Prevalence of electrocardiographic abnormalities in patients with myasthenia gravis

Myasthenia gravis (MG) is an immunological disorder of the neuromuscular junction, characterized by easy fatigability and weakness of the skeletal muscles. However, it has sometimes been reported that heart diseases including cardiomyopathies leading to sudden death have been observed in patients with MG. We studied the prevalence of electrocardiographic (ECG) abnormalities and heart disease in patients newly diagnosed with MG who had not received immunotherapy.

Fifty-three patients with MG were enrolled in our study. We reviewed the ECG recordings of all patients on admission, and assessed the prevalence of ECG abnormalities and heart diseases associated with MG.

Thirty-three (62.2%) patients had ECG abnormalities, including early repolarization (15 patients), negative T waves (9 patients), left ventricular hypertrophy (5 patients), and prolonged QTc (4 patients). A higher frequency of early repolarization was observed in patients with MG compared to healthy subjects.

ECG abnormalities in patients with MG were more prevalent in our series than in the general population. This may be because of the increasing incidence of MG in the elderly. However, we also observed that younger patients developed severe heart disease, indicating the possibility of other mechanisms, such as the presence of antimyocardial antibodies. Clinicians should be aware of the complications of heart disease in patients with MG, especially during the perioperative period for thymectomy or thymomectomy.