Atrioventricular block and myastenia gravis. A case report and review of the literature.

Objectives: Myasthenia gravis (MG) is a chronic autoimmune disease primarily affecting skeletal muscles, though cardiac involvement, particularly arrhythmias, may occur, especially in severe cases or in patients with thymoma.

Case presentation: We report the case of a 62-year-old male with AchR-Ab-positive MG, without thymoma, who developed an advanced atrioventricular block requiring pacemaker implantation. Cardiac manifestations in MG can result from either the disease itself - through myocarditis, autoantibodies and autonomic dysfunction - or as a side effect of treatments such as pyridostigmine and immunosuppressants. Management strategies include considering discontinuation of pyridostigmine or using hyoscyamine to assess potential drug-induced bradyarrhythmias before proceeding with permanent pacing.

Conclusions: This case highlights the diagnostic challenges in distinguishing iatrogenic from autoimmune cardiac complications and emphasizes the importance of cardiovascular monitoring in MG patients, especially those presenting with cardiac symptoms or EKG abnormalities. Early recognition and appropriate intervention are crucial to improve outcomes and quality of life.