Case Presentation:
A 42‐year old man who uses intravenous heroin daily presented with sudden onset, excruciating and left‐sided pleuritic chest pain along with shortness of breath. He had a fever of 104 degrees Fahrenheit and a pulse oximetry reading of 84% on room air. He had clear lung fields, absence of cardiac murmurs and a tender and warm right hand with limited range of motion. Leukocytosis with bandemia was present. A portable chest X‐ray showed bilateral hazy infiltrates. Computed tomography of the chest revealed multiple cavitary pulmonary nodules with right hilar lymphadenopathy. Several serial blood cultures grew out methicillin‐resistant staphylococcus aureus while a transthoracic echocardiogram (TTE) showed a normal left ventricular ejection fraction without any gross valvular abnormalities. A trans‐esophageal echocardiogram (TEE) also showed no vegetation on any of the cardiac valves.
In spite of the absence of echocardiographic evidence of endocardial involvement, this patient met the Duke Criteria for endocarditis and was treated with a prolonged course of antibiotics.
Discussion:
With an estimated annual incidence of 3 to 9 cases per 100,000 persons in industrialized countries, an internist working in an urban environment may encounter infective endocarditis. In clinical practice, the diagnosis is frequently made by employment of the Duke Criteria that involves 2 major criteria: definite echocardiographic evidence of endocarditis and positive blood cultures with bacteria that typically cause infective endocarditis. There are also six minor criteria: predisposing cardiac condition or intravenous drug use; fever; vascular phenomena; immunologic phenomena; echocardiographic findings suggestive of infective endocarditis without meeting major criteria; and ambiguous blood cultures. A diagnosis of infective endocarditis is made if the patient has: two major criteria, one major criterion plus three minor, or 5 minor criteria.
Endocarditis in intravenous drug users presents somewhat distinctively. Almost 50% of these endocarditis cases involve the tricuspid valve and present with fever and faint or no murmur. These patients often lack the systemic vascular stigmata of endocarditis and may present with pulmonary septic emboli.
The value of echocardiography is emphasized in the Duke Criteria. TTE is specific, yet has less sensitivity detecting vegetations in only 65% of patients with definite endocarditis. In patients with a high pre‐test probability for endocarditis, a TEE can detect vegetations in up to 90% of patients with endocarditis; yet can yield false‐negatives in up to 18% of patients. A repeat TEE is generally recommended in these cases.
In spite of the absence of echocardiographic evidence of endocarditis, we used the Duke Criteria to make the diagnosis due to the presence of MRSA bacteremia (one major criterion) along with fever, history of intravenous drug use, and radiographic evidence of septic emboli (three minor criteria). It is important to recognize the limitations of diagnostic tests and always appreciate more global assessments of the clinical picture, represented in this case by the Duke Criteria.
Conclusions:
Diagnosis of endocarditis can be done by the Duke Criteria without extensive cardiac imaging. Application of these criteria may lead internists to timely diagnosis.