Evaluation of ST-segment and T-wave changes associated with NSTE-ACS in patients with RBBB: a nested case–control study design

Patients presenting with suspected acute coronary syndrome (ACS) in the emergency department (ED) require rapid and accurate electrocardiographic (ECG) evaluation. This study aims to assess conventional ECG markers for diagnosing non-ST-elevation ACS (NSTE-ACS) in patients with chest discomfort and right bundle branch block (RBBB). A nested case–control design was employed to compare patients with RBBB admitted to the ED for suspected cardiac ischemia, focusing on those who developed NSTE-ACS versus those who did not. The sample consisted of 352 patients with suspected ACS and RBBB identified on ECG. Among them, 88 were diagnosed with NSTE-ACS. In the presence of RBBB, ST-segment elevation on the isoelectric line and/or positive T-waves on the ECG were significantly associated with the diagnosis of NSTE-ACS (p < 0.05). In patients who developed NSTE-ACS, the likelihood of an isoelectric ST-segment was 3.48 (95% CI 2.07–5.82) times higher, the likelihood of positive T-waves was 4.16 (95% CI 2.51–6.91) times higher, and the combination of an isoelectric ST-segment with positive T-waves was 4.81 (95% CI 2.28–8.25) times higher (p < 0.05). In addition, ST-segment depression and non-negative T-waves were significantly more frequent in patients who developed NSTE-ACS, with odds ratios of 5.78 (95% CI 3–11.3), compared to those who did not (p < 0.05). The odds ratios for ST-segment and T-wave changes were 2.81 and 3.47, respectively, with an 80% correct classification rate for predicting NSTE-ACS. Clinicians should closely monitor the presence of an isoelectric ST-segment and positive T-waves in patients with RBBB to assess for potential cardiac ischemia.