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.