Small Animal Emergency and Critical Care Medicine Q&A 01
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This question was provided by Manson Publishing as part of the OVAL Project. See more Small Animal Emergency and Critical Care Medicine Q&A. |
A ten-year-old, male German Shepherd Dog is evaluated for anorexia and weight loss over 1 week and acute onset profound lethargy/exercise intolerance. The dog is weak, has a temperature of 104°F (40°C) and is tachypneic with mild crackles ventrally and harsh lung sounds dorsally. A systolic and diastolic murmur is auscultated over the left heart base, though the owner reports a murmur had been noted since the dog was 4 months old.
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| What is your tentative diagnosis? | Bacterial endocarditis with secondary acute congestive heart failure or embolic pneumonia. Large breed, male dogs are affected with bacterial endocarditis more commonly. However, it is possible that the murmur is due to congenital aortic stenosis and an infection elsewhere, neoplasia, or because immune-mediated disease is present. |
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| What is the likely source of the murmur? What other valve(s) may be involved? | The origin of the murmur is most likely the aortic valve. Typically, a decrescendo diastolic murmur from aortic insufficiency is present and is usually loudest in early diastole. A systolic murmur may or may not be present; in fact, there may be no murmur at all. The mitral valve in dogs is affected most commonly in bacterial endocarditis, then the aortic valve. |
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| Chest radiographs reveal a diffuse interstitial pattern and only mild cardiomegaly. An echocardiogram is performed (29). What is your diagnosis and how are the radiographic findings consistent with this diagnosis? | When acute mitral regurgitation or aortic insufficiency occurs secondary to bacterial endocarditis, the increased left ventricular volume rapidly increases left ventricular end-diastolic pressure due to limits imposed by the myocardium and pericardial sac; thus, pulmonary edema develops with only mild to moderate compensatory cardiomegaly. The left atrium is usually normal in size at the time of diagnosis. |
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| What diagnostic test(s) would best confirm your suspicion? | Serial blood cultures should be drawn. Positive blood cultures have been obtained in 88% of affected dogs when more than one sample was drawn. |
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| What treatment would you initiate in the acute phase and what is the long-term prognosis? | Diuretics and vasodilators (hydralazine or angiotensin-converting enzyme inhibitor) should be initiated to control the edema, reduce valvular regurgitation and improve forward cardiac output. Myocardial contractility usually remains within normal limits until late in the disease process. A broad-spectrum antibiotic (cephalosporin or penicillin) in combination with an aminoglycoside are started until culture results are available. Corticosteroids are contraindicated. |
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