Investigating whether bacteria or other organisms are present in the bloodstream at the time of transcatheter aortic valve implantation (TAVI)

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Aortic stenosis is a common valvular abnormality in adults. Its incidence increases with age. The only effective treatment options for severe aortic stenosis are surgical aortic valve replacement (SAVR) or transcatheter aortic valve implantation (TAVI). TAVI represents a less invasive alternative to SAVR. In patients with high surgical risk TAVI has been associated with increased 1-year survival compared with SAVR, along with reduced risk of death and hospitalisation compared with conservative management. More recently, TAVI has also been shown to result in significantly lower rates of death, stroke or rehospitalisation compared with SAVR in patients with low surgical risk. As such, we can expect an increase in the number of TAVI procedures in future. Infective endocarditis is a potential complication following TAVI insertion. The rate of infective endocarditis following TAVI has been variably reported between 1 and 3%, which is similar to the rate of prosthetic valve endocarditis (PVE) following SAVR. However, the microbiology of post-TAVI endocarditis is notably different from PVE or native valve infective endocarditis, with a predominance of Enterococci. The reasons for this difference have not been elucidated but may relate to the transfemoral approach utilised for the majority of TAVIs. This raises the possibility of periprocedural bacteraemia and subsequent seeding of the newly placed valve prosthesis. To date there have been no studies investigating the rate of periprocedural bacteraemia in patients undergoing TAVI. There is a paucity of literature surrounding antibiotic prophylaxis for TAVI procedures. The European Society of Cardiology guidelines advise that antibiotic prophylaxis should be considered in patients undergoing TAVI but give no recommendation as to the agent or duration. Cefazolin is frequently used as prophylaxis for cardiothoracic surgery and a number of institutions have extrapolated this to TAVI prophylaxis. However, little is known about the pharmacokinetics (PK) and pharmacodynamics (PD) of antibiotics including cefazolin in the TAVI population, in whom there are presumably dramatic changes in haemodynamics and organ perfusion periprocedurally. Furthermore, the predominance of Enterococci in post-TAVI endocarditis would suggest that cephalosporins are a suboptimal prophylactic antibiotic. In this study, we aim to explore the incidence of periprocedural bacteraemia in patients undergoing TAVI as a possible explanation for the unique microbiological profile of infective endocarditis in this group. Additionally, we will examine demographic and procedural data for associations with any observed bacteraemia. Given the unique haemodynamic changes observed during TAVI procedures we will also examine the PK profile of prophylactic antibiotics and correlate this with any observed bacteraemia.

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