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.

BACKGROUND: The critical threshold and clinical significance of transient ischemic dilation (TID) for regadenoson, single-isotope (99m)Tc SPECT myocardial perfusion imaging (MPI) are not defined.

METHODS: 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, (99m)Tc-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.

RESULTS: 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).

CONCLUSIONS: The clinical utility of TID with regadenoson-stress MPI in this era of declining CAD burden is questionable.