Ambulatory assessment of cardiac autonomic function in chagas's heart disease patients based on indexes of R-R interval variation in the valsalva maneuver

RESUMO

1. The reflex cardiac autonomic function of Chagas' heart disease patients was evaluated by a simple, nonivasive and inexpensive ambulatory method as an alternative to the complex or invasive methods or drug tests hitherto used. Variations in the R-R interval during the Valsava maneuver was quantified in 33 outpatients with Chagas's cardiopathy without heart failure aged 38 ñ 9 yers, and compared to 30 healthy control subjects aged 31 ñ 8 years (P > 0.05). 2. Each subject carried out 3 to 4 Valsalva maneuvers in the supine position for 20 s at an intraoral pressure of 40 mmHg. Variations of R-R interval were calculated from the electrocardiogram whic was recorded continuously from 10 s before to 90 s after the maneuver when the recovery phase had alredy started. 3. The chagasic group presented lower relative tachycardia (shortest R-R minus control R-R/control R-R) (-27.9 ñ 8.4%, mean ñ SD) and Valsalva ratio (longest R-R/shortest R-R) (1.67 ñ 0.3) than the control group (34.2 ñ 6.5% and 1.93 ñ 0.3, respectively) (P < 0.01). The time for maximum R-R interval variation (shortest R-R to longest R-R) was longer (18.0 ñ 7.2s), and the velocity of this variations (longest R-R minus shortest R-R divided by shortest R-R/time for the maximum R-R variation) was lower (4.8 ñ3.5%/s) in the chagasic patients (P < 0.01) than in the controls (11.1 ñ 5.4 s and 10.8 ñ 6.0%/s, respectively). The mean relative bradycardia (longest R-R minus control R-R/control R-R) of the chagasic group (18.5 ñ 13.5%) was statistically similar (P > 0.05) to that of the control group (25.6 ñ 16.5%). 4. In 51% (17/33) of the chagasic patients, at least one significantly altered index was observed to exceed ñ 2 SD of the respective control mean, and for 3 of them (10% of the total) all the indexes were abnormal. In 49% (16/33) of the patients no abnormal index was observed. 5. These date show that varyng degress of cardiac autonomic dysfunction may be detected in a simple manner in ambulatory outpatients with Chagas's heart disease, with results similar to those obtained with application of complex or invasive tests. In all likelihood, the altered Valsalva R-R interval variation indexes in the present chagasic patients resulted from depressed parasympathetic activity on the heart consequent to the Chagas cardiac devervation. However, associated sympathetic dysfunction should not be ruled out as a possible secondary secondary cause