A Rare Case of Transient Second-Degree Mobitz Type II Heart Block Complicating a Saddle Pulmonary Embolism

Presentations of pulmonary embolism (PE) are often associated with various cardiac arrhythmias and conduction abnormalities detected on electrocardiograms (EKG). We describe a 65-year-old female with no known history of heart disease or arrhythmias who presented with an acute onset of shortness of breath. Initial EKG showed right bundle branch block (RBBB), and first-degree atrioventricular (AV) block with subsequent development of second-degree Mobitz type II AV block. The patient’s clinical appearance was highly suggestive of a massive pulmonary embolism with hemodynamic instability, and treatment with alteplase (tPA) was given, followed by heparinization. A CT pulmonary angiography confirmed the provisional diagnosis and revealed a large saddle embolus within the right and left main pulmonary arteries. Subsequent EKG showed resolution of the RBBB, first-degree AV block, and second-degree AV block. The patient improved clinically and was discharged to a subacute rehab facility with follow-up appointments. This case highlights that pulmonary embolism may present with many EKG changes, including RBBB, first-degree, second-degree, or complete heart block. Early recognition of PE and thrombolytic treatment can improve cardiac function and restore heart rhythms. Further evaluation for underlying conduction abnormalities can later be performed.