Active orthostatic stress and respiratory sinus arrhythmia in patients with Chagas' disease with preserved left ventricular global systolic function.
OBJECTIVE
To assess the use of the active orthostatic stress test for detecting vagal dysfunction in patients with Chagas' disease with preserved overall systolic function, and to compare it with the respiratory sinus arrhythmia test.


METHODS
Sixty-one chagasic patients (Ch) and 38 nonchagasic (NCh) patients with no significant evidence of heart disease or systemic diseases underwent Doppler echocardiography and autonomic function tests. The respiratory sinus arrhythmia test was performed through electrocardiographic recording during deep breathing, at 6 ripm, calculating the E:I ratio (mean ratio between the longest expiratory RR interval and the shortest inspiratory RR interval at each cycle). The electrocardiogram was recorded during the act of standing and during the following 30 seconds (active orthostatic stress test), and the max RR/min RR ratio (the longest and shortest RR intervals right after change in posture) was calculated. The indices were adjusted for significant covariables.


RESULTS
The max RR/min RR ratio (NCh: 1.52 [1.44-1.74] x Ch: 1.43 [1.33-1.51], P < 0.001) and the E:I ratio (NCh: 1.38 +/- 0.02 x Ch: 1.25 +/- 0.02, P<0.001) were lower among chagasic patients. A high correlation was observed between the adjusted max RR/min RR ratio and E:I ratio (r = 0.628, P < 0.001), but neither significantly correlated with left ventricular ejection fraction.


CONCLUSIONS
Chagasic patients with preserved left ventricular overall systolic function showed a significant reduction in the vagal indices obtained on short-lasting tests, as compared with normal controls. The active orthostatic stress test that, showed a good correlation with the respiratory sinus arrhythmia maneuver, constituted a valid option for the outpatient care assessment of vagal control.
Internal Medicine Department, Medical School of the UFMG, Belo Horizonte, MG, Brazil. tom@hc.ufmg.br
Antonio Luiz P
AL
Ribeiro
Lídia Magda
LM
Ferreira
Enilce de
Ed
Oliveira
Paulo C F
PC
Cruzeiro
Rosália Moraes
RM
Torres
Manoel Otávio Costa
MO
Rocha
D000293:Adolescent; D000328:Adult; D001146:Arrhythmia, Sinus / Q000175:diagnosis*; D016022:Case-Control Studies; D014355:Chagas Disease / Q000503:physiopathology*; D004244:Dizziness; D004562:Electrocardiography; D005080:Exercise Test; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013599:Systole; D014630:Vagus Nerve / Q000503:physiopathology*; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis*; D016277:Ventricular Function, Left / Q000502:physiology