A Broken Heart: Cardiac Arrest As the Initial Presentation of Myasthenic Crisis

Myasthenic crisis is a life-threatening condition commonly associated with respiratory failure and may present in unusual ways. However, there is paucity in the literature about the cardiac manifestations of myasthenia gravis. We present a case of a 61-year-old male who presented to the emergency room with upper respiratory infection symptoms who soon thereafter suffered sudden cardiac arrest. He was found to have shortened PR interval pre and post arrest onelectrocardiogram (EKG). Only past medical history, discovered post cardiac arrest, was myastenia gravis. All other causes of cardiac arrest were ruled out, and it was deemed to be due to a manifestation of myastenia gravis. The patient was treated with intravenous steroids and plasmapheresis with resolution of shortened PR interval. It is hypothesized that striatial muscle antibodies may trigger inflammation in cardiac muscle and cause conduction abnormalities. In addition, anti-Kv1.4 antibodies have been associated with EKG abnormalities, including QT prolongation and T-wave inversion. To our knowledge, we are the first to report myasthenic crisis manifesting with isolated cardiac arrest with pulseless electrical activity and a shortened PR interval.