Prosthetic valve endocarditis: clinicopathologic analysis of 22 necropsy patients with comparison observations in 74 necropsy patients with active infective endocarditis involving natural left-sided cardiac valves.

Clinical and morphologic features are described in 22 necropsy patients with endocarditis involving rigid-framed prosthetic valves: aortic in 15 patients and mitral in 7. The interval from valve replacement to onset of symptoms of prosthetic valve endocarditis was less than 2 months in 8 patients and longer than 2 months in 14 patients. The most frequent infecting organism was the Staphylococcus (13 patients). In each of the 22 patients the infection was located behind the site of attachment of the prosthesis to the valve ring, and the infection spread to adjacent structures in 13 patients, 11 of whom had aortic prostheses. Prosthetic detachment causing severe regurgitation occurred in 12 of the 15 patients with an infected aortic valve prosthesis, and in 2 of the 7 with an infected mitral valve prosthesis. Prosthetic obstruction by vegetative material occurred in 5 of 7 patients with prosthetic mitral infection and in only 1 of 15 with prosthetic aortic infection. High degrees of conduction defects developed in seven patients with aortic prosthetic valve endocarditis: complete heart block in five, and complete left bundle branch block in two. Comparison of observations in the 22 patients with prosthetic valve endocarditis with those in 74 patients with active infective endocarditis involving natural left-sided cardiac valves revealed significant (P less than 0.05) differences in the percent with ring abscess, hemodynamic consequences of the endocarditis (valve stenosis), frequency of Staphylococcus as the causative organism and percent with complete heart block or left bundle branch block. No significant differences were observed between the two groups when comparing age, sex, type of underlying valve disease or frequency of organ infarcts of splenomegaly.