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There is a group of patients who are at particular risk. In any of these patients, endocarditis should always be high on your concern and I think many of these groups will be familiar to you but there’s one at the end that is new. First, the patients with damaged natural valves and I think all of you are aware that in the past it was mainly congenital heart defects – patients with rheumatic valvular disease. This is less common today. Patients with mitral valve prolapse. Not all of them but ones with certain characteristics, particularly on echocardiogram and when they have persistent murmurs associated with this not uncommon congenital lesion. Asymptomatic septal hypertrophy syndrome and degenerative calcified valves in the elderly patient population all constitute a risk factor as a damaged natural valve endocarditis or heart valve infection.
Intravenous drug users and patients who have prosthetic heart valves. Those who are considered having early prosthetic valves, meaning those less than 60 days of valve replacement can develop endocarditis. But the point is there’s disturbing news here because there are more and more of these patients in our population and a fairly recent article by Fones from the University of Pittsburgh in the annals of 1993 reported on patients with prosthetic heart valves who were followed one year.
This allows us to go into a new group of patients who I think we have to consider very seriously as patients at particular risk. Patients in the hospital setting, there’s a fourth group that we have to be aware of. Not just those with prosthetic valves but those with malignancies. There are increasing reports, most recently from the University of Pittsburgh, about patients with solid organ transplants who develop endocarditis.
They have a disturbingly high mortality – well over 50% in any of the series of those patients that I described. It’s attributed (1) to not recognizing and (2) to the host who is often immunologically impaired and (3) to the nature of the organisms that they get – Staph aureus being particularly important and fungal infections. So I think we also have to be aware that when I say "patients in a hospital setting" we have to enlarge.
One, in the hospital. So bacteremic episodes occurring in patients with prosthetic valves, intravascular devices and this includes AV fistula.
Now, what I’d like to do is talk to you a minute about the diagnosis of the disease. I think you are all aware of the fact that there is news here. Durack and his group at Duke University offered new criteria for assessment in the American Journal of Medicine article that they published in 1994 and since then there have been many, many series reported from other institutions assessing the validity and the usefulness of these new criteria.
As you know, the classic diagnostic criteria that most of us remember, the Von Rheim criteria which Petersdorf published in medicine the journal in 1977 and they were assigned by Von Rheim. Conceptual categories based on our understanding of the pathophysiology of this disease. A documented persistent worse state of bacteremia, an active endocardiopathology and predisposing heart disease with vascular phenomenon that may be embolic or maybe immunologically mediated and that’s kind of how we grew up.
The Duke or the Durack modifications are interesting because they kind of try to model encarditis after rheumatic heart disease which is a disease we still don’t really understand that much about. So there are major criteria and minor criteria and I think at some point we might have to think about this as maybe the flaw in this whole new way of thinking about the disease.
This is the Von Rheim criteria and you’ll notice there are "definite", "probable", "possible" and "rejected" categories and, again, this was to put series together so as to compare experiences with endocarditis so that you’re very kind of sure that the patient has the disease that you’re reporting.
Some of the differences or modifications was that the Durack criteria were finally recognizing IV drug users as a risk factor. As I said, this was published in 1994 and I think we’ve all recognized that. That would be a minor criteria in this and you can change the categories. So that there was definite, not only autopsy or surgical, evidence of infection or a pathology from an embolic event but he loosened it up and allows clinical criteria and that gets to the two major, one major and three minor, five minor criteria and then possible or rejected and eliminates probable. The only point I want to make about this is these new criteria imply that fewer patients will be rejected from the diagnosis and this has implications not only for the series that you would include these patients in but for treatment of these patients. So we may well be treating more patients for endocarditis if we use these criteria than actually have the disease but that may be the safest way.
Also what the Duke criteria do is recognize certain organisms as highly likely to be associated and correlated with having endocarditis and I think this is an extremely useful thing that these modifications offer. (1) That Strep viridans and Strep bovis and the HACEK’s group – Hemophilus, saprophilous, Actinobacillus, Cardiobacterium hominis, Eikenella and Kingella – all mouth organisms – are so highly correlated with endocarditis that when you see just two blood cultures positive for these organisms coming from the community, there really is almost nothing else it could be.