The prevalence of infective endocarditis after aortic valve replacement.

Replacement valve endocarditis occurred in 3.7% of 2443 patients who underwent primary or redo aortic valve replacements at The Prince Charles Hospital between December 31, 1969 and January 1, 1992, based on a cross-sectional follow-up in 1992 which was 98.8% complete. Because some patients had re-replacements during the study period, a total of 2686 operations were considered for analysis. A variety of replacement devices were used, including 571 allografts (21%), 1152 xenografts (43%), and 880 mechanical valves (36%). Insertion of an allograft valve resulted in a constant risk of endocarditis which, by multivariable hazard function analysis, negated the effect of any early-phase factors (p < 0.0001). With other replacement devices, the risk of infection peaked early after operation (9 weeks) and then gave way to a constant risk. Compared with the risk associated with allograft valves, constant risk was higher when the replacement device was a Carpentier-Edwards xenograft (n = 1021, p = 0.02) and lower when a St. Jude Medical mechanical valve was used (n = 505, p = 0.05). In nonallograft recipients, the presence of active preoperative endocarditis (p < 0.0001) or a concomitant synthetic synthetic aortic root replacement (p = 0.0006) increased the magnitude of the early peaking risk. Regardless of replacement device, constant risk was increased in patients with renal dysfunction (p = 0.01), in younger patients 0.04). When preoperative endocarditis was caused by Staphylococcus aureus, culture-positive postoperative wound infection was associated with increased risk of replacement valve infection (p < 0.001) and when it occurred, the same organism was usually responsible (86%). Identification of patients at increased risk for replacement valve infection may lead to reduced morbidity through strategies such as selective use of replacement devices and antimicrobial prophylaxis.