Electrocardiography as the First Step for the Further Examination of Cardiac Involvement in Myasthenia Gravis

Introduction. Cardiac involvement of myasthenia gravis (MG) accompanies a poor prognosis. In the present study, we aimed to investigate the relationship between ECG abnormality and cardiac involvement. Methods. Of 178 patients diagnosed with MG between 2001 and 2013 at our hospital, we retrospectively analyzed consecutive 58 patients who underwent both ECG and echocardiography and without underlying cardiovascular disease. ECG abnormalities were defined by computer-assigned Minnesota-codes. Cardiac damage was defined as either (1) ejection fraction (EF) <55% on echocardiography or (2) elevated E/e′, the ratio of mitral velocity to early diastolic velocity of the mitral annulus >8 on echocardiography. Results. Thirty-three patients (56.8%) had ECG abnormality. An elevated E/e′ was observed in patients with ECG abnormality compared to those without ECG abnormality (11.2 ± 3.2, 8.7 ± 2.2, resp., p = 0.03). Among patients with ECG abnormality, 14 of 15 patients showed cardiac damage. Among patients without ECG abnormality, 6 of 33 patients showed cardiac damage (p = 0.003). Reduced EF was observed in five patients (8.6%) with ECG abnormality and none in patients without ECG abnormality. Conclusions. ECG may aid as the first step for the further examination of cardiac damage in patients with MG.