Prosthetic endocarditis after TAVI, rare and difficult to diagnose

Original title: Prosthetic valve endocarditis after transcatheter aortic valve implantation: the incidence in a single-centre cohort and reflections on clinical, echocardiographic and prognostic features. Reference: Miriam Puls et al. EuroIntervention 2013;8:1407-1418.

Prosthetic valve endocarditis is a serious complication of surgical valve replacement and occurs in 0.3 to 1.2% of patients per year. It is basically divided in early prosthetic endocarditis, (within one year of surgery), and late, (past year), the subdivision is due to significant differences in the micro-organisms that produce it. The disease has a high inhospital mortality up to 38% for early endocarditis and 25% for the latter. According to the little information that exists in the literature, endocarditis after percutaneous aortic valve replacement (TAVI) seems very uncommon. The present study describes the experience of a center and discusses the special characteristics of this pathology post TAVI. 

Between 2008 and 2010 there were 180 procedures of percutaneous aortic valve replacement, which represents the initial experience of the center. During a mean follow up of 319 days, 5 cases of endocarditis after TAVI were observed. After performing the analysis of Kaplan-Meier curves these 5 patients represent a 3.4% incidence of endocarditis for this cohort or an incidence of 2.9% per patient per year. Endocarditis was mostly early, (4 out of 5), with typical endocarditis germs, (Staphylococcus aureus, Enterococcus faecalis and Streptococcus gordonii), except in one patient who was rescued from Escherichia coli. There were no significant differences in procedure time, contrast volume, valve type or access used between the patients with endocarditis and those who had not.

Conclusion: 

Prosthetic valve endocarditis after TAVI is particularly difficult to diagnose, making this type of patient especially vulnerable. There is little experience in the interpretation of trans-esophageal echocardiogram images that have different characteristics than those of conventional prosthetic valves.

Commentary: 

The delay in diagnosis can be a major cause of morbidity in these patients. This delay may be due to the frequent atypical presentation in this age group and the inability to accurately interpret trans-esophageal echocardiograms. These difficulties are given because 3 of the 4 criteria for endocarditis in the echocardiogram are difficult or impossible to apply in the context of TAVI, (suture dehiscence, valvular insufficiency, abscess). Only large vegetations leave no doubt but these appear late in the course of the disease, (small ones cannot be generated by the prosthetic device). A patient with positive cultures and consistent symptoms, in the absence of another focus and even when showing unconvincing echocardiographic images, should probably receive antibiotic treatment if one suspects this complication. 

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