Estudo da variabilidade da frequência cardíaca em cães portadores da síndrome do braquicefálico submetidos à cirurgia de rinoplastia.

Abstract

The brachycephalic breeds have a higher vasovagal tonus index than non-brachycephalic dogs. The obstructive upper airway process impairs inspiratory work by reducing the normal parasympathetic inhibition of this phase of the respiratory cycle. The aim of the present study was to evaluate the HRV in the brachycephalic races, before and after surgical correction of the stenosis of the nostrils, by means of prolonged electrocardiography, observing the excess of the parasympathetic stimulation in relation to the occurrence of bradyarrhythmias and its clinical consequences, and the possibility of improving autonomic balancing after treatment, increasing the quality and life expectancy of these patients. Sixteen dogs with nostril stenosis were included, where the analysis and progression of the HRC findings at different moments before the surgical procedure (day 0) and after the procedure were performed in two moments, 30 and 60 days. Surgical correction was performed by means of the alavestibulplasty technique and HRV analysis was recorded by means of prolonged electrocardiography. For this examination, the indexes were analyzed in the time domain. Regarding the clinical findings, there was an improvement in the evaluation of the heart and respiratory rate after the rhinoplasty surgery, as well as a reduction of the parasympathetic activity under the Autonomic Nervous System (ANS), in which the bradyarrhythmias in all patients are repeated. Regarding HRV indexes in the time domain, rMSSD (Root-Mean of square sucessive NN interval difference) and SDNN (Standard Deviation of all normal NN interval) associated with mean heart rate findings, compared at different times, have provided strong evidence that the reduction of parasympathetic stimulation is related to the reduction of HRV in these animals. The findings related to the reduction of bradyarrhythmias corroborate the interpretive analysis of the indices of the Lorenz chart, where there is a reduction of the cardiovagal index, without a significant change in the cardiosympathetic indexes throughout the study. The rMSSD is the HRV index in the time domain that can be used as an indicator of the increase in parasympathetic activity caused by Brachycephalic Syndrome (BS).