History
A 10-year-old 28.0-kg (61.6-lb) spayed female Golden Retriever was evaluated because of a 2-day history of lethargy and anorexia. The dog also had a history of hypothyroidism and idiopathic epilepsy, for which it was receiving levothyroxine and phenobarbital, respectively. In addition, approximately 2 weeks before the examination, forelimb lameness had developed and resolved spontaneously.
On examination, the dog was lethargic and tachypneic (60 breaths/min; reference range, 16 to 40 breaths/min) and had a rectal temperature of 39.4°C (102.9°F). Cardiac auscultation revealed an irregular heart rhythm with a heart rate of 80 beats/min (reference range, 60 to 140 beats/min) and a grade 2/6 left apical systolic murmur. Occasional femoral pulse deficits were noted. Results of a CBC and serum biochemical analyses revealed mild anemia (Hct, 35%; reference range, 37% to 57%), lymphopenia (650 lymphocytes/μL; reference range, 760 to 4,230 lymphocytes/μL), thrombocytopenia (46,000 platelets/μL; reference range, 200,000 to 500,000 platelets/μL), hypoalbuminemia (albumin concentration, 2.7 g/dL; reference range, 2.9 to 4.0 g/dL), hyperglobulinemia (globulin concentration, 4.4 g/dL; reference range, 2.2 to 3.6 g/dL), and high alkaline phosphatase activity (146 U/L; reference range, 5 to 129 U/L). Results for prothrombin and partial thromboplastin time were unremarkable. The dog had a markedly high plasma cardiac troponin I concentration (41.47 ng/mL; reference range, < 0.50 ng/mL). A screening testa to detect Dirofilaria immitis antigen and antibodies against Anaplasma phagocytophilum, Borrelia burgdorferi, and Ehrlichia canis yielded a faintly positive result for E canis. Electrocardiography revealed an accelerated idioventricular rhythm, and echocardiography was performed (Figure 1; Supplementary Video S1, available at avmajournals.avma.org/doi/suppl/10.2460/javma.254.10.1155).
Transthoracic right parasternal long-axis 2-D echocardiographic image of a 10-year-old 28.0-kg (61.6-lb) spayed female Golden Retriever evaluated because of a 2-day history of lethargy and anorexia.
Citation: Journal of the American Veterinary Medical Association 254, 10; 10.2460/javma.254.10.1155
Transthoracic right parasternal long-axis 2-D echocardiographic image of a 10-year-old 28.0-kg (61.6-lb) spayed female Golden Retriever evaluated because of a 2-day history of lethargy and anorexia.
Citation: Journal of the American Veterinary Medical Association 254, 10; 10.2460/javma.254.10.1155
Transthoracic right parasternal long-axis 2-D echocardiographic image of a 10-year-old 28.0-kg (61.6-lb) spayed female Golden Retriever evaluated because of a 2-day history of lethargy and anorexia.
Citation: Journal of the American Veterinary Medical Association 254, 10; 10.2460/javma.254.10.1155
Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →
Diagnostic Imaging Findings and Interpretation
Echocardiography revealed a large independently oscillating vegetative mass on the dog's mitral valve (Figure 2; Supplementary Video S1). The mass measured approximately 1.8 × 0.9 cm, appeared pedunculated, and was attached to the anterior mitral valve leaflet and supporting chordae tendineae, a portion of which was suspected to have ruptured. The left ventricle was small in systole and diastole and had dyskinetic motion. The left atrium was mildly enlarged. Color flow Doppler echocardiography revealed mitral regurgitation with a mean regurgitant jet area-to-left atrial area ratio of approximately 37%,1 mild tricuspid regurgitation with no evidence of pulmonary hypertension, and trivial aortic and pulmonic insufficiency. Given the dog's clinical signs and the echocardiographic findings, the primary differential diagnosis was bacterial endocarditis of the mitral valve.
Same echocardiographic image as Figure 1. A large, multilobulated, heterogenous mass (arrow) extends from the mitral valve and into the left atrium, consistent with a vegetative lesion indicative of bacterial endocarditis. The ECG shows a sinus complex followed by multiple fusion complexes, consistent with accelerated idioventricular rhythm. LA = Left atrium. LV = Left ventricle. RA = Right atrium. RV = Right ventricle.
Citation: Journal of the American Veterinary Medical Association 254, 10; 10.2460/javma.254.10.1155
Same echocardiographic image as Figure 1. A large, multilobulated, heterogenous mass (arrow) extends from the mitral valve and into the left atrium, consistent with a vegetative lesion indicative of bacterial endocarditis. The ECG shows a sinus complex followed by multiple fusion complexes, consistent with accelerated idioventricular rhythm. LA = Left atrium. LV = Left ventricle. RA = Right atrium. RV = Right ventricle.
Citation: Journal of the American Veterinary Medical Association 254, 10; 10.2460/javma.254.10.1155
Same echocardiographic image as Figure 1. A large, multilobulated, heterogenous mass (arrow) extends from the mitral valve and into the left atrium, consistent with a vegetative lesion indicative of bacterial endocarditis. The ECG shows a sinus complex followed by multiple fusion complexes, consistent with accelerated idioventricular rhythm. LA = Left atrium. LV = Left ventricle. RA = Right atrium. RV = Right ventricle.
Citation: Journal of the American Veterinary Medical Association 254, 10; 10.2460/javma.254.10.1155
Treatment and Outcome
Bacterial cultures were performed on samples of urine and blood, and the dog was treated with amikacin (17.9 mg/kg [8.1 mg/lb], IV or SC, q 24 h), ampicillin-sulbactam (53.6 mg/kg [24.4 mg/lb], IV, q 12 h), and doxycycline (4.5 mg/kg [2.0 mg/lb], PO, q 12 h). Marked clinical improvement, characterized by signs of improved energy levels and appetite, was noted within 24 hours after the medication was initiated. Results of bacterial culture of urine were negative; however, all 3 bacterial cultures of serial blood samples were positive for Corynebacterium spp. On the basis of results from susceptibility testing, amikacin and ampicillin-sulbactam were discontinued after 1 week of treatment and doxycycline was continued for 2 weeks. At a recheck examination 2 weeks later, the dog's reported activity level had improved to approximately 90% of normal. Echocardiography revealed substantial reduction in the size of the vegetative lesion, progressive but mild left atrial enlargement, persistent mitral valve regurgitation, and the presence of a flail leaflet (Figure 3; Supplementary Video S2, available at avmajournals.avma.org/doi/suppl/10.2460/javma.254.10.1155). Plasma cardiac troponin I concentration was 0.09 ng/mL, improved from when initially measured. The dog was prescribed amoxicillin (20 mg/kg [9.1 mg/lb], PO, q 12 h for 6 weeks) with recommendations for recheck bacterial cultures of blood in 1 week, then again 2 weeks after completing antimicrobial treatment. The owner did not heed the recommendation but returned the dog for a recheck examination approximately 14 weeks after the initial examination (approx 6 weeks after completing the antimicrobial treatment). At that time, the dog was reported as doing well at home, and recheck echocardiography revealed resolution of the vegetative lesion, unchanged left heart size, but persistence of mitral valve regurgitation. Blood cultures yielded no growth. The dog did not have recurrence of bacterial endocarditis or associated clinical signs before it died from an unrelated cause 4 years later.
Transthoracic right parasternal long-axis 2-D echocardiographic image of the dog in Figure 1 obtained during a recheck examination 2 weeks later. The vegetative lesion is substantially smaller than it was 2 weeks earlier. The mitral valve has clinically relevant prolapse, and a portion of it appears to point back (arrowhead) into the left atrium, indicative of a probable flail leaflet; however, persistence of the vegetative lesion may also contribute to the appearance of the leaflet. The ECG shows a normal sinus rhythm with a single ventricular premature complex at the beginning of the frame. See Figure 2 for key.
Citation: Journal of the American Veterinary Medical Association 254, 10; 10.2460/javma.254.10.1155
Transthoracic right parasternal long-axis 2-D echocardiographic image of the dog in Figure 1 obtained during a recheck examination 2 weeks later. The vegetative lesion is substantially smaller than it was 2 weeks earlier. The mitral valve has clinically relevant prolapse, and a portion of it appears to point back (arrowhead) into the left atrium, indicative of a probable flail leaflet; however, persistence of the vegetative lesion may also contribute to the appearance of the leaflet. The ECG shows a normal sinus rhythm with a single ventricular premature complex at the beginning of the frame. See Figure 2 for key.
Citation: Journal of the American Veterinary Medical Association 254, 10; 10.2460/javma.254.10.1155
Transthoracic right parasternal long-axis 2-D echocardiographic image of the dog in Figure 1 obtained during a recheck examination 2 weeks later. The vegetative lesion is substantially smaller than it was 2 weeks earlier. The mitral valve has clinically relevant prolapse, and a portion of it appears to point back (arrowhead) into the left atrium, indicative of a probable flail leaflet; however, persistence of the vegetative lesion may also contribute to the appearance of the leaflet. The ECG shows a normal sinus rhythm with a single ventricular premature complex at the beginning of the frame. See Figure 2 for key.
Citation: Journal of the American Veterinary Medical Association 254, 10; 10.2460/javma.254.10.1155
Comments
Bacterial endocarditis is an uncommon but often fatal disease that is a consequence of bacteremia and endothelial damage to the heart valves.2 On the basis of criteria3 used to help diagnose bacterial endocarditis in humans, combinations of major and minor criteria are used to diagnose bacterial endocarditis in veterinary patients.4,5 Major criteria involve identification of a vegetative valvular lesion or documentation (ie, bacterial culture results) of bacteremia. Minor criteria generally reflect the underlying infectious or inflammatory process (eg, rectal temperature > 32.2°C [102.5°F], anti-Bartonella antibody titer > 1:1,024, thromboembolic disease, or immune-mediated disorders [eg, polyarthritis or glomerulonephritis]), predisposing risk factors (eg, the presence of subaortic stenosis), or overrepresented characteristics (eg, medium or large dog breeds). Definitive diagnosis of bacterial endocarditis is obtained by identifying the presence of 2 major criteria, or 1 major criteria in combination with 2 minor criteria. The presence of only 1 major and 1 minor criteria or 3 minor criteria is suggestive of, but not definitive for, a diagnosis of bacterial endocarditis.
Echocardiography remains the diagnostic imaging modality of choice for accurate diagnosis of bacterial endocarditis, and the finding of an oscillating, hyperechoic, irregularly shaped mass attached to the flow side of a cardiac valve is considered pathognomonic for a vegetative lesion. A recent meta-analysis6 shows that the overall sensitivity and specificity of transthoracic echocardiography in detecting bacterial endocarditis in people are 71% and 80%, respectively. In addition, echocardiography is useful in detecting complications, determining prognosis, and assessing hemodynamic consequences of bacterial endocarditis. Complications can include functional impairment of cardiac valves, leading to valvular regurgitation or stenosis; valve leaflet perforations; chordae tendineae ruptures; abscess and fistula formation; myocardial infarction; and systemic embolization. In humans, the risk of embolization is higher with vegetative lesions that are > 10 mm in diameter and with vegetative lesions that have a greater degree of mobility.7 In addition, serial echocardiography to monitor vegetative lesion size can be helpful in evaluating response to treatment. Given the rapid resolution of the vegetative lesion in the dog of the present report, it was possible that the vegetative lesion embolized to the systemic circulation; however, the dog did not have clinical signs consistent with systemic embolization during that time. The dog's reported lameness 2 weeks before examination, however, may have been secondary to an embolism. Further, echocardiography has prognostic value because vegetative lesions of the aortic valve are associated with a grave prognosis in dogs (median survival time from diagnosis, 3 days), whereas dogs with vegetative lesions on the mitral valve live substantially longer (median survival time from diagnosis, 476 days).8
The clinicopathologic, microbiological, and echocardiographic findings for the dog in the present report were typical for bacterial endocarditis, and Corynebacterium bacterial endocarditis has been reported in dogs.9,10 In 1 dog, a cyst near the sacrum was suspected to have been the reservoir of the Corynebacterium sp involved,9 whereas another dog had a ventricular septal defect and developed mural endocarditis along the right ventricular outflow tract.10 However, unlike those 2 dogs, no known inciting event or predisposing factor could be identified for the dog of the present report; nonetheless, echocardiography was instrumental in rapidly diagnosing and guiding treatment for bacterial endocarditis in this dog.
Footnotes
SNAP 4Dx, Idexx Laboratories Inc, Westbrook, Me.
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