Ambulatory assessment of cardiac autonomic function in Chagas' heart disease patients based on indexes of R-R interval variation in the Valsalva maneuver.

1. The reflex cardiac autonomic function of Chagas' heart disease patients was evaluated by a simple, noninvasive 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 Valsalva maneuver was quantified in 33 outpatients with Chagas' cardiopathy without heart failure aged 38 +/- 9 years, and compared to 30 healthy control subjects aged 31 +/- 8 years (P greater than 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 which was recorded continuously from 10 s before to 90 s after the maneuver when the recovery phase had already started. 3. The chagasic group presented lower relative tachycardia (shortest R-R minus control R-R/control R-R) (-27.9 +/- 8.4%, mean +/- SD) and Valsalva ratio (longest R-R/shortest R-R) (1.67 +/- 0.3) than the control group (-34.2 +/- 6.5% and 1.93 +/- 0.3, respectively) (P less than 0.01). The time for maximum R-R interval variation (shortest R-R to longest R-R) was longer (18.0 +/- 7.2 s), and the velocity of this variation (longest R-R minus shortest R-R divided by shortest R-R/time for the maximum R-R variation) was lower (4.8 +/- 3.5%/s) in the chagasic patients (P less than 0.01) than in the controls (11.1 +/- 5.4 s and 10.8 +/- 6.0%/s, respectively). The mean relative bradycardia (longest R-R minus control R-R/control R-R) of the chagasic group (18.5 +/- 13.5%) was statistically similar (P greater than 0.05) to that of the control group (25.6 +/- 16.5%). 4. In 51% (17/33) of the chagasic patients, at least one significantly altered index was observed to exceed +/- 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 data show that varying degrees of cardiac autonomic dysfunction may be detected in a simple manner in ambulatory outpatients with Chagas' 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 denervation.(ABSTRACT TRUNCATED AT 400 WORDS)