Epidemiology of seropositive myasthenia gravis in Greece.

OBJECTIVES: To study the epidemiological characteristics of myasthenia gravis in Greece. METHODS: A population based study was carried out of seropositive myasthenia gravis in Greece for the period from 1 January 1983 to 30 June 1997; 843 patients were studied. RESULTS: The average annual incidence for the period 1992-7, for which the database is complete, was 7.40/million population/year (women 7.14; men 7.66). On 1 July 1997, there were 740 prevalent cases. The point prevalence rate was 70.63/million (women 81.58; men 59.39). The average overall annual mortality rate in the patients was 0.67/million population (women 0.53; men 0.82), and the mortality rate attributed to myasthenia gravis was 0.43/million population (women 0.41; men 0.45). The average age at onset was 46.50 years (women 40.16; men 54.46), and the mean age of the prevalent patients was 52.58 (women 47.65; men 59.48). The women:men incidence ratio was 1:1.04, and the prevalence ratio was 1.41:1. It is predicted that the prevalence and women: men prevalence ratio would increase if the patient list included all patients with a date of onset before 1983. CONCLUSIONS: The largest epidemiological study ever performed on myasthenia gravis is presented. The most important epidemiological indexes are provided.

Dispersion of ventricular repolarization is determined by the presence of myocardial viability in patients with old myocardial infarction. A dobutamine stress echocardiography study.

AIMS: The study sought to investigate the relationship of myocardial viability detected by dobutamine stress echocardiography to changes of QT dispersion and to the presence of arrhythmias during dobutamine infusion in patients with old myocardial infarction. We also examined whether patency of the infarct-related artery is associated with the presence of myocardial viability and QT dispersion. BACKGROUND: QT dispersion and myocardial variability have been associated with the presence of arrhythmias during late post infarction but not during dobutamine stress. Restoration of anterograde coronary flow has beneficial effects on ventricular systolic function and repolarization, suggesting that the extent of viable myocardium may determine ventricular repolarization. METHODS: Seventy five patients with previous myocardial infarction were studied in a low dose (up to 20 microg(-1) x kg(-1) x min(-1)) dobutamine stress echocardiography study. ECGs were obtained at rest and peak stress for measurement of QT intervals. The presence of ventricular arrhythmias (Lown grade >lb) during stress was noted. A reduction in the total wall motion score of the left ventricle at peak stress confirmed the presence of myocardial viability. RESULTS: Dobutamine infusion increased QT dispersion in all patients (P<0.01). Patients with myocardial viability had a lower resting QT dispersion (P<0.05) and a greater increase in QT dispersion% (P<0.01) than patients without. The combination of a resting QT dispersion <65 ms or an increase in QT dispersion >30% predicted viability with a sensitivity of 67%, a specificity of 96%, and an accuracy of 78%. A patent infarct-related artery, as well as ventricular arrhythmias, were more commonly observed in patients with evidence of viable myocardium (P<0.05). Patients with arrhythmias had a higher QT dispersion than patients without (P<0.05). CONCLUSION: The combination of a resting QT dispersion +/-65 ms or an increase in QT dispersion >30% predicts the presence of viable myocardium and thus, may represent a simple index for the assessment of viability in everyday clinical practice. Myocardial viability is related to a patent coronary artery and to a high incidence of arrhythmias accompanied by a greater increase in QT dispersion at peak dobutamine infusion.