(167) Blocked Twice: Pulmonary Embolism as Etiology of Complete Heart Block

Introduction: Pulmonary Embolism (PE) can present with a variety of cardiac arrhythmias and conduction abnormalities. We describe a case of third degree heart block secondary to massive PE.

Description: A 71 year old male with hypertension and alcohol use disorder presented to the Emergency Department with subacute malaise and dyspnea. Electrocardiogram (ECG) showed third degree heart block with junctional escape and right axis deviation. Prior ECGs were normal sinus rhythm. He was admitted to the Intensive Care Unit with shock. His heart rate on admission was 64 and initial ScVO2 of 53% correlated with a FICK Cardiac Index (CI) of 1.2 with a calculated stroke volume of 41.8ml. An echo showed a severely enlarged, hypokinetic right ventricle with right ventricular systolic pressure of 71.6mmHg. CT pulmonary angiography demonstrated a large saddle PE with occlusion of left lower lobe, lingular, and right sided pulmonary arteries. He was treated with a heparin infusion, intravenous (IV) tenectaplase 50mg and taken for suction thrombectomy with Interventional Radiology. He then developed refractory pulsatile ventricular tachycardia despite over 600mg IV amiodarone and 400mg IV lidocaine boluses, overdrive ventricular pacing, stellate ganglion blockade and 9 synchronized cardioversions. He required AV pacing with eventual resolution of his ventricular arrhythmia and was discharged home with no sequalae.

Discussion: PE causes cardiac arrhythmias and conduction abnormalities including sinus tachycardia, S1Q3 QRS in lead I, T-wave inversion in lead III, and right bundle branch block (RBBB). The right bundle is anatomically superficial and overdistention leads to subendocardial ischemia in cor pulmonale. The exact mechanism of PE leading to complete heart block is unknown. Two possible explanations exist in the literature. First, obstructive blood flow leads to poor coronary perfusion and atrioventricular nodal ischemia. Second the Bezold-Jarisch reflex (apnea, bradycardia and hypotension) occurs following a hyperadrenergic state. This case represents a rare cause of complete heart block caused by massive PE that resolved with management of his cor pulmonale.