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Abstract

Objective—To determine clinical features of dilated cardiomyopathy (DCM) in Great Danes and to determine whether DCM is familial in this breed.

Design—Retrospective study.

Animals—17 Great Danes with DCM.

Procedure—Medical records of Great Danes in which DCM was diagnosed on the basis of results of echocardiography (fractional shortening < 25%, endsystolic volume index > 30 ml/m2 of body surface area) were reviewed. Pedigrees were obtained for affected animals, as well as for other Great Danes in which DCM had been diagnosed.

Results—Dilated cardiomyopathy appeared to be familial and was characterized by ventricular dilatation, congestive heart failure (left-sided or biventricular), and atrial fibrillation. Pedigree analysis suggested that DCM was inherited as an X-linked recessive trait, but the mode of inheritance could not be definitively identified.

Conclusions and Clinical Relevance—Results suggest that DCM may be an X-linked recessive trait in Great Danes. Thus, dogs with DCM probably should not be used for breeding, and female offspring of affected dogs should be used cautiously. Male offspring of affected females are at an increased risk of developing DCM and should be evaluated periodically for early signs of disease. Results of pedigree analysis were preliminary and should be used only as a guide for counseling breeders, rather than as a basis for making breeding decisions. (J Am Vet Med Assoc 2001;218:729–732)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the usefulness of echocardiography in the diagnosis of heartworm disease in cats and to compare this modality with other tests.

Design—Retrospective study.

Animals—43 cats with heartworm infection that had echocardiographic examinations at 2 veterinary teaching hospitals between 1985 and 1997. Twenty-two of these 43 cats also underwent radiography of the thorax and heartworm antibody and heartworm antigen testing.

Procedure—Cats were determined to be infected with Dirofilaria immitis infection on the basis of 1 or more of the following findings: positive modified Knott or antigen test result, echocardiographic evidence of heartworm disease, or confirmation of the disease on postmortem examination. The percentage of echocardiographs in which heartworms were evident was compared with the percentage of radiographs in which pulmonary artery enlargement was evident and results of antigen or antibody tests in cats in which all tests were performed.

Results—Overall, heartworms were detectable by use of echocardiography in 17 of 43 cats, most often in the pulmonary arteries. In the 22 cats in which all tests were performed, antibody test results were positive in 18, antigen test results were positive in 12, and pulmonary artery enlargement was evident radiographically and heartworms were identifiable echocardiographically in 14. Heartworm infection was diagnosed exclusively by use of echocardiography in 5 cats in which the antigen test result was negative.

Conclusions and Clinical Relevance—Although echocardiography was less sensitive than antigen testing, it was a useful adjunctive test in cats that had negative antigen test results in which there was a suspicion of heartworm disease. The pulmonary arteries should be evaluated carefully to increase the likelihood of detection of heartworms echocardiographically. ( J Am Vet Med Assoc2001;218:66–69)

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine whether plasma concentrations of tumor necrosis factor-α (TNF-α) are increased in cats with congestive heart failure (CHF) secondary to cardiomyopathy.

Animals—26 adult cats with CHF and cardiomyopathy and 9 healthy control cats.

Procedure—Plasma concentrations of TNF-α were measured in cats with CHF and cardiomyopathy. Tumor necrosis factor-α was measured by quantifying cytotoxic effects of TNF-α on L929 murine fibrosarcoma cells.

Results—Concentrations of TNF-α were increased (0.13 to 3.6 U/ml) in 10 of 26 cats with CHF but were undetectable in the other 16 cats with CHF and all control cats. In 20 of 26 cats with CHF, right-sided heart failure (RHF) was evident; TNF-α concentrations were increased in 9 of these 20 cats. The remaining 6 cats had left-sided heart failure (LHF); TNF-α concentrations were increased in only 1 of these cats. Age of cats with LHF (mean ± SD, 12.1 ± 6.2 years) was not significantly different from age of the cohort with RHF (10.5 ± 5.2 years). Body weight of cats with increased TNFα concentrations (5.4 ± 1.8 kg) was not significantly different from body weight of cats with CHF that did not have measurable concentrations of TNF-α (4.7 ± 1.6 kg).

Conclusionss and Clinical Relevance—Concentrations of TNF-α were increased in many cats with CHF. Cats with RHF were most likely to have increased TNF-α concentrations. Increased plasma concentrations of TNF-α in cats with CHF may offer insights into the pathophysiologic mechanisms of heart failure and provide targets for therapeutic interventions. (Am J Vet Res 2002;63:640–642)

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in American Journal of Veterinary Research

Abstract

Objective—To determine the pharmacokinetics of carvedilol administered IV and orally and determine the dose of carvedilol required to maintain plasma concentrations associated with anticipated therapeutic efficacy when administered orally to dogs.

Animals—8 healthy dogs.

Procedures—Blood samples were collected for 24 hours after single doses of carvedilol were administered IV (175 µg/kg) or PO (1.5 mg/kg) by use of a crossover nonrandomized design. Carvedilol concentrations were detected in plasma by use of high-performance liquid chromatography. Plasma drug concentration versus time curves were subjected to noncompartmental pharmacokinetic analysis.

Results—The median peak concentration (extrapolated) of carvedilol after IV administration was 476 ng/mL (range, 203 to 1,920 ng/mL), elimination half-life (t1/2) was 282 minutes (range, 19 to 1,021 minutes), and mean residence time (MRT) was 360 minutes (range, 19 to 819 minutes). Volume of distribution at steady state was 2.0 L/kg (range, 0.7 to 4.3 L/kg). After oral administration of carvedilol, the median peak concentration was 24 µg/mL (range, 9 to 173 µg/mL), time to maximum concentration was 90 minutes (range, 60 to 180 minutes), t1/2 was 82 minutes (range, 64 to 138 minutes), and MRT was 182 minutes (range, 112 to 254 minutes). Median bioavailability after oral administration of carvedilol was 2.1% (range, 0.4% to 54%).

Conclusions and Clinical Relevance—Although results suggested a 3-hour dosing interval on the basis of MRT, pharmacodynamic studies investigating the duration of β-adrenoreceptor blockade provide a more accurate basis for determining the dosing interval of carvedilol. (Am J Vet Res 2005;66:2172–2176)

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in American Journal of Veterinary Research

Abstract

Objective—To devise a technique for gradual occlusion of the caudal vena cava in dogs and determine effects of complete occlusion of the caudal vena cava.

Animals—8 mixed-breed hounds that weighed between 25 and 30 kg.

Procedure—Baseline evaluation of dogs included serum biochemical analyses and determination of glomerular filtration rate (GFR) with dynamic renal scintigraphy and plasma clearance analysis. An occluder was placed around the vena cava in the region cranial to the renal veins. The occluder was attached to a vascular access port. The vena cava was gradually occluded over 2 weeks. The GFR was measured every 2 weeks after surgery, and venograms were performed every 3 weeks after surgery. Blood samples were collected every 48 hours for the first week and then weekly thereafter to measure BUN and creatinine concentrations and activities of alanine transaminase, alkaline phosphatase, and creatinine kinase. Dogs were euthanatized 6 weeks after surgery, and tissues were submitted for histologic examination. The GFR and biochemical data were compared with baseline values.

Results—Gradual occlusion of the caudal vena cava was easily and consistently performed with this method, and adverse clinical signs were not detected. Formation of collateral vessels allowed overall GFR to remain constant despite a decrease in function of the left kidney. Measured biochemical values did not deviate from reference ranges.

Conclusions and Clinical Relevance—Gradual occlusion of the caudal vena cava may allow removal of adrenal gland tumors with vascular invasion that would otherwise be difficult or impossible to resect. (Am J Vet Res 2003;64:1347–1353)

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in American Journal of Veterinary Research

Abstract

Objective—To report the outcome of minimally invasive surgical treatment of heartworm caval syndrome in a series of dogs and to provide information on long-term survival of patients with this condition.

Design—Retrospective case series.

Animals—42 client-owned dogs with a diagnosis of heartworm caval syndrome.

Procedures—Information on history, clinical, laboratory, and diagnostic imaging findings and treatment was obtained from medical records. When possible, additional follow-up information was obtained through telephone interviews with referring veterinarians and owners.

Results—Of the 42 dogs with caval syndrome, 21 underwent minimally invasive surgical treatment consisting of transvenous heartworm extraction. Two of the 21 dogs died during the procedure, and after surgery, 4 died. Following induction of anesthesia, heartworms migrated into the distal portion of the pulmonary artery in 1 dog; therefore, extraction was not attempted. Transvenous heartworm extraction was completed successfully in 14 dogs, and all 14 of these dogs were discharged from the hospital. Mean follow-up time in these 14 dogs was 24.4 ± 17.7 months with a range of 2 to 56 months. At the time of final follow-up, 10 of these 14 dogs had survived at least 18 months and 7 had survived > 24 months. By the end of the study, 1 dog was lost to follow-up and 3 had been euthanatized for unrelated reasons.

Conclusions and Clinical Relevance—Results of the study reported here suggest that dogs with caval syndrome that undergo successful transvenous heartworm extraction and survive to discharge have a good long-term prognosis.

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in Journal of the American Veterinary Medical Association

Abstract

Case Description—A 3-year-old sexually intact male Standard Poodle was admitted to the veterinary teaching hospital for transcatheter closure of a large atrial septal defect (ASD).

Clinical Findings—The dog had exercise intolerance and was thin. Findings on physical examination were within normal limits with the exception of a left base systolic heart murmur (grade 5/6). The dog was not receiving any medications. Echocardiography and thoracic radiography confirmed the diagnosis of ASD and revealed compensatory changes consistent with a large left to right shunting ASD. Results of serum biochemical analysis and CBC were within reference range limits.

Treatment and Outcome—Transcatheter ASD closure with an atrial septal occluder (ASO) was performed and failed. An open heart surgical approach under cardiopulmonary bypass was declined by the dog's owners. The dog underwent a novel hybrid approach involving active device fixation under temporary inflow occlusion after transatrial device deployment. The dog recovered with some manageable postoperative complications. As of the last follow-up examination, the dog had 10 months of event-free survival.

Clinical Relevance—Transcatheter closure by use of an ASO and open heart patch repair with cardiopulmonary bypass to surgically treat dogs with ASD has been reported. Transcatheter closure is not possible in dogs with large ASD. The novel hybrid procedure reported herein represented a viable alternative to euthanasia.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the effect of PO administration of pimobendan on clinical and echocardiographic variables and survival time in cats with heart failure characterized by ventricular systolic dysfunction.

Design—Retrospective cohort study.

Animals—27 client-owned cats (16 male and 11 female) with heart failure, treated with pimobendan (mean ± SD dosage, 0.26 ± 0.08 mg/kg [0.118 ± 0.036 mg/lb], PO, q 12 h).

Procedures—Information on medical history, laboratory results, diagnostic imaging findings, treatments received, and survival time were obtained from medical records of cats that received pimobendan because of cardiac disease. When possible, additional follow-up information was obtained through telephone interviews with referring veterinarians and owners.

Results—The mean ± SD age of all 27 cats was 8.9 ± 5.2 years. All cats had received several cardiac medications. Types of heart disease represented included unclassified cardiomyopathy (CM; n = 11 [41%]), dilated CM (8 [30%]), arrhythmogenic right ventricular CM (4 [15%]), congenital heart disease (3 [11 %]), and hypertrophic CM with regional hypokinesis (1 [4%]). All cats had ventricular systolic dysfunction. One cat with systolic anterior motion of the mitral valve became severely hypotensive after initial administration of pimobendan and was excluded from the survival analysis. Median survival time was 167 days (95% confidence interval, 32 to 339 days).

Conclusions and Clinical Relevance—Pimobendan appeared to be well tolerated in cats with heart failure characterized by ventricular systolic dysfunction of various etiologies. Cats with systolic anterior motion of the mitral valve may develop systemic hypotension when treated with pimobendan. Additional studies are needed to establish dosages for pimobendan and its effects before it can be recommended for treatment of cats with CHF.

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in Journal of the American Veterinary Medical Association

Abstract

Objective—To identify clinical, echocardiographic, and electrocardiographic abnormalities in Boxers with cardiomyopathy and echocardiographic evidence of left ventricular systolic dysfunction.

Design—Retrospective study.

Animals—48 mature Boxers.

Procedure—Medical records were reviewed for information on age; sex; physical examination findings; and results of electrocardiography, 24-hour ambulatory electrocardiography, thoracic radiography, and echocardiography.

Results—Mean age of the dogs was 6 years (range, 1 to 11 years). Twenty (42%) dogs had a systolic murmur, and 9 (19%) had ascites. Congestive heart failure was diagnosed in 24 (50%) dogs. Seventeen (35%) dogs had a history of syncope. Mean fractional shortening was 14.4% (range, 1% to 23%). Mean left ventricular systolic and diastolic diameters were 4.5 cm (range, 3 to 6.3 cm) and 5.3 cm (range, 3.9 to 7.4 cm), respectively. Twenty-eight (58%) dogs had a sinus rhythm with ventricular premature complexes (VPCs), and 20 had supraventricular arrhythmias (15 with atrial fibrillation and 5 with sinus rhythm and atrial premature complexes). Sixteen of the dogs with supraventricular arrhythmias also had occasional VPCs. Morphology of the VPCs seen on lead II ECGs was consistent with left bundle branch block in 25 dogs, right bundle branch block in 8, and both in 11.

Conclusions and Clinical Relevance—Results suggest that Boxers with cardiomyopathy and left ventricular dysfunction frequently have arrhythmias of supraventricular or ventricular origin. Whether ventricular dysfunction was preceded by electrical disturbances could not be determined from these data, and the natural history of myocardial disease in Boxers requires further study. (J Am Vet Med Assoc 2005;226:1102–1104)

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in Journal of the American Veterinary Medical Association