Retrospective evaluation of clinical parameters and survival characteristics in 137 dogs with reversed patent ductus arteriosus
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Background: Reversed patent ductus arteriosus (rPDA) is a comparatively rare form of canine congenital heart disease (CHD) and is defined by severe pulmonary arterial hypertension (PH), pulmonary-to-systemic shunting across a patent ductus arteriosus (PDA), caudal hypoxemia, and secondary erythrocytosis. These aberrations of normal structure and physiology dictate the phenotype of dogs with rPDA. To date, the veterinary literature contains a limited number of case reports and a single retrospective study of 43 dogs with rPDA. Objectives: This multi-center, retrospective descriptive study details patient characteristics, clinical signs, diagnostic findings, and survival data that typify rPDA in a large number of dogs. Animals: Dogs (n=137) diagnosed with rPDA by a board-certified cardiologist or a resident under the direct supervision of a board-certified cardiologist were retrospectively enrolled. Methods: Medical records of dogs diagnosed with rPDA between 5/1/1980 and 12/1/2019 were retrospectively reviewed at 19 centers in North America, Europe, and Asia. Demographic information and clinical data were collected and analyzed statistically. Results: Female dogs were overrepresented, accounting for 65 percent of the study population. Mean (+/- standard deviation) age at presentation was 29.1 months (+/-27.7). At the time of initial evaluation, 93 percent of dogs were exhibiting clinical signs, with exercise intolerance being most common. Right-sided congestive heart failure (rCHF) was diagnosed infrequently (15 percent). The mean maximum PCV was 66.6 percent (+/-12.0). Common echocardiographic findings included abnormal interventricular septal motion (88 percent), tricuspid valve regurgitation (69 percent), and right ventricular (RV) concentric hypertrophy (62 percent). Most dogs (67 percent) received a phosphodiesterase-V inhibitor (PDEVi), and phlebotomy was performed at least once in 41 percent of dogs. In bivariate survival analysis, the median survival time (MST; 95 percent confidence interval) was 90.6 months (74.4-121.9) for dogs that received a PDEVi versus 18.6 months (5.8-88.0) for those that did not (p= 0.008); 123.1 months (87.8-132.5) for those that received hydroxyurea versus 73.9 months (40.0-90.2) for those that did not (p= 0.008); and 112.4 months (74.4-129.1) for those that were treated with therapeutic phlebotomy versus 83.8 (36.9-90.2) for those that were not (p< 0.001). These factors remained significant predictors of survival in a multivariate analysis. Older age at presentation (p< 0.001), presenting PCV< 65 percent (p= 0.005), and absence of rCHF (p= 0.047) were also associated with improved survival in the multivariate analysis. Conclusions: The clinical, physical examination, and diagnostic findings associated with rPDA in 137 dogs were characteristic of severe pulmonary hypertension, chronic hypoxemia, and polycythemia. Phlebotomy, PDEVi therapy, and hydroxyurea, were associated with longer survival times. Conversely, survival times declined with rCHF and younger age at presentation.
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M.S.