Estudo do balanço simpatovagal e dos efeitos do pimobendan na variabilidade da frequência cardíaca de cães portadores de insuficiência cardíaca por doença valvar degenerativa crônica de mitral sob tratamento

Abstract

The heart rate variability (HRV) consist in a method able of assess the modulation of the autonomic nervous system (ANS) on the heart, allowing to determine possible simpatovagal changes. The analysis of time and frequency domain are types of signal processing used to investigate this variability, both dependent of the measures of RR intervals. The aim of this study was to evaluate the simpatovagal balance through HRV analysis by Holter method in dogs with valvar disease submitted to convencional drug therapy for heart failure or associate with Pimobendan. We used 37 adult dogs (13 males and 24 females), 03-14 years old and different breeds constituting 03 groups: CONT (healthy dogs without any treatment); CTP (dogs with heart failure receiving conventional therapy for CHF) and CTP + Pimo (dogs with heart failure receiving conventional therapy for CHF, associated with Pimobendan). The Holter examination was performed in different veterinary clinics in the Rio de Janeiro state, lasting 30 minutes and after a minimum period of 30 days from starting treatment. The parameters studied were: minimum heart rate; mean; maximum and QRS number. In the time domain were studied values: NN mean, SDNN, SDANN, SDNN index, rMSSD and pNN50. In the frequency domain the values studied were: Fc; HF; LF; VLF; LF / HF. Statistical values were showed as mean ± sem. The mean values of minimum heart rate, mean, maximum and QRS complex number of the different groups showed no statistical significance (P> 0.05). The mean values of the study of HRV in the time domain, the CTP and CTP + Pimo groups showed significant reduction (P <0.05) of the following parameters (SDNN; SDANN; SDNNIDX; RMSSD and pNN50) vs CONT group. In the heart rate variability in the frequency domain, CTP and CTP + Pimo groups showed significantly lower values of total power spectrum vs CONT (P <0.05); LF smaller values of CTP vs CONT group (P <0.05); larger values of LF of CTP + Pimo vs CTP group (P <0.05); smaller values of VLF of CTP + Pimo vs CONT group (P <0.01); lower values of LF / HF of CTP vs CONT group (P <0.05) and higher values to CTP + Pimo vs CTP group (P <0.01). Our study showed significant changes in HRV reduction in the time and frequency domains in CTP and CTP + Pimo groups when compared to CONT group. However, dogs treated with Pimobendan showed no significant evidence of improvement in their HRV parameters when compared to other dogs with heart failure that did not receive this drug, at least during the period proposed in this study. The changes in HRV parameters in dogs with heart failure were able to maintain even working with patients showing large breed diversity, of weights, sex and age; showing significant lower values in time and frequency domain when compared to normal dogs. The Pimobendan therapy, still no described in literature as able to influence HRV parameters in dogs with heart failure, in our study showed that animals treated with this drug showed larger sympathetic modulation, verified by LF/HF relation.