Left ventricular long-axis function in myasthenia gravis.

Myasthenia gravis (MG) primarily affects skeletal muscles, but influence on cardiac function has been suggested. The aim of this study was to assess left ventricular long-axis function in MG patients compared to healthy controls, and to examine whether any MG-related heart involvement was influenced by the acetylcholine-esterase inhibitor pyridostigmine. We found that early diastolic atrioventricular-plane velocity and tissue Doppler peak systolic strain was lower in MG patients than in controls before pyridostigmine. The differences disappeared following administration of pyridostigmine. Also, tissue velocities at systole and early diastole tended to be lower in patients before pyridostigmine. In multivariate analyses adjusting for between-group differences in blood pressure, MG was no longer associated with lower longaxis function. Conventional echocardiographic measures of left ventricular diastolic and systolic function did not differ between groups. In conclusion, this study, using modern tissue Doppler imaging as well as conventional echocardiography, could not demonstrate definite MG-related cardiac involvement in a group of MG patients without known cardiac disease, but indicates that pyridostigmine-responsive MG-related alterations in cardiac muscle function exist in MG patients.