Dysautonomy in different death risk groups (Rassi score) in patients with Chagas heart disease.

Background: It has been difficult to prove that "catecholamine-induced cardiomyopathy" contributes to the mechanism of sudden cardiac death in Chagas heart disease. Also, it is almost impossible to rule out the possibility that it is not involved in the process. More importantly, the vagal-cholinergic pathway in the ventricle plays a direct role in the prevention of the initiation of complex ventricular arrhythmias, including nonsustained ventricular tachycardia, ventricular fibrillation responsible for sudden death.

Objective: To determine frequency of parasympathetic autonomic indices among the different groups of risk of cardiovascular death when stratified by Rassi score.

Methods: Patients with Chagas heart disease were selected and divided into three risk groups by Rassi score. A fourth group, non-Chagas group, was of similar age and gender. All were subjected to analysis of heart rate variability during controlled breathing (RSA) and tilt table passive test (tilt test). High frequency and low frequency/high frequency ratio were calculated and presented by box-plot. Also, t-test was used to compare the two groups.

Results: It was observed that the parasympathetic and sympathetic component were affected, when the risk group increased the response was worsened to the stimulus (RSA or Tilt). Also, the low-risk group was jeopardized, when compared to the non-Chagas group.

Conclusion: The loss of parasympathetic modulation was present in all Rassi risk groups, including the low risk, indicating that a morphological change of the myocardium represents a detectable neurofunctional change.