ECG Diagnosis: Pulmonary Embolism
Fall 2011 - Volume 15 Number 4
The S1Q3T3 sign (prominent S wave in lead I, Q wave and inverted T wave in lead III) is a sign of acute cor pulmonale (acute pressure and volume overload of the right ventricle because of pulmonary hypertension) and reflects right ventricular strain.1 This electrocardiogram (ECG) finding is present in 15% to 25% of patients ultimately diagnosed with pulmonary emboli (PE).2 Any cause of acute cor pulmonale can result in the S1Q3T3 findings on ECG, including PE, acute bronchospasms, pneumothorax, and other acute lung disorders. Other ECG findings noted during the acute phase of a PE include new right bundle branch block (complete or incomplete), rightward shift of the QRS axis, ST-segment elevation in V1 and aVR, generalized low amplitude QRS complexes, atrial premature contractions, sinus tachycardia, atrial fibrillation/flutter, and T wave inversions in leads V1-V4.2 The ECG is often abnormal in PE, but findings are neither sensitive nor specific for the diagnosis of PE.3 The greatest utility of the ECG in a patient with suspected PE is ruling out other life-threatening diagnoses (eg, acute myocardial infarction).
1. Chan TC, Vilke GM, Pollack M, Brady WJ. Electrocardiographic manifestations: pulmonary embolism. J Emerg Med 2001 Oct;21(3):263-70.