Study of heart rate variability in dogs with brachycephalic syndrome that underwent rhinoplasty

Abstract

Brachycephalic breeds possess higher vasovagal tone than do nonbrachycephalic breeds. Upper airway obstruction impairs the inspiratory effort by reducing the normal parasympathetic inhibition that occurs during this phase of the respiratory cycle. Sixteen dogs with nasal stenosis were included in this study, and an analytical and progressive analysis of the evolution of Heart Rate Variability (HRV) was performed at various time points: before the surgical procedure (day 0), and after the procedure on days 30 and 60. Surgical correction was performed using the vestibuloplasty technique, and HRV analysis was recorded via prolonged electrocardiography. Further, an analysis of the time domain indices was performed. Regarding clinical findings, an improvement in the average heart and respiratory rates after rhinoplasty, as well as a reduction in parasympathetic tone and resultant bradyarrhythmias were noted in all patients. Regarding the time domain HRV indices, Root-Mean of square sucessive NN interval difference (rMSSD) and Standard Deviation of all normal NN interval (SDNN) associated with the average heart rate, compared at different time points, strongly suggested that the reduction in parasympathetic stimulation was related to the reduction in HRV in these animals. The findings related to a reduction in the frequency of bradyarrhythmias corroborate the interpretative analysis of Lorenz graph indices, where there is a reduction in the cardiovagal index, without a significant alteration in the cardiosympathetic indices throughout the study period. The rMSSD index is the early-altered time-domain HRV index that can be used as an indicator of increase in parasympathetic activity caused by brachycephalic syndrome. The present study aimed to evaluate HRV through prolonged electrocardiographic examination, observing the excess of parasympathetic stimulation and the resultant bradyarrhythmias. In addition, evaluation of the clinical consequences of increased parasympathetic tone and the possibility of an improvement in autonomic balance following surgery, resulting in an improved quality of life and overall life expectancy in these patients, was performed.