RESUMO
INTRODUCTION: According to the current literature on the subject, patients with syncope suffer a dysfunction of the autonomic nervous system (ANS). Yet few studies offer a clear explanation of this dysfunction. Moreover, the evaluation of cardiovascular reflexes is a simple, useful method of studying the functional status of the ANS. This work was designed to evaluate the existence of dysautonomia in syncope patients by means of the autonomic cardiovascular stimulation tests; it has been the most comprehensive of those published to date. SUBJECTS AND METHODS: We studied 170 healthy volunteers and 188 patients with syncopes in the previous months, paired by age and sex. Cardiovascular stimulation tests were conducted, in accordance with Ewing and Clark's methodology, together with the cold test. A rating scale was included to evaluate the symptoms related to ANS involvement. RESULTS: Syncope patients display lower reactivity in tests involving cardiovascular stimulation of the ANS, regardless of whether they are taken individually or as a whole (67% in patients and 39% in controls) (p = 0.0001), except in the cold test. They also show an increase in the clinical symptoms of an autonomic origin (2.82 +/- 0.17) with respect to control subjects (0.78 +/- 0.09) (p = 0.0001). CONCLUSIONS: Our syncope patients have a dysautonomia that appears as a sympathetic and parasympathetic hypofunction. These findings confirm the value of autonomic cardiovascular stimulation tests in the study of these patients. Moreover, the search for other symptoms of autonomic involvement can be a great aid in evaluating this pathology.