The Woodruff School

SUMMARY

Bicuspid aortic valve (BAV) is the most common congenital heart defect and is associated with aortic stenosis (AS) which requires replacement of the native valve. Replacements are delivered through either surgical or transcatheter aortic valve replacement (TAVR) approaches. Two of the main concerns when treating BAV patients with TAVR are paravalvular leak (PVL), a known associate of increased patient mortality, and long-term durability. Additionally, stent asymmetry and undersizing are common in BAV patients both being indicators of reduced device durability. Determining the risk of these complications based on BAV anatomy is very difficult as current morphology classification systems do not encompass all aspects of the anatomy. The impact of device placement and balloon filling volume across varying BAV anatomies is also not fully understood. This work aims to contribute to answering these clinical unknowns with the overarching goal of better understanding TAVR biomechanics in BAV patients. The aortic valve and aortic arch were parametrically quantified and a classification framework was developed for each. Simulation models of the stent deployment, bioprosthetic leaflet pressurization, and PVL were developed and used to assess the device functionality following simulated patient-specific device implantation. BAV patients were found to have worsened device deformation and leaflet functionality compared to tricuspid patients. BAV patients that had excessive calcification or abnormal anatomies lead to the worst outcomes. Several mechanisms for PVL were found which were caused by non-symmetric features of the BAV anatomy. Simulations of varying TAVR strategies were tested. Lower balloon filling volume led to worsened device deformation and leaflet functionality and increased PVL. PVL was reduced with a higher deployment depth. Finally, clinical translation of the developed models was demonstrated through model use to guide clinical planning of TAVR treatment for a BAV patient with an extremely large annulus. The outcomes of this thesis can help clinicians better analyse BAV anatomy, select BAV patients for TAVR, and choose optimal TAVR strategies when treating BAV patients.

SUBJECT:	Ph.D. Dissertation Defense

BY:	Breandan Yeats

TIME:	Tuesday, April 11, 2023, 10:00 a.m.

PLACE:	Virtual, Zoom

TITLE:	Biomechanics of Transcatheter Aortic Valve Replacement for Bicuspid Aortic Valves

COMMITTEE:	Lakshmi Prasad Dasi, Chair (PhD) Ajit Yoganathan (PhD) John Oshinski (PhD) Rudolph Gleason (PhD) Vinod H. Thourani (MD)

SUMMARY Bicuspid aortic valve (BAV) is the most common congenital heart defect and is associated with aortic stenosis (AS) which requires replacement of the native valve. Replacements are delivered through either surgical or transcatheter aortic valve replacement (TAVR) approaches. Two of the main concerns when treating BAV patients with TAVR are paravalvular leak (PVL), a known associate of increased patient mortality, and long-term durability. Additionally, stent asymmetry and undersizing are common in BAV patients both being indicators of reduced device durability. Determining the risk of these complications based on BAV anatomy is very difficult as current morphology classification systems do not encompass all aspects of the anatomy. The impact of device placement and balloon filling volume across varying BAV anatomies is also not fully understood. This work aims to contribute to answering these clinical unknowns with the overarching goal of better understanding TAVR biomechanics in BAV patients. The aortic valve and aortic arch were parametrically quantified and a classification framework was developed for each. Simulation models of the stent deployment, bioprosthetic leaflet pressurization, and PVL were developed and used to assess the device functionality following simulated patient-specific device implantation. BAV patients were found to have worsened device deformation and leaflet functionality compared to tricuspid patients. BAV patients that had excessive calcification or abnormal anatomies lead to the worst outcomes. Several mechanisms for PVL were found which were caused by non-symmetric features of the BAV anatomy. Simulations of varying TAVR strategies were tested. Lower balloon filling volume led to worsened device deformation and leaflet functionality and increased PVL. PVL was reduced with a higher deployment depth. Finally, clinical translation of the developed models was demonstrated through model use to guide clinical planning of TAVR treatment for a BAV patient with an extremely large annulus. The outcomes of this thesis can help clinicians better analyse BAV anatomy, select BAV patients for TAVR, and choose optimal TAVR strategies when treating BAV patients.