RESUMO
Continuous 24 hour electrocardiography (Holter method) was carried out during work time in 64 workers. They were divided into two groups: the first group comprised 34 subjects with either organic heart disease (coronary artery disease, valvular heart disease, operated coarctation, hypertrophic cardiomyopathy) or a documented arrhythmia without proven underlying cardiac disease; the second group comprised 30 subjects without known cardiac disease but complaining of symptoms suspected to be of cardiac origin or with isolated electrocardiographic abnormalities. At the end of the study we concluded that Holter monitoring is possible in subjects performing physical occupations even in difficult conditions. The trends of heart rate, especially mean heart rate calculated over 10 minute periods, confirmed the relationship between heart rate and the intensity of the physical activity. Atrial extrasystoles and episodes of supraventricular tachycardia were as common in the first as in the second group (20% and 18% respectively). This did not apply to ventricular extrasystoles: they were observed in both groups but were significantly more common in the first group (55% compared to 33%); ventricular extrasystoles, usually of a single configuration and isolated, were more common in the first group, especially amongst the coronary patients. Sinus node dysfunction was only observed in the second group (12.5%), in young subjects, and this occurred with only one exception at night. These findings support previous reports in the literature. However, the interpretation of these results is difficult because of the absence of well established normal values.