prognostic significance of ischemic electrocardiographic changes with regadenoson stress myocardial perfusion imaging

In patients undergoing regadenoson spect myocardial perfusion imaging (mpi), the prognostic value of ischemic st-segment depression (st↓) and the optimal st↓ threshold have not been studied. a retrospective cohort study of consecutive patients referred for regadenoson stress mpi was conducted. patients with uninterpretable ecg were excluded. two diagnostic thresholds of horizontal or downsloping st↓ were studied, ≥ 0.5 mm and ≥ 1.0 mm. the primary endpoint was the composite major adverse cardiac events (mace) of cardiac death, myocardial infarction, or coronary revascularization. among 8615 subjects (mean age 62 ± 13 years; 55% women), 89 (1.0%) had st↓ ≥ 1.0 mm and 133 (1.5%) had st↓ ≥ 0.5 mm. regadenoson-induced st↓ was more common in women (p < .001). mean follow-up was 2.5 ± 2.2 years. after multivariate adjustment, st↓ ≥ 1.0 mm was associated with a non-significant increase in mace risk (p = .069), irrespective to whether mpi was abnormal (p = .162) or normal (p = .214). ischemic st↓ ≥ 0.5 mm was independently associated with mace in the entire cohort (hr 2.14; ci 1.38-3.32; p = .001), whether mpi is normal (hr 2.07; ci 1.07-4.04; p = .032) or abnormal (hr 2.24; ci 1.23-4.00; p = .007), after adjusting for clinical and imaging covariates. an st↓ threshold of ≥ 0.5 mm provided greater incremental prognostic value beyond clinical and imaging parameters (δχ2 = 12.78; p < .001) than ≥ 1.0 mm threshold (δχ2 = 3.72; p = .093). regadenoson-induced ischemic st↓ is more common in women and it provides a modest independent prognostic value beyond mpi and clinical parameters. st↓ ≥ 0.5 mm is a better threshold than ≥ 1.0 mm to define ecg evidence for regadenoson-induced myocardial ischemia.