Significance of indeterminate and abnormal stress electrocardiography despite normal imaging in patients with suspected coronary artery disease - An analysis of the PROMISE trial.

BACKGROUND: Abnormal and indeterminate electrocardiographic (ECG) changes during cardiac stress imaging are not uncommon. While the prognostic importance of abnormal ECG despite normal imaging has been previously studied, prognosis of indeterminate stress ECG changes is uncertain. METHODS: We studied the prognostic value of stress ECG changes in symptomatic patients without known CAD and normal stress imaging from the PROMISE trial. Patients with normal ECG (concordant), indeterminate ECG and abnormal ECG (discordant) were identified among those with negative exercise imaging stress test (EIST) and negative vasodilator nuclear stress test (PIST). Outcomes of interest were major adverse cardiovascular endpoint (MACE, including all-cause mortality, myocardial infarction, and unstable angina hospitalization) and likelihood of coronary revascularization. RESULTS: In EIST, indeterminate stress ECG [1.1% vs. 0.2% adjusted hazard ratio (aHR) 4.2, (95% CI 1.11-15.6), p = 0.034] and discordant ECG [7.2% vs. 0.2% adjusted hazard ratio (aHR) 27.6, (95% CI 9.6-79.8), p < 0.0001] were associated with increased likelihood of revascularization compared to normal stress ECG. Similar findings were observed with PIST [indeterminate vs concordant [1.7% vs. 0.5% adjusted hazard ratio (aHR) 5.9, (95% CI 1.1-31.7), p = 0.041; discordant vs concordant 15.4% vs. 0.5% adjusted hazard ratio (aHR) 24.2, (95% CI 4.6-127.7), p = 0.0002]. MACE rates were similar between ECG subgroups, in both EIST and PIST. CONCLUSION: In symptomatic patients without known CAD undergoing stress imaging, indeterminate and discordant ECG changes results may indicate presence of obstructive CAD despite normal imaging results and predict increased likelihood of coronary revascularization despite no significant difference in MACE.