Age-associated changes in the number of neurons in the right atrium

It has been demonstrated that chronotropic responses differ in healthy elderly subjects compared to those in younger normal adults. To evaluate the involvement of the autonomic nervous system, we determined the number of neurons in right atrial strips from six elderly individuals (aged 77 + or - 3.4 years) five of whom had died as the result of extracardiac causes, and from younger adult controls (aged 44.0 + or - 6.0 years) who had died in traffic accidents. There was a significant reduction in the number of neurons of the group of hearts from the elderly (3587 + or - 445, mean + or - SEM) compared with the control group (6412 + or - 377) of five hearts from younger adults (P<0.001). It is suggested that this decrease in the number of neurons contributes to the reduced chronotropic responses in the aged. The mechanisms responsible for the neuronal depopulation was not determined

Use of isometric exercise to demonstrate cardiac parasympathetic impairment in the digestive form of Chagas' disease

Standardized handgrip at 100% of maximal voluntary capacity was used to study heart rate responses to ismetric exercise in patients with the digestive form of Chagas" disease. The chronotropic responses of the group were significantly lower (P < 0.001) than tyhose exhibited by control subjects, and comparable to those observed in a group of cardiac chagasic patient. these results show that severe impairment of autonomic control of the heart may occur in chagasic patients apparently having only digestive tract involvement