Effect of pimobendan on the incidence of arrhythmias in small breed dogs with myxomatous mitral valve degeneration.

OBJECTIVE: To determine if pimobendan, a phosphodiesterase III inhibitor and calcium sensitizer with positive survival benefits, has an effect on incidence of arrhythmias compared to placebo in small breed dogs with congestive heart failure (CHF) due to myxomatous mitral valve degeneration (MMVD). ANIMALS: Eight client-owned small breed dogs (<15 kg) with CHF due to MMVD. METHODS: A prospective double-blind randomized placebo-controlled crossover study design was used. Data were recorded at baseline and 2 weeks post-administration of placebo or pimobendan. Average heart rate and incidence of arrhythmia were determined from 24 h Holter analysis. Owners completed a quality of life (QOL) questionnaire at each time point and recorded sleeping respiratory rates (SRR). Mixed effects analysis of variance, with dog as the random variable was used to compare values obtained between baseline, placebo, and pimobendan. RESULTS: Compared to baseline, QOL scores were significantly improved following administration of either placebo or pimobendan (p = 0.021 and p < 0.001, respectively). No significant differences in type or incidence of supraventricular or ventricular arrhythmia were identified. Average heart rate with pimobendan was significantly lower than baseline (p < 0.001). Compared to baseline, SRR was significantly lower with pimobendan (p = 0.004), and significantly different from placebo (p = 0.045). CONCLUSIONS: No significant difference between pimobendan and placebo was found on incidence of supraventricular or ventricular arrhythmia. The decrease in average heart rate and SRR may be reflective of superior heart failure control achieved with pimobendan therapy.

Fossa ovalis tear causing right to left shunting in a Cavalier King Charles Spaniel.

Left atrial tear is an infrequent sequela of severe mitral regurgitation due to myxomatous mitral valve degeneration. Interatrial septal tear due to mitral regurgitation causing a left-to-right shunt is uncommon. Right to left shunting secondary to acute interatrial septal tear is very rarely reported in the human literature, and has not been reported in the veterinary literature in a dog. This case describes the clinical, radiographic, echocardiographic, gross pathologic, and histopathologic features of a dog presented in acute respiratory distress secondary to acute onset right to left shunting through the interatrial septum. This was later documented to be due to a tear in the septum secondary to tricuspid regurgitation and pulmonary hypertension. The presence of an acquired right to left shunting atrial septal defect is of clinical and prognostic significance, and should be considered in cases of acute respiratory distress.

Aortic thrombosis in dogs: 31 cases (2000-2010).

OBJECTIVE: To describe clinical signs, treatment, and outcome of aortic thrombosis in dogs. DESIGN: Retrospective case series. ANIMALS: 31 dogs with aortic thrombosis. PROCEDURES: Records were retrospectively reviewed and data collected regarding signalment, historical signs, physical examination findings, laboratory testing, definitive diagnosis, and presence of concurrent disease. RESULTS: The records of 31 dogs with clinical or postmortem diagnosis of aortic thrombosis were reviewed. Onset of clinical signs was acute in 14 (45%) dogs, chronic in 15 (48%), and not documented in 2 (6%). Femoral pulses were subjectively weak in 6 (19%) dogs and absent in 17 (55%). Frequent laboratory abnormalities included high BUN concentration (n = 13), creatinine concentration (6), creatine kinase activity (10), and D-dimer concentration (10) and proteinuria with a urine protein-to-creatinine concentration ratio > 0.5 (12). Concurrent conditions included neoplasia (n = 6), recent administration of corticosteroids (6), and renal (8) or cardiac (6) disease. Median survival time was significantly longer for dogs with chronic onset of disease (30 days; range, 0 to 959 days) than for those with acute onset of clinical signs (1.5 days; range, 0 to 120 days). CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that aortic thrombosis is a rare condition in dogs and accounted for only 0.0005% of hospital admissions during the study period. The clinical signs for dogs with aortic thrombosis differed from those seen in feline patients with aortic thromboembolism. Median survival time was significantly longer for dogs with chronic disease than for dogs with acute disease. Despite treatment, outcomes were typically poor, although protracted periods of survival were achieved in some dogs.