Surgical pathology of native valve endocarditis in 310 specimens from 287 patients (1985-2004)

Background: Few large studies have documented the clinical and pathologic features of native valve endocarditis (NVE) independently from prosthetic valve endocarditis (PVE). Methods: A retrospective study of medical records of all patients undergoing operation for NVE at Mayo Clinic in Rochester, MN (1985-2004), was performed. Medical records were reviewed from 287 patients for demographics, infecting organism, and comorbidities. Microscopic slides from 310 valves were reviewed for features of infection. Results: The study cohort included 287 patients, with age ranging from 9 to 87 years (mean, 54), yielding 310 valves. Most (73%) were from men, and 84% were regurgitant. Risk factors included bicuspid aortic valve (23%), dental manipulation (20%), mitral valve prolapse (18%), diabetes mellitus (16%), and others (< 5% each); in 15%, no risk factor was identified. The four most commonly identified organisms were viridans group streptococci (28%), Staphylococcus aureus (18%), enterococci (9%), and coagulase-negative staphylococci (8%). NVE was histologically active in 58% and healed in 42%, and affected left-sided valves in 94%. It was associated with embolization in 29%, acute heart failure in 29%, and annular abscess in 18%. Men accounted for a higher percentage of aortic NVE than mitral NVE (82% versus 63%, respectively; P=.001). Among 126 valves with active endocarditis, 25% had no microorganisms identified histologically. Conclusion: NVE affected men nearly three times as frequently as women. Diabetes mellitus emerged as a prevalent (and previously underrecognized) risk factor for NVE. The most common infecting organisms were streptococci and staphylococci. Microorganisms were identified histologically in the majority of active endocarditis cases.