Classical ECG findings in pulmonary embolism have minimal diagnostic accuracy: A cross-sectional study.

Pulmonary embolism (PE) can present with several "classic" electrocardiographic (ECG) abnormalities-most notably the S1Q3T3 pattern, right ventricular (RV) strain, right bundle branch block, sinus tachycardia, and T-wave inversions. We prospectively studied every adult who underwent computed tomography pulmonary angiography (CTPA) for suspected PE in a tertiary cardiology hospital between January 2021 and December 2023. All 12-lead ECGs acquired on the same day or after CTPA were interpreted by blinded cardiologists. Diagnostic accuracy (sensitivity, specificity, positive and negative likelihood ratios [LR+, LR-]) and multivariable logistic regression were calculated for each predefined ECG criterion; clinical utility was judged by whether the 95 % confidence interval (CI) of LR+ or LR- crossed 1. Of 273 consecutive patients (mean age 61 years; 54 % women), PE was confirmed in 75 (27.5 %), including 14 subsegmental events. In the multivariable model, only sinus tachycardia (OR 1.93, 95 % CI 1.09-3.41) and inversion/flattening of inferior T-waves (OR 1.82, 95 % CI 1.04-3.18) remained significant. Among traditional signs, S1Q3T3 yielded LR+ 2.07 (95 % CI 1.27-3.39) and liberal RV strain (inverted/flattened T-waves in ≥2 inferior +≥2 anterior leads) yielded LR+ 4.75 (95 % CI 2.3-9.8); all other findings were noninformative. Reclassifying subsegmental emboli as controls did not materially change results. Overall, classical ECG findings modestly increase post-test probability but lack sufficient standalone accuracy, underscoring that ECG should not be used in isolation to rule in or rule out PE.