Case 2 A 31-year-old warehouse manager with progressive dyspnea was transferred from an outside hospital. His illness began 8 months earlier with a dry cough and progressive fatigue. His past history was negative except for an asymptomatic heart murmur. On examination, he was pale and diaphoretic with a temperature of 36°C, pulse 110, and blood pressure of 108/56mm Hg. Neck veins were distended beats/min; loud heart murmurs and diffuse airway crackles were heard. The spleen was palpable. Blood cultures were drawn and antibiotics started.
As the patient was being wheeled for urgent heart surgery, he suffered a huge left-sided stroke. Contrast studies showed a leaking basilar artery aneurysm with subarachnoid hemorrhage. Once his neurologic problem stabilized, urgent mitral and aortic valve replacement was performed. Both valves were severely damaged and rife with vegetations. Admission blood cultures grew viridans streptococci, susceptible to penicillin. After prolonged hospitalization, the patient was transferred for continued care to a rehabilitation unit closer to home.
Comment: Neurologic complications of endocarditis are more common than generally appreciated, and occur in at least one third of patients at the time of diagnosis. Stroke is the most frequent finding, but encephalopathy, retinal embolic lesions, mycotic aneurysm, brain abscess, and meningitis can also occur. Fortunately, most neurologic problems resolve with medical management, but as seen in this patient, some are devastating and have permanent sequelae.
Organisms responsible for the majority of cases of native valve endocarditis are streptococci, as was true in Osler’s time. Staphylococcus aureus is next in frequency, followed by gram-negative bacilli, fungi, coagulase-negative staphylococci, and a poorly-defined category of “culture negative” cases. Therapy for infection caused by penicillin-susceptible streptococci is straightforward. The preferred agent is intravenous penicillin or ampicillin, with ceftraxione or vancomycin as alternatives. Streptococci less susceptible to penicillin, including nutritionally variant organisms, are treated more vigorously with a penicillin and low-dose aminoglycoside.
The HACEK group of gram-negative bacteria (Haemophilus, Actinobacillus, Cardiobacterium, Eikenella, and Kingella species) often produce large vegetations. Embolic lesions to major organs or extremities are a fairly common presenting feature. Treatment with ceftriaxone or ampicillin plus gentamicin is usually successful.
“Culture negative” endocarditis includes infections due to microorganisms difficult to culture on standard media. These uncommon pathogens include Bartonella, Brucella, Chlamydia, Coxiella, Francisella, Legionella, and Tropheryma whippeli.
Bartonella endocarditis has been reported in the homeless population. Blood cultures are usually negative. Serology is helpful. More recently, polymerase drain reactions (PCR) from resected valve tissue have proven useful. Treatment of choice is ampicillin plus gentamicin, but mortality remains approximately 25%.
Patients with endocarditis due to Coxiella burnetii (Q fever) are likewise difficult to diagnose. They may not have fever. However, there is generally underlying valvular heart disease, and frequently patients are immunosuppressed. Vegetations are rarely detected on echocardiogram. Routine blood cultures are negative. Fortunately, serology is quite specific for the diagnosis. A combination of doxycycline and chloroquine is the current treatment of choice.
PCR and special immunohistochemical techniques may be useful in the diagnosis of these unusual etiologies. Unfortunately, the methodology is not currently available at most hospitals. Broad-range PCR on surgical tissue help to identify more typical organisms (staphylococci and streptococci), whose growth may be suppressed by conventional antibiotic therapy. Although promising, PCR technology may lack specificity in these cases.
Case 3 A 61-year-old executive was admitted with a 4 week history of fevers and fatigue. Three months earlier he had undergone a bovine aortic valve replacement with mitral valve repair. Blood cultures drawn by a local physician grew methicillin-resistant Staphylococcus epidermidis (MRSE). Despite antibiotics, the patient’s fatigue persisted and he returned for further evaluation. On examination, he was afebrile, with a resting pulse of 71 beats/min and a blood pressure of 135/63mm Hg. However, he was very pale. Loud systolic and diastolic murmurs were heard throughout the precordium. His spleen was enlarged and very soft.