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

Few large studies have documented the clinical and pathologic features of native valve endocarditis (NVE) independently from prosthetic valve endocarditis (PVE).

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.

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.

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.