Bioprosthetic aortic valve degeneration evaluated by 18F-fluoride PET-TC
Authors: Fernandez M A , Loza G , Parma G , Florio L , Niell N , Alonso O , Ezquerra V , Robaina R , Dayan V 
Published: November 2023

Abstract

Background
Implantation of bioprosthetic aortic valves (BPHV) is increasing owing to the aging population and the emergence of transcatheter aortic valve implantation. Along with the increase in life expectancy, BPHV degeneration is therefore becoming an increasing problem. 18F-fluoride positron emission tomography (PET) has emerged as a method that could identify early subclinical BPHV degeneration.

Purpose
We aimed to compare early PET parameters of fluorid uptake with echocardiographic hemodynamic parameters at three years after the implantation of a bioprosthetic aortic valve.

Methods
Sub-analysis of the ANTIPRO clinical trial. Patients undergoing aortic valve replacement (AVR) for porcine bioprosthesis were recruited at two surgical centers between 01/01/2019 and 02/13/2020, and were randomized in two groups (acetylsalicylic acid (ASA) vs ASA and oral anticoagulation for 3 months). Clinical and echocardiographic controls were performed one year and three years after AVR. Bioprosthetic valve deterioration (BVD) was defined according to the Valve Academic Research Consortium 3. 43 subjects were randomly selected from the whole cohort to undergo 18F-sodium fluoride PET with CT angiography (PET-CT) at follow-up. 18F-fluoride uptake in the valve (SUVavV) and right atrium (SUVavA) was measured, creating the SUVavV/SUVavA ratio or target-to-background ratio (TBR). PET findings were categorized as "high uptake" if TBR &gt; 1.3 and "low uptake" if TBR ≤1.3. TBR was compared with the mean and maximum gradients at three years. Survival between high and low uptake groups was calculated using Kaplan-Meier and compared with log-rank test. The project was approved by the national ethics committee and patients consented the procedure.

Results
18F-sodium fluoride PET-CT was performed on 43 subjects, with a mean time of 22.7±8.4 months after AVR. The echocardiogram at three years was performed in a mean time of 39.9±3.0 months after AVR. Mean time between PET-CT and echocardiogram was 17.2±9.9 months.
The mean TBR was 1.25±0.30. Low uptake was found in 27 patients (62.8%) and high uptake in 15 patients (34.9%). Uptake could not be quantified in one patient due to technical problems.
Baseline characteristics were similar between both groups (Table 1).
Mean gradient at three years was 19.6±10.3 and peak gradient 33.7±16.7. Mean gradient was similar between the high uptake and low uptake groups (17.5±11.7 vs 21.6±9.3 p=0.296). Peak gradient was also similar between the high uptake and low uptake groups (30.6±18.5 vs 36.3±15.6 p=0.362). Five patients experienced BVD, of which 4 had low uptake and 1 had high uptake (p=0.523).
Survival analysis did not demonstrate statistically different survival rates between the high uptake and low uptake groups (Figure 1).

Conclusion
Fluorid uptake with early PET after AVR was not associated with trans-prosthetic gradients nor BVD after a mean of 17 months from the PET scan.Table 1:Baseline characteristicsFigure 1:Kaplan-Meier survival curve