Ever since the days of the second edition of Bouillaud's clinical treatise on diseases of the heart, pneumonia has been recognized as one of the causes of endocarditis. Endocarditis in pneumonia, however, is of infrequent occurrence, as may be inferred from the following statistics:
Thus Aufrecht, in 1,501 cases of pneumonia, observed recent endocarditis only once. Fismer encountered it in 2 of 180 cases; Herman once in 44 cases; Huss 4 times in 2,710 cases; Waller once in 81 cases. It was recognized twice in 498 cases which I analyzed ten years ago, and I have since seen a few other examples. Pye-Smith met with (ulcerative) endocarditis 7 times in 425 cases of pneumonia. Sears and Larrabee found, at autopsy, 9 cases of endocarditis in 341 fatal cases in an analysis of 949 cases of pneumonia. Osler found endocarditis in 16 of 100 fatal cases of pneumonia which he analyzed.
WELLS EF. ENDOCARDITIS AS A COMPLICATION OF PNEUMONIA.. JAMA. 1902;XXXIX(16):978-981. doi:10.1001/jama.1902.52480420030001g