Variabilidade da frequência cardíaca em cães com degeneração mixomatosa valvar mitral

Abstract

The quantification of cardiac autonomic tone, through heart rate variability (HRV), has been used in several heart diseases of humans and animals in an attempt to establish the prognosis and risk of sudden death. However, in dogs with heart disease, there is no scientific consensus on the effect of the main cardiac disorders on HRV, which is often based on scientific studies or extrapolated from the findings observed in humans. Thus, the aim of the present study is to verify the effect of the most prevalent heart disease in dogs (myxomatous mitral valve degeneration) on HRV, through systematic review. For this purpose, the PubMed, Scielo and ScienceDirect databases were used to search for evidence, using the PICO acronym (Population = dogs with myxomatous valve degeneration; Intervention = HRV; Comparation = Non-intervention; Outcome = autonomic imbalance indicated by an increase in sympathetic tone and decrease in parasympathetic) that supported the scientific question. The search for data in the databases produced, summing the combinations between the search terms, a total of 1,805, 24 and 19,604 articles, respectively. After reading the titles, only seven studies were kept in the PubMed database, three in Scielo and one in ScienceDirect, which were subjected to reading the abstract as the last criterion of adequacy to the studied theme and exclusion, resulting in seven studies suitable to the scientific question. All studies were classified according to the levels of scientific evidence according to the Oxford Center for Evidence-based Medicine method, resulting in degrees of recommendation and levels that are represented by 28% B-2B and 72% B-3B, totaling the seven articles. The studies describe the change in HRV (decreased parasympathetic autonomic tone and increased sympathetic) in dogs with myxomatous mitral valve degeneration, who developed congestive heart failure (CHF). Thus, it is concluded that the disease is capable of influencing the HRV of dogs, well described from the occurrence of CHF, indicating a worse prognosis. However, there is a lack of evidence about HRV, especially in the early stages of the disease (asymptomatic phases), which requires further studies to understand the exact moment of the onset of this autonomic imbalance observed in dogs with CHF.