The impact of right bundle branch block and SIQIII-type patterns in determining risk levels in acute pulmonary embolism

Background: Electrocardiography (ECG) findings in acute pulmonary embolism (PE) are known to be related to various right ventricular (RV) alterations. These abnormalities are not included in risk stratification algorithms despite emerging evidence of their association with patient outcomes. We aimed to analyze the impact of right bundle branch block (RBBB) and/or SIQIII patterns as indicators for determining the level of risk in patients with PE. Methods: We performed a retrospective cohort study including all patients with confirmed acute PE hospitalized from January 2008 to December 2019 in two tertiary care cardiology departments. The first ECG taken at admission was selected and the analysis focused on the presence of a complete or an incomplete RBBB and SIQIII-type patterns. Results: A total of 255 patients were divided into two groups: Group I (47.8%, n=122) included patients with PE without RBBB nor SIQIII patterns, and Group II (52.2%, n=133) included patients with RBBB and/or SIQIII patterns. Patients in group II presented significantly more frequently with acute right heart symptoms (45.1% vs. 18%, p<0.001) and cardiogenic shock at admission (31.6 vs. 4.1%, p<0.001). Echocardiographic parameters indicating right heart injury also occurred more significantly in group II patients (p<0.001). By univariate analysis, patients in group II were found to be significantly associated with in-hospital mortality (22.6 vs. 6.1%, p=0.002) and major cardiovascular events (MACEs) during hospitalization (43.3 vs. 13.7%, p<0.001). Multivariate logistic regression analysis identified five independent factors predictive of MACEs: SIQIII and/or RBBB, renal failure, positive troponin levels, RV dysfunction and right heart failure symptoms during initial presentation. Kaplan-Meier survival analysis identified the inclusion in Group II and the presence of SIQIII pattern as predictors of overall mortality (p<0.001). Conclusions: Our study suggests an important and independent prognostic value of RBBB and SIQIII patterns and their usefulness in determining the outcome of PE patients.