AbstractIntroduction: Balloon aortic valvuloplasty (BAV) has been used in clinical practice for over 30 years, with little standardisation of the procedure despite a renaissance in interest since the introduction of transcatheter aortic valve implantation (TAVI). We investigated the BAV procedure firstly to characterise the stroke risk with a focus on repeated balloon inflations. Secondly, we investigated the effect of serial balloon inflations on improvement of valve function during BAV procedures. Finally we investigated the inflation characteristics of valvuloplasty balloons commonly used today.
Methods: Transcranial doppler (TCD) was used to detect high intensity transient signals (HITS) at each stage of a BAV procedure as a marker of stroke risk in 38 patients undergoing BAV during TAVI procedures. A further 17 patients undergoing BAV as a standalone procedure had monitoring of intraprocedural haemodynamics to assess the effect of serial balloon inflations on valve function and calculated valve area. Finally a bespoke bright field microscopy optical measuring set up was devised to accurately measure valvuloplasty balloon diameter as a function of inflation pressure.
Results: HITS were detected at every stage during valvuloplasty procedures, peaking during balloon inflation and wire exchange into the left ventricle. The number of HITS associated with balloon inflations decreased with each serial inflation of the valvuloplasty balloon. There was no association of HITS with the degree of aortic valve calcification. Aortic valve area and transvalvular gradient improved with each satisfactory inflation of the balloon during BAV. Finally pressure vs diameter curves were generated for 3 commonly used valvuloplasty balloons demonstrating differing compliance and consistency in inflation size between serial inflations.
Conclusion: This study demonstrates that there is a risk of embolic stroke at every stage of BAV procedures, but that a lower risk is present with each serial inflation should multiple inflations be performed during the procedure. We also demonstrate that despite adequate balloon inflations, serial inflations of the BAV balloon across the aortic valve improve valve gradient and valve area. Finally, the characteristics of valvuloplasty balloons have been demonstrated to aid balloon choice and sizing during BAV procedures. Taken together this study suggests that a strategy of multiple balloon inflations should be used to maximise the impact of the procedure, and that this can be achieved without an unacceptable exposure to greater risk of stroke.
|Date of Award||May 2021|
|Supervisor||David Hildick-Smith (Supervisor) & Dr James Cockburn (Supervisor)|