Transient Right Bundle Branch Block with S1Q3T3 Pattern in Pulmonary Embolism

A 69-year-old woman with hypertension, hyperlipidemia, sleep apnea, gastroesophageal reflux disease, and recent knee replacement was brought to the emergency room (ER) for syncope. She had her physiotherapy session earlier in the day and became symptomatic with dizziness, shortness of breath and had loss of consciousness. In the ER, systolic blood pressure (SBP) was noted to be 90 mmHg and an oxygen saturation (O2 sat) of 80% on room air. Patient received fluid bolus with improvement of SBP to 110 mmHg. O2 sat improved to 99% with 10 L of oxygen. A bedside echocardiogram showed right ventricular (RV) distension. A Computerized Tomographic Angiogram (CTA) of the chest showed bilateral main stem pulmonary emboli (PE) with signs of RV strain. Initially EKG showed sinus tachycardia, right bundle branch block, and a S1Q3T3 pattern which resolved rapidly the next day. Patient was admitted, remained hemodynamically stable, and was treated with full dose of Enoxaparin subcutaneously. A follow up EKG was performed the next day, which showed complete resolution of initial findings. Follow up echocardiogram also showed rapid resolution of RV strain and complete restoration of RV size and function. Patient was eventually discharged home on full dose apixaban.