Cardiac involvement in myasthenia gravis--is there a specific pattern?

Myasthenia gravis is an autoimmune neuromuscular disorder characterized by skeletal muscle involvement, causing muscle weakness and fatigue. The prevalence of the disease is approximately 1:7500 with a maximal prevalence during the second and third decade in women and the fifth and sixth decade in men, although it may appear at any age. The disease has a slight female preponderance, with a sex ratio of 3:2. Cardiac involvement in myasthenia gravis may take several forms, ranging from asymptomatic ECG changes to ventricular tachycardia, myocarditis, conduction disorders, heart failure and sudden death. We hereby report two cases of patients with myasthenia gravis who developed signs and symptoms of cardiovascular involvement, requiring admission in a cardiology ward for further investigation and treatment. The particular characteristics of the first case may be summarized by the symptomatic conduction disturbances with frequent episodes of syncope in a patient with myasthenia gravis who necessitated permanent pacing and the difficulties we encountered in the establishment of conduction disturbancies etiology (due to the disease or due to the treatment with acetylcolinesterase inhibitors). The second case shows a different kind of cardiac involvement in myasthenia gravis--the ECG changes (giant diffuse T waves in a patient with cardiovascular risk factors) which needed further investigation and long term surveillance.