was used in relation to vascular territories [LAD, right coronary artery (RCA), and left circumflex artery (LCx)]. All patients were followed over a mean period of 2.5 +/- A 2 years for cardiac events (cardiac death or non-fatal myocardial infarction). Of the enrolled patients, 5,676 had single-vessel territory defects with a mean SSS of 4.3 +/- A 2.8. Cardiac event-free survival curves revealed no significant difference between the 3 locations (LAD, RCA, and LCx) (P = .235). When compared by mild (2-3), moderate (4-8), or severe (> 8) SSS, outcomes between the 3 groups were again similar. There were 2,907 patients with two-vessel territory defects with a mean SSS of 10.8. Outcomes were similar between the following 2 groups: two-vessel with LAD involvement and two-vessel without LAD involvement (P = .558). In patients with single- or two-vessel territory perfusion abnormalities with similar size and severity of perfusion defects, the location of defect did not impact future cardiac events. Location of myocardial perfusion defect on SPECT imaging may not be helpful in clinical decision making.