Underestimating the Risk of an Inconclusive Result in Exercise Treadmill Tests for Patients With Suspected Ischemic Heart Disease

Abstract

Background: The exercise stress test is a widely used noninvasive test for diagnosing ischemic heart disease. Patients with a “positive” result have a higher risk than those with a “negative” result. However, the outcomes of patients with an “inconclusive” result remain uncertain. Methods and Results: We retrospectively collected the data of patients who underwent an ECG-based treadmill stress test between August 2009 and March 2020. Propensity score matching (PSM) was performed to adjust for confounders. Clinical outcomes were compared in terms of all-cause death and cardiovascular (CV) death. Subgroup analysis evaluated treatment interactions, including medication and examinations. In total, 25,475 patients were recruited, and after exclusion and PSM, 4,847 (1,621 with a positive result, 1,606 with a negative result, and 1,621 with an inconclusive result) remained. Compared with the negative group, the inconclusive group, but not the positive group, had a significantly worse outcome in terms of all-cause death (hazard ratio [HR]: 1.834, 95% confidence interval [CI]: 1.34–2.511 and HR: 1.327, 95% CI: 0.949–1.857, respectively); however, CV death was not significantly different in the inconclusive and positive groups (HR: 1.728, 95% CI: 0.413–7.232 and HR: 2.067, 95% CI: 0.517–8.264, respectively). Conclusions: Clinicians must not underestimate the potential for worse outcomes in patients with an inconclusive stress test result.