Characteristic ECG finding of pulmonary embolism
**Core Concept**
Pulmonary embolism (PE) is a condition where a blood clot blocks an artery in the lungs, leading to acute right heart strain. The characteristic ECG finding of PE is a result of this strain on the right ventricle.
**Why the Correct Answer is Right**
The correct ECG finding of PE is a **right bundle branch block (RBBB)**. This is due to the acute right ventricular strain caused by the pulmonary embolism, leading to delayed activation of the right ventricle. The RBBB pattern is characterized by a wide QRS complex (> 120 ms) with a notched or slurred R wave in lead V1. This is often accompanied by other signs of right ventricular strain, such as T-wave inversion in leads V1-V3.
**Why Each Wrong Option is Incorrect**
* **Option A:** While ST-segment elevation in leads V1-V3 can be seen in PE, it is not the characteristic ECG finding.
* **Option B:** P-wave abnormalities, such as P-pulmonale, can be seen in conditions affecting the left atrium or pulmonary hypertension, but are not specific for PE.
* **Option C:** T-wave inversion in leads V1-V3 can be seen in various conditions, including coronary artery disease, but is not the characteristic ECG finding of PE.
* **Option D:** Atrial fibrillation can be seen in PE, but is not the characteristic ECG finding.
**Clinical Pearl / High-Yield Fact**
Remember the "S1Q3T3" pattern, which is classically associated with pulmonary embolism. This pattern consists of a loud S1 heart sound, Q wave in lead I, and T-wave inversion in lead III.
**Correct Answer: C. Right bundle branch block.**