Infective endocarditis: a frequent disease in dialysis patients.

Abstract

The epidemiological profile of infective endocarditis (IE) has changed dramatically over the last few years [1]. Once a disease affecting young adults with previously well identified valve disease (mostly rheumatic disease), IE is now affecting older patients, a significant proportion of whom have no previously known valve disease and develop IE as the result of health-care associated procedures [2]. Actually, if IE was commonly classified in four categories, namely native valve IE, prosthetic valve IE, IE in i.v. drug users (IVDUs), and nosocomial IE, health-care associated IE should probably be added as a fifth category in the near future because of its increasing incidence. Within this new category, IE in chronic haemodialysis (HD) patients appears to be the most important subgroup [3,4]. Incidence and risk factors The most convincing demonstration that HD patients are increasingly developing IE was provided recently by Cabell et al. [4] who performed trend analyses in the IE database of the Duke University Medical Center in the 1993–1999 period. Not only did they show that the overall proportion of HD patients in their sample of 329 IE patients was as high as 20%, but also that the proportion of HD patients increased from 6.7 to >20% over the 7 year study period. This was associated with a significant increase of Staphylococcus aureus IE from 10 to 68% (P-value for trend <0.001). Finally, HD was the best predictor of S.aureus as the causative agent of IE. In a recent 1 year cross-sectional survey of IE in France [2], 13 of 390 patients were receiving chronic HD treatment. Based on these figures and on the number of HD patients in France (25 000–30 000), the incidence of IE in HD patients was 1.7–2.0 cases/ 1000 patients, which is 50–60 times higher than the overall incidence of IE in France. Using the United States Renal Data System, Abbott et al. [3] also demonstrated that HD patients are at increased risk for IE compared with the general population. The incidence of IE in 1996 was 483 per 100 000 personyears in HD patients, while it was 6.5 per 100 000 person-years in the general US population. This difference accounted for an age-adjusted incidence ratio of IE in the HD population of 17.9 (95% CI 6.6–48.9) compared with the general population. Three recent retrospective studies reporting all cases of IE diagnosed in HD patients from five dialysis centres concurred with the same two findings: (1) S.aureus is the predominant causative pathogen, being responsible for 40–80% of the cases; and (2) IE in HD patients has a poor prognosis, as illustrated by in-hospital and 1 year death rates ranging from 25 to 45% and 46 to 75%, respectively [5–7]. Another way to assess the risk of IE in HD patients is to evaluate the outcome of bacteraemia in this population. Marr et al. [8] prospectively followed up 445 HD patients for 18 months. Sixty-two patients developed 65 episodes of S.aureus bacteraemia, 15% of which were complicated with IE. Interestingly, this study showed that 53% of the patients with S.aureus bacteraemia had a dual-lumen tunnelled, cuffed catheter as a vascular access device. More recently, of 210 prospectively evaluated HD patients who developed S.aureus bacteraemia between 1994 and 2001, 36 patients (17.1%) developed an endocarditis [9]. Once again in this series, more than 55% of the patients were dialysed via tunnelled catheters. In another large prospective study of nearly 1000 HD patients, catheters, especially long-term implanted catheters, were found to be the most important risk factor of bacteraemia in HD patients, with a relative risk of 7.6 (95% CI 3.7–15.7) compared with arteriovenous fistula [10]. There are several potential explanations for the increased incidence of IE in HD patients. Ageing of dialysis population may act through the increased