TEACHING POINTS
■ Bacterial endocarditis (BE) can occur in abnormal native valves or in surgically corrected or replacement valves and shunts. Fever is the most common symptom, occurring in 80% to 90% of cases. Heart murmur (80%-85%) and chills and diaphoresis (40%-75%) are other common symptoms.
■ The Duke criteria are used to help diagnose BE. The two major criteria are positive blood cultures and/or evidence of endocardial involvement. The six minor criteria include predisposing heart condition or IV drug use, fever, vascular phenomena, immunologic phenomena, microbiological evidence (not meeting major criteria), and echocardiographic findings (not meeting major criteria). Two major, one major and three minor, or five minor criteria suggest a diagnosis of BE.
■ Empiric treatment should be started if sensitivity results are not yet available in patients who are acutely ill. The usual course of antibiotic therapy is 4 to 8 weeks. Blood cultures should be repeated periodically during therapy to document the cessation of bacteremia.
■ Depending on severity, surgery may be necessary to cure BE. Surgical indications for prosthetic valve BE include heart failure, failure of treatment, dehiscence, and evidence of increasing valvular obstruction or worsening regurgitation.
CASE
A 6-year-old girl with a known history of congenital heart disease presented to her pediatrician with a fever and cough. Her most recent cardiac surgery was about 1 year earlier. A chest radiograph demonstrated a right upper lobe pneumonia for which she was prescribed a 10-day course of amoxicillin, which resolved her symptoms. Three days after completing the amoxicillin, however, the patient's symptoms recurred. On her second visit, a repeat chest radiograph demonstrated left lower lobe pneumonia. Blood cultures were obtained, and she was treated with IM ceftriaxone and oral azithromycin. A blood culture was repeated 4 days later. Both blood culture results were positive for coagulase-negative staphylococci. The patient was referred to pediatric cardiology for further evaluation.
History The patient was born with tetrology of Fallot, a type of congenital heart disease, and pulmonary atresia. Tetrology of Fallot manifests with four findings: ventricular septal defect, right ventricular outflow obstruction, right ventricular hypertrophy, and overriding of the aorta. The severity of these findings varies. This patient was born with pulmonary valve atresia, mild right ventricular hypertrophy, and large ventricular septal defect with aortic valve override. While a newborn, she underwent surgical placement of a right ventricle (RV)-to-pulmonary artery (PA) conduit and an 8-mm valveless Gor-Tex tube and patch closure of the ventricular septal defect.
Because of conduit obstruction at 1 year of age, the RV-to-PA connection was revised, and a 12-mm porcine-valved conduit was placed. At age 5 years (10 months prior to her presentation), she had restenosis of the conduit and underwent surgical placement of a 19-mm Carpentier-Edwards pericardial bioprosthetic valve conduit. No obstruction or insufficiency occurred in the immediate postoperative period. Four months after surgery, transthoracic echocardiography (TTE) recorded a peak gradient of 36 mm Hg (normal range: less than 15 mm Hg) across the conduit. Ten months postoperation, the peak gradient increased to about 100 mm Hg. Within the next month, the girl developed a cough and fever.
Physical examination Vital signs were within normal limits. The patient did not appear to be ill or distressed. There was no evidence of splinter hemorrhages, nontender erythematous nodules on the palms or soles (eg, Janeway lesions), or any other rashes. A productive cough was present. Lungs were clear to auscultation except for harsh breath sounds over the left lower lobe. Cardiac examination revealed a normal first and second heart sound without clicks, rubs, or gallops. A harsh grade 4/6 systolic ejection murmur was loudest at the left upper sternal border but was radiating throughout the chest. The remainder of the examination findings were normal.
Diagnostic studies TTE was performed at the time of presentation. The RV-PA-conduit stenosis was not significantly greater than it was on an echocardiogram performed 1 month earlier (peak gradient, 94 versus 100 mm Hg). No evidence of vegetations was present. Transesophageal echocardiography (TEE) was recommended if clinical suspicion existed for bacterial endocarditis (BE), as the patient had limited acoustic windows and TTE may not be able to detect small vegetations.
Blood cultures were redrawn to confirm the earlier positive cultures. Results were again positive for coagulase-negative staphylococci. The organism was resistant to amoxicillin, amoxicillin/clavulanic acid, oxacillin, penicillin, erythromycin, and clindamycin, but it was sensitive to trimethoprim/sulfamethoxazole, vancomycin, and daptomycin. The patient was admitted for further inpatient evaluation and treatment.
Hospital course After admission, the girl was empirically started on vancomycin and ceftriaxone. The infectious disease (ID) department was consulted, and a diagnosis of subacute bacterial endocarditis was made. She was put on antibiotic therapy for 6 weeks. The ceftriaxone was discontinued when the sensitivity became available. TEE demonstrated a 16 × 4-mm vegetation attached on the distal aspect of the medial pulmonary valve leaflet (Figure 1). The vegetation, which moved freely coincident with the valve motion, occupied approximately 50% of the lumen of the pulmonary conduit. The pulmonary stenosis gradient had a peak of 65 mm Hg and a mean of 40 mm Hg.
Cardiovascular surgery was consulted, and based on the finding of obstruction through the conduit, the patient was scheduled for surgery on hospital day 5. During the procedure, the infected/vegetative bioprosthetic valve was extracted (Figure 2), and the right ventricular outflow tract was repaired with a valveless conduit to allow the infection to resolve and eliminate an adherent site for future infections. Tissue culture confirmed the presence of coagulase-negative staphylococci. The pathology of the valve showed acute and chronic inflammation and necrosis with the presence of bacteria colonies.
The patient had an unremarkable recovery. On postoperative day 4, she was discharged with a peripherally inserted central catheter (PICC) line in situ. The PICC permitted administration of IV vancomycin so that she could complete her 6-week prescribed course of antibiotics. The PICC line was replaced once because clots formed. The patient had completed 30 days of IV vancomycin when it was suspected that the PICC line had migrated and was inconsistently patent. The line was then removed and, upon the recommendation of the ID department, she was put on 3 weeks of linezolid therapy. At her most recent visits, she was healthy without any fever or pneumonia. Her blood culture results and inflammatory markers were normal, and gradients through her conduit remained stable.