Aortocavitary fistula secondary to vegetative endocarditis in a rabbit

Ruptured left sinus of Valsalva aneurysm into the left atrium in a dog

A dog with immune-mediated thrombocytopenia and a new heart murmur had an echocardiogram in 2016 and was found to have a suspected aorto-left atrial fistula. The echocardiogram findings remained relatively static from 2016 to 2022. This report highlights the use of cardiac-gated computed tomography angiography to allow further understanding of a complex anomaly in a patient with a ruptured sinus of Valsalva aneurysm causing a fistulous connection with the left atrium.

Spontaneous rupture of the right aortic sinus resulting in a sterile aorto-atrial fistula in a pet rabbit (Oryctolagus cuniculus)

Aortocardiac fistula is a broad term used to describe defects between the aorta and other cardiac chambers that can occur in humans and animals. A 1.5-year-old, 1.7 kg, male castrated Holland lop rabbit (Oryctolagus cuniculus) was presented for a two-week history of a heart murmur with corresponding cardiomegaly on radiographs. Physical examination confirmed a grade-V/VI continuous heart murmur on the right sternal border with a regular rhythm and a gallop sound. Echocardiography revealed an aortic-to-right-atrial fistula causing severe left-sided volume overload. Based on the echocardiographic findings, rupture of the right aortic sinus was suspected. Due to the poor prognosis, euthanasia was elected. On necropsy, a fistula was found connecting the right aortic sinus with the right atrium, without evidence of an inflammatory response nor evidence of an infectious etiology. The sudden onset of a heart murmur supported acquired fistulation from a ruptured aortic sinus (also known as the sinus of Valsalva), though a congenital malformation could not be completely excluded.

Pharmacokinetics of pimobendan following oral administration to New Zealand White rabbits (Oryctolagus cuniculus)

OBJECTIVE

To determine the pharmacokinetics and potential adverse effects of pimobendan after oral administration in New Zealand White rabbits (Ocytolagus cuniculi).

ANIMALS

10 adult sexually intact (5 males and 5 females) rabbits.

PROCEDURES

2 pilot studies were performed with a pimobendan suspension or oral tablets. Eight rabbits received 7.5 mg of pimobendan (mean 2.08 mg/kg) suspended in a critical care feeding formula. Plasma concentrations of pimobendan and O-demethylpimobendan (ODMP) were measured, and pharmacokinetic parameters were calculated for pimobendan by noncompartmental analysis. Body weight, food and water consumption, mentation, urine, and fecal output were monitored.

RESULTS

Mean ± SD maximum concentration following pimobendan administration was 15.7 ± 7.54 ng/mL and was detected at 2.79 ± 1.25 hours. The half-life was 3.54 ± 1.32 hours. Plasma concentrations of pimobendan were detectable for up to 24 hours. The active metabolite, ODMP, was detected in rabbits for 24 to 36 hours. An adverse event occurred following administration of pimobendan in tablet form in 1 pilot study, resulting in death secondary to aspiration. No other adverse events occurred.

CLINICAL RELEVANCE

Plasma concentrations of pimobendan were lower than previously reported for dogs and cats, despite administration of higher doses, and had longer time to maximum concentration and half-life. Based on this study, 2 mg/kg of pimobendan in a critical care feeding formulation should maintain above a target plasma concentration for 12 to 24 hours. However, further studies evaluating multiple-dose administration as well as pharmacodynamic studies and clinical trials in rabbits with congestive heart failure are needed to determine accurate dose and frequency recommendations.

Clinical and pathological findings in rabbits with cardiovascular disease: 59 cases (2001-2018)

OBJECTIVE

To determine epidemiological features of cardiovascular disease in rabbits examined at a veterinary teaching hospital and characterize clinical and pathological findings.

ANIMALS

59 rabbits.

PROCEDURES

Medical records from 2001 to 2018 were reviewed, and data were collected. Echocardiographic images and histologic diagnoses were reviewed.

RESULTS

The prevalence of cardiovascular disease was 2.6% (59/2,249). Clinical signs related to cardiac disease included heart murmur (n = 25 rabbits), arrhythmia (22), tachypnea or dyspnea (13), hyporexia or anorexia (13), and muscle wasting (9). Radiographic (n = 39) abnormalities included cardiomegaly (19) and peritoneal (12) and pleural (11) effusion. Common echocardiographic (n = 37) diagnoses included degenerative valve disease (15), dilated cardiomyopathy (7), unclassified cardiomyopathy (4), restrictive cardiomyopathy (3), and hypertrophic cardiomyopathy (2). On ECG (n = 19), supraventricular arrhythmias (16) were more common than ventricular arrhythmias (12). Thirty-five necropsy reports were available, and diagnoses included cardiomyopathy (n = 14), myocarditis (10), and arteriosclerosis (9). Medical management (n = 20) included a wide range of drugs and dosages with few adverse effects. Survival times (n = 36 rabbits) ranged from 1 to 2,353 days with a median cardiac disease-specific survival time of 306 days.

CONCLUSIONS AND CLINICAL RELEVANCE

The findings provided information on the prevalence of cardiovascular disease in rabbits and survival times for affected rabbits. Right-sided, left-sided, and biventricular congestive heart failure occurred equally. Median survival time was lower than that reported for other species. Further research on the diagnosis and treatment of cardiovascular disease in rabbits is needed.

Cardiovascular Disease

Cardiac disease is increasingly diagnosed in pet rabbits, presumably because of their lengthening life span and the increased sophistication of their veterinary care. However, relatively little is known about the origins of and therapy for cardiac disease in pet rabbits. Dyspnea, murmurs, and arrhythmias are common clinical signs in rabbits with cardiac disease. However, rabbits with congestive heart failure may hide signs of illness until the disease has become severe. Unique physiologic characteristics (e.g., obligate nasal breathing and limited collateral circulation to the myocardium) predispose rabbits to collapse from stress and oxygen deprivation; therefore, oxygen supplementation and stabilization are priorities for the rabbit presenting in cardiorespiratory distress. The diagnostic workup for cardiac disease in rabbits is very similar to that for traditional pets and involves radiography, electrocardiography, and echocardiography. Cardiomyopathy and valvular degeneration are relatively common forms of cardiac disease in rabbits, while congenital anomalies are rare. Use and dosing of therapeutic agents is extrapolated from dogs and cats. Spontaneous arteriosclerosis is prevalent in rabbits, with an historical incidence of up to 40% in large breeds.

Adipose-Derived Stem Cells Are an Efficient Treatment for Fistula-in-ano of Japanese Rabbit

Fistula-in-ano (FIA, anal fistula) treatment remains a surgical challenge for coloproctologists. Adipose tissue-derived stem cells (ADSCs) are a new frontier in the treatment of FIA. In this study, we established a FIA model of Japanese rabbit and evaluated the effect of four treatments on fistula healing: ADSC transplantation, acellular small intestinal submucosa (ASIS), noncutting seton, and PBS as negative control. High-throughput RNA sequencing was also performed to investigate the anal tissue (normal and ADSC treatment group) expression profile of mRNA. Our data showed that ADSC treatment had the shortest time to promote fistula healing compared to the other treatments, and fistula filled with new adipose tissue and muscle cells without scar. Gene Ontology (GO) analysis of RNA-seq data showed that the differential genes are enriched in system development and animal organ development. Taken together, our findings demonstrate that ADSCs rapidly promote fistula healing through differentiation, a promising stem cell therapy for FIA. The rabbit is an effective animal model for evaluating FIA therapeutic options.