Functional alterations of the autonomic nervous system in Chagas' heart disease

Abstract

Several independent pathological studies in experimental models and in human beings showed conspicuous autonomic denervation in Chagas' disease. In spite of the inherently complex structural organization of the autonomic nervous system, the parasympathetic and sympathetic divisions are involved, as shown by many functional studies. Hence, Chagas' disease represents a unique model of impairment of the autonomic control of the heart, in absence of the nonspecific effects of cardiac failure. An important limitation of the studies thus far carried out is the lack of a better knowledge of the molecular biology characteristics of different strains of T. cruzi. This could explain some geographical discrepancies found in the clinical behaviour of Chagas' disease, and contribute to a better understanding of its pathophysiology.

Estresse ortostático ativo e arritmia sinusal respiratória em chagásicos com função sistólica global do ventrículo esquerdo preservada

“…However, we know no report about the use of the max:min RR ratio for detecting vagal dysfunction in Chagas' disease on an outpatient care basis. The active orthostatic stress test is sensitive, specific, reproducible, and easily performed, being con- Table I The results of the active orthostatic stress test in chagasic patients with no heart disease, as compared with that in normal controls, confirm the findings of our previous study performed in the same group of patients [4][5][6] , and in another sample later studied 7,8 , and also the findings reported by other authors [24][25][26][27] . The different methods used, such as the variability in heart rate (assessed with different techniques) 5,7,8,22 , the Valsalva maneuver 6,23,24,26 , and respiratory sinus arrhythmia 5,26 , showed that autonomic dysfunction is present in patients with no evidence of heart disease and with preserved left ventricular function.…”

Chagas heart disease: pathophysiologic mechanisms, prognostic factors and risk stratification

“…Consistent with anatomic parasympathetic denervation, abnormal autonomic cardiac regulation has been shown in many functional investigations, even before the development of ventricular dysfunction (Ribeiro et al 2001). Because of the dysautonomia, chagasic patients are deprived of the tonic inhibitory action normally exerted by the parasympathetic system on the sinus node and they also lack the vagally mediated mechanism to respond to transient changes in blood pressure or venous return by using quick-onset bradycardia or tachycardia (Amorim & Marin-Neto 1995). However, several conceptual obstacles have challenged the applicability of the neurogenic theory (Marin-Neto et al 2007).…”

Chagas' heart disease

“…Although not yet used for clinical purposes, this method has the potential to show the underlying myocarditis and also may provide accurate anatomic and functional characterization of cardiac involvement 74 Cardiac autonomic assessment -Cardiac autonomic dysfunction, mainly parasympathetic, can be shown in chagasic patients (including those with isolated digestive disease) whose heart response to several autonomic tests (including the RR variability measurement) is impaired, as compared to control subjects 47,75,76,77 . However, these abnormalities are neither correlated with any symptoms, nor cause postural hypotension.…”

“…Correspondent striking abnormalities of parasym-pathetic and, to a lesser extent, of sympathetic cardiac autonomic control have been clearly documented by extensive laboratory investigation in humans 47,69,[75][76][77]96 . This aspect seems to be a hallmark of this disease.…”

“…Thus, the frequency and the intensity of this abnormality are quite variable, and a mismatch between the presence of autonomic denervation and ventricular dysfunction is often seen 77,92,96,[101][102][103] . Differences in T. cruzi strain and/or regional environment are likely causes for variable neurotropism observed in several regions 99 .…”