Historical Perspective

Endocarditis, an inflammatory disorder of the endocardium, has been recognized by the anatomical pathologists for some time. Prior to the bacteriological era, however, the various types of endocarditic lesions could not be categorized as infectious or non-infectious. Austin Flint's chapter on endocarditis likely referred to rheumatic valvular heart disease rather than to infectious endocarditis [1]. However, he utilized the terms "acute," "subacute," and "chronic" in his description, and this classification was subsequently adopted as standard nomenclature.

The diagnosis of IE remained challenging and continued to be dependent on a constellation of infectious symptoms and signs in association with bacteremia, auscultatory evidence of valvular involvement, and signs of large-and/or small-vessel peripheral arterial embolization. This dependence on both clinical skills and the bacteriological laboratory was, in the latter part of the 20th century, supplemented by the addition of echocardiography visualization of the lesion and of the assessment of its hemodynamic and structural consequences.

In 1945, R. H. Major, in a comprehensive review, The History of Endocarditis, mentions Laennec's attribution of the first mention of this disorder to Lazare Riviere in 1707: "In the left ventricle of the heart round caruncles were found like the substance of the lungs, the larger of which resembled a cluster of hazelnuts and filled up the opening of the aorta" [2]. Major notes that Morgagni, in 1761, while observing a ruptured aortic valve cusp observes that "from the very lips of their rupture other excrescences were protuberant." Virchow, the great anatomical pathologist, noted in 1856 that IE was associated with emboli and that he had seen "innumerable vibrions" in a thrombus

[2]. Klebs, in 1875, had become convinced that all cases of IE were infectious in origin [2]. In 1878, Rosenbach demonstrated in experimental studies that IE was associated with bacteremia and damaged cardiac valves and he recommended that the diagnosis be dependent on the presence of positive blood cultures in association with specific signs and symptoms [2].

It is instructive to view the understanding of infectious IE through the eyes of a single individual, Sir William Osler, as revealed in successive editions of his textbook The Principles and Practice of Medicine. The first edition, in 1892, divides endocarditis into "acute" and "chronic" forms. Acute endocarditis was further divided into contained "simple" and "malignant" forms

[3]. In simple endocarditis there were small vegetations with microorganisms in association with systemic symptoms, fever, and a heart murmur [3]. In malignant endocarditis, there was acute IE with "a malignant character" [3]. Symptoms were varied and diverse and might include fever, sweats, weakness, delirium, and emboli. Malignant endocarditis was subdivided into a Septic type, a typhoid type, and a "cardiac group, the latter being associated with chronic valvular heart disease, fever, and "evidence of recent IE" [3]. Osler noted that the diagnosis of IE was often "difficult" but was easy when there were "marked embolic symptoms." To the modern reader, although his classification may be difficult to interpret, his conclusion about the difficulty in diagnosing the disorder continues to be appreciated.

In his 1909 article, "Chronic Infectious Endocarditis:", Osler reported ten cases he had accumulated between 1888 and 1908—all of whom had died [4]. He noted that "endocarditis with fever as its only symptom may be prolonged for weeks or months" and mentioned that some patients had had fever for 4-12 months. He clearly understood the infectious nature of the disease and commented that "it has long been recognized that malignant endocarditis is really an acute septicemia with localization in the endocardium." He then noted that, "as a rule the valves involved are already the seat of a sclerotic change" and that "the source of infection is only rarely to be determined." [4]

The diagnosis of IE in these ten cases was dependent on the presence of fever or chills, purpura, or "painful nodular erythema" (subsequently given the eponym of Osler's nodes—see Figure 6.1), mitral or aortic murmurs, and embolism (the latter appearing in four of the ten cases). Osler noted that the most suggestive features of IE were (a) a previous valve lesion, (b) embolic features, (c) skin lesions (see Figures 6.2 and 6.3), and (d) progressive cardiac changes. As a final note he added, "with...blood cultures one should now be able to determine the presence of septicemia" [4].

In Osler's 8th edition of his textbook, the disorder became classified as acute or chronic IE with the usual culprits being streptococci, staphylococci, pneumococci, and gonococci [5]. In this 1912 edition he highlighted the difficulty of diagnosing infectious IE and remarked that it "rests upon physical signs which are notoriously uncertain." In the 10th edition in 1926 he divided IE into acute, subacute, and chronic forms and emphasized that "blood cultures aid greatly and are necessary for an etiological diagnosis" [6]. By the 14th edition in 1942 he had identified "acute non-bacterial endocarditis," in addition to "acute," "subacute," and "chronic bacterial endocarditis" [7]. The diagnosis of bacterial IE was still dependent on a constellation of signs and symptoms: fever, sweats, weight loss, large- and small-vessel emboli, clubbing, leukocytosis, heart murmurs, splenomegaly, hematuria, and positive blood cultures.

Figure 6.1. Osle!s node—Violaceous, tender nodules on the volar surfaces of the fingers (associated with minute infective emboli or immune complex deposition). (Color Atlas & Synopsis of Clinical Dermatology, Fitzpatrick, TB, et al. McGraw-Hill, © 2001, with permission of the McGraw-Hill Companies).

Figure 6.1. Osle!s node—Violaceous, tender nodules on the volar surfaces of the fingers (associated with minute infective emboli or immune complex deposition). (Color Atlas & Synopsis of Clinical Dermatology, Fitzpatrick, TB, et al. McGraw-Hill, © 2001, with permission of the McGraw-Hill Companies).

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