The significance of automatically measured transient ischemic dilation in identifying severe and extensive coronary artery disease in regadenoson, single-isotope technetium-99m myocardial perfusion SPECT

The critical threshold and clinical significance of transient ischemic dilation (TID) for regadenoson, single-isotope Tc-99m SPECT myocardial perfusion imaging (MPI) are not defined. From 100 patients with low likelihood of CAD, we derived the abnormal TID threshold (mean + 2 SD). We validated the threshold in a cohort of 547 patients who received one-day, rest/regadenoson-stress, Tc-99m-tetrofosmin SPECT-MPI followed by coronary angiography within 6 months. Patients were classified into three CAD severity strata: no significant CAD, mild to moderate CAD, and severe and extensive CAD. The abnormal TID threshold was determined to be 1.31. Though mean TID ratios were different between the three CAD severity groups and the derivation cohort (P < .001), there was no difference in the mean TID ratios between the categories of CAD severity or in the prevalence of severe CAD between TID+ and TID- groups (P = .74). By ROC analysis, TID had a poor discriminatory capacity in identifying severe and extensive CAD [AUC of 0.55 (95% CI 0.47-0.62, P = .25)]. Stepwise multivariate logistic analysis demonstrated that adding TID to clinical and perfusion data did not provide incremental diagnostic value (P = .87). The clinical utility of TID with regadenoson-stress MPI in this era of declining CAD burden is questionable.