Introduction:

Patients with Down syndrome without structural heart disease may present with a dysfunction of the cardiac autonomic regulation, which is manifested by a reduced response of the heart rate (HR) to stimuli. Based on the hemodynamic responses, it has been postulated that individuals with Down syndrome have a reduced vagal tone and sympathetic activation. This review explains the role of the autonomic system in the control of HR and the attenuated chronotropic response observed in this population.

Objective:

To describe, through a clinical case presentation, the autonomic dysfunction observed in patients with Down syndrome, in order to identify the causes attributed by scientific evidence.

Materials and methods:

A clinical case was described and a search was made in PubMed of the terms: "Down Syndrome" AND "Bradycardia", "VO2peak", "Heart Rate Variability", "Vagal Tone", "Sympathetic Activation".

Results:

The findings suggest that physical exercise may be an effective intervention to improve autonomic cardiac function in patients with Down syndrome. Furthermore, training-induced improvements were achieved by participants with lower levels of vagal modulation at the start of the study, in both patients with and without disabilities. In consequence, training may be effective to improve cardiorespiratory fitness in those who have a greater degree of autonomic dysfunction.

Conclusion:

A clinical case of Down syndrome with sinus dysfunction was presented in this study. This condition could be related to a dysfunction of autonomic cardiac function regulation caused by reduced HR response to stimuli.

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