Cardiovascular indicators and mitral valve disease in dogs with spontaneous hypercortisolism : prospective evaluation

Abstract

Background: Canine hypercortisolism (HC) is the most prevalent endocrinopathy in dogs in southern Brazil. The prognosis depends on several factors including the general health status, owners´ commitment, and the development of disease complications and comorbidities occurrence, such as cardiovascular complications including mitral valve disease (MVD), systemic arterial hypertension, and left ventricular hypertrophy. The main objective of the present study was to assess cardiovascular parameters in canine HC, based on investigating survival-related variables. The study also aimed to evaluate the influence of concurrent preclinical (MVD) on dogs` survival and the impact of HC on MVD progression. Materials, Methods & Results: A total of 25 dogs with spontaneous HC were enrolled and divided into 2 subgroups accordingly to their echocardiographic findings: group HC (normal echocardiography at first evaluation, n = 16); and group HC + MVD (concurrent presence of stages B1 and B2 MVD diagnosed at the first evaluation, n = 9). The patients were evaluated at diagnosis (T0); 6 months after treatment begging (T1); and after 12 months of treatment (T2). The owners were further contacted by phone or e-mail for 1 more year after T2 regarding survival information. A control group (CG, n = 20) was also evaluated at T0 and T1. At each evaluation, dogs were submitted to a complete clinical evaluation and physical exam, associated with a minimum database (CBC, serum biochemistry, and urine analysis) and cardiovascular evaluation composed of systolic blood pressure determination, electrocardiogram (ECG), and echodopplercardiography. In the HC group, 11/16 dogs underwent the evaluation at T2, while 4/9 dogs from the HC + MVD group and 17/20 dogs from the CG underwent the evaluation at T2. Five dogs (31.25%) from the HC group and 4 dogs (44.44%) from the HC + MVD group died before the end of the follow-up period. In the control group, only 1 dog (5.26%) died before the end of the study. Despite the higher mortality in the HC + MVD group during the follow-up period, there was no significant difference (P = 0.632) in survival when compared with the HC group. The MVD of 4 dogs included in the HC + MVD group was classified as stage B1, while the other 5 dogs were classified as stage B2. Only 1 dog from the CG developed stage B1 MVD in the period studied; however, progression of the MVD stage was documented in 1/4 of dogs in the HC + MVD group and MVD development was documented in 3/11 of dogs from the HC group from T0 to T2. The odds ratio (OR) and respective 95% confidence interval (95%CI) for HC as a risk factor for MVD progression were 4.267 (0.4268 - 42.65; P = 0.342). Exercise intolerance (12/16 dogs) and dyspnea (6/16 dogs) were the cardiorespiratory clinical signs with the highest incidence in the HC group at T0. When compared to the control group, both exercise intolerance (P < 0.001) and dyspnea (P = 0.03) occurrence were significantly higher in the HC group. The age (P = 0.001) and the occurrence of dyspnea (P = 0.036) at diagnosis were significantly higher in dogs with HC that died during the follow-up than those that remained alive. Regarding the occurrence of cardiac arrhythmias verified by ECG, no statistically significant differences were observed among groups. Discussion: The study suggests that systemic hypertension and altered echocardiographic measurements did not interfere with dogs’ survival; however, dyspnea was associated with a worse prognosis. Finally, it is possible to conclude that mitral valve degeneration is a common comorbidity in dogs with HC, however, it was not evidenced their interference in the survival of dogs with this endocrine disease or even a role of the HC in the progression of the MVD.