Background: There remain major uncertainties regarding disease activity within the retained native aortic valve as well as bioprosthetic valve durability following transcatheter aortic valve implantation (TAVI). We aimed to assess native aortic valve disease activity and bioprosthetic valve durability in patients with TAVI in comparison to subjects with bioprosthetic surgical aortic valve replacement (SAVR).
Methods: In a multicenter cross-sectional observational cohort study, patients with TAVI or bioprosthetic SAVR underwent baseline echocardiography, CT angiography and 18F-sodium fluoride (18F-NaF) positron emission tomography (PET). Participants (n=47) were imaged once with 18F-NaF PET/CT either at one-month (n=9, 19%), 2 years (n=22, 47%) or 5 years (16, 34%) after valve implantation. Subsequently patients underwent serial echocardiography to assess for changes in valve hemodynamic performance (change in peak aortic velocity) and evidence of structural valve dysfunction. Comparisons were made to matched patients with bioprosthetic SAVR (n=51) who had undergone the same imaging protocol.
Results: In patients with TAVI, native aortic valves demonstrated 18F-NaF uptake around the outside of the bioprostheses that showed a modest correlation with the time from TAVI (r=0.36, p=0.023). 18F-NaF uptake in the bioprosthetic leaflets was comparable between the SAVR and TAVI groups (target-to-background ratio 1.3 [1.2-1.7] versus 1.3 [1.2-1.5] respectively, p=0.27). The frequencies of imaging evidence of bioprosthetic valve degeneration at baseline were similar on echocardiography (6% versus 8% respectively, p=0.78), CT (15% versus 14% respectively, p=0.87) and PET (15% versus 29% respectively, p=0.09). Baseline 18F-NaF uptake was associated with subsequent change in peak aortic velocity for both TAVI (r=0.7, p<0.001) and SAVR (r=0.7, p<0.001). On multivariable analysis, 18F-NaF uptake was the only predictor of peak velocity progression (p<0.001).
Conclusions: In patients with TAVI, native aortic valves demonstrate evidence of ongoing active disease. Across imaging modalities, TAVI degeneration is of similar magnitude to bioprosthetic SAVR suggesting comparable mid-term durability.