Pulmonary embolism (PE) is one of the leading causes of cardiovascular mortality worldwide. Electrocardiography (ECG) may provide useful information for patients with acute PE. In this study, we aimed to investigate the diagnostic value of the QRS duration and RS time in inferolateral leads in patients admitted to the emergency department, and pre-diagnosed with acute PE.

We retrospectively enrolled 136 consecutive patients, admitted to the emergency department, pre-diagnosed with the clinical suspicion of acute PE, and underwent computerized tomographic pulmonary angiography (CTPA) to confirm the PE diagnosis. The study subjects were divided into two groups according to the presence or absence of PE, and the independent predictors of PE were investigated.

Sixty-eight patients (50%) had PE. Patients with PE had a longer RS time. Among the ECG parameters, only RS time was an independent predictor of PE (OR: 1.397, 95% CI: 1.171–1.667; p < 0.001). The ROC curve analyses revealed that the cut-off value of RS time for predicting acute PE was 64.20 ms with a sensitivity of 85.3% and a specificity of 79.4% (AUC: 0.846, 95%CI: 0.749–0.944; p < 0.001). In the correlation analyses; the RS time was correlated with RV end-diastolic diameter (r = 0.422; p < 0.001), RV/left ventricle (LV) ratio (r = 0.622; p < 0.001), and systolic pulmonary artery pressure (SPAP) (r = 0.508; p < 0.001).

As a novel ECG parameter, RS time could be measured for each patient. A longer RS time can be a very useful index for diagnosing acute PE as well as for estimating the RV end-diastolic diameter and SPAP.