Background: Cardiac valves excised from patients with either confirmed or suspected infective endocarditis (IE) are routinely sent for histopathological analysis. However, there are only a few studies describing the histopathological findings in such valves in a large series of patients. The purpose of this study was to examine and describe these findings.
Methods: Episodes of IE that were operated on between July 1, 2007 and July 1, 2014 were selected for this study. IE was defined as meeting Duke Criteria for definite IE. Surgical pathology reports for the identified patients were analyzed for the presence of 8 different histological markers: polymorphonuclear leukocytes (PMNs), lymphocytes, histiocytes, foamy histiocytes, neovascularization, giant cells, fibrin deposits, and microorganisms on special staining. A heatmap of histological markers was done.
Results: Of 862 valves sent for histopathological examination, 41 were excluded because only gross examination was done. The remaining 821 valves came from 703 episodes of IE in 679 patients. The majority (59%) were native valves. Bovine pericardial valves were the most common prosthetic valves (46% of prosthetic valves). Microorganisms, fibrin deposits, and PMNs, were seen in 67%, 61%, and 56% of valves, respectively. There was stepwise clustering of histological markers along the sequence: microorganisms / fibrin deposits, PMNs, neovascularization, lymphocytes, histiocytes / foamy histiocytes, giant cells, and fibrosis (figure), but no clustering by valve type, valve position, microorganism or the reading pathologist. 56% had acute inflammation (presence of PMNs), 62% had chronic inflammation (neovascularization, lymphocytes, histiocytes, foamy histiocytes, or giant cells), and 92% had acute / chronic inflammation or microorganisms. Microorganisms were seen in 53%, 48%, and 32%, respectively, on Gram, Gomori methenamine silver, and periodic acid Schiff staining.
Conclusion: Histological markers of inflammation (acute and/or chronic) or microorganisms can be detected in the majority of patients (92%) with infective endocarditis. All valves removed at surgery in patients with IE should be examined histologically to verify the diagnosis, and absence of findings of IE should cast doubt on the diagnosis.