Remember that Lack of Positive Blood Cultures does not Rule Out Bacterial Endocarditis
Harjot K. Singh MD
Aruna K. Subramanian MD
Infective endocarditis (IE) is generally defined by vegetative cardiac lesions in the setting of positive blood cultures. However, the lack of a single diagnostic test has led to several diagnostic algorithms, of which the Duke criteria are the most widely accepted. The Duke criteria have been shown to have a specificity of 99% and a negative predictive value of 92%. Despite the diagnostic difficulty, when infective endocarditis is suspected, empiric therapy is warranted because of its high morbidity and mortality.
Signs and Symptoms
The signs and symptoms of infective endocarditis can vary greatly and have a low sensitivity and specificity for infective endocarditis. Fevers, chills, and sweats are common. Fatigue, syncope, congestive heart failure, and embolic events can occur. On exam, patients can have fever, new or louder pre-existent murmurs, splinter hemorrhages, Janeway lesions, Osler nodes, or Roth spots. Risk factors endocarditis include presence of prosthetic valves, structural heart disease, intravenous drug use, and indwelling catheters.
Definitive diagnosis using the Duke criteria requires fulfillment of two major criteria, one major and three minor, or five minor criteria.
Major Criteria
Two separate positive blood cultures for a typical organism (community-acquired Staphylococcus aureus or enterococci without another infectious focus, Streptococcus viridans, Streptococcus bovis, or HACEK1 group), or persistently positive blood cultures with any organism (e.g., two specimens drawn 12 hours apart, all of three separate cultures at least 1 hour apart, or most of ≥ four cultures)Related posts:
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