The diagnostic and prognostic value of regadenoson-induced ST-segment depression (ST↓) is not defined. Due to the low incidence of ST↓ ≥1.0 mm with vasodilator stress, a lower threshold to define ischemic ECG response may provide improved clinical utility.

We conducted a retrospective cohort study of patients who underwent regadenoson-stress SPECT myocardial perfusion imaging (MPI) followed by coronary angiography within 6 months. Ischemic ST↓ was defined as ≥0.5 mm. The prevalence of angiographically severe coronary artery disease (CAD) and the rates of major adverse cardiac events (MACE) including cardiac death, myocardial infarction, and coronary revascularization were determined.

In a diagnostic cohort of 629 subjects, 117 (18.6%) had ST↓ ≥0.5 mm. Severe CAD was more prevalent in the ST↓ ≥0.5 vs ST <0.5 group (13.7% vs 5.3%, P = .001). Among patients with normal MPI (n = 229), the prevalence of severe CAD was higher in the ST↓ ≥0.5 group (8.2% vs 2.2%, P = .04). Adjusting for clinical and imaging covariates, ST↓ ≥0.5 mm was independently predictive of severe CAD [odds ratio = 3.37, 95% confidence interval (CI) = 1.67-6.83, P = .001], and provided incremental diagnostic value (Chi square increment = 10.3, P = .001). In an outcome cohort of 748 subjects, after adjusting for clinical and imaging covariates, ST↓ ≥0.5 mm was associated with increased MACE rate in the entire cohort [hazard ratio = 1.41, CI 1.01-1.96, P = .04] and in the subgroup of patients with normal MPI [hazard ratio = 2.2, CI 1.11-4.39, P = .02], and provided incremental prognostic value (Chi square increment = 3.9, P = .049). A diagnostic ST↓ threshold of 0.5 mm provided greater discriminatory capacity than a 1.0 mm cutoff (P = .03).

Among patients selected to undergo coronary angiography, regadenoson-induced ST↓ ≥0.5 mm was associated with higher rates of severe CAD and MACE, irrespective of MPI finding.