University of California San Francisco

Computational Simulation of Transcatheter Aortic Valve Replacement (TAVR)

Computational Simulation of Transcatheter Aortic Valve Replacement (TAVR)

Aortic stenosis (AS) is the most common heart valve disease encountered in the elderly. The aortic valve leaflets become restricted due to excessive calcium buildup. In the past, surgical aortic valve replacement (SAVR) was the gold standard to treat patients with severe AS, which entailed opening the chest and placing the patient on cardiopulmonary bypass.

Today, many patients are eligible for a minimally invasive alternative therapy called transcatheter aortic valve replacement (TAVR). In TAVR, an expandable bioprosthetic aortic valve is delivered to the diseased aortic valve via percutaneous access. TAVR has revolutionized the treatment of AS, and the latest PARTNER 3 and Evolut Low Risk trials show strong promise for TAVR as effective therapy for even the lowest risk patients with AS.

However, many questions remain as TAVR becomes increasingly utilized. One unanswered question is TAVR durability, which is believed to be shorter than the surgical bioprosthetic aortic valves given thinner leaflets. Over time, bioprosthetic valve leaflets will degenerate or ‘wear out’ leading to stenosis or insufficiency. Second, the entity of subclinical leaflet thrombosis has been observed in 10-15% of TAVR patients, which may place patients at risk for stroke.

Computational studies on TAVR in the Cardiac Biomechanics Lab aim to shed light on these issues. Finite element models of various generations of devices, patient-specific deployment models, and fluid structure interaction simulations will help elucidate mechanisms of TAVR complications and guide clinicians to optimal device selection.

Tavr Fig1

Figure 1: A, Regions of interest studied for stress distribution in leaflets. Region 1 ¼ upper leaflet free edges, region 2 ¼ lower leaflet belly, and region 3 ¼ sutured leaflet edges. B, Geometry of 26-mm Sapien Transcatheter Aortic Valve (Edwards Lifesciences, Irvine, Calif). C, Transcatheter aortic valve finite element mesh. (Xuan et al. J Thorac Cardiovasc Surg 2017;153:1065-73)

 

Tavr Fig2

Figure 2: Principal stresses on entire leaflet assembly at 80 mm Hg under quasistatic conditions. A, Maximum. B,Minimum. Principal stresses on entire leaflet at 120 mm Hg under quasistatic conditions. C, Maximum. D, Minimum. (Xuan et al. J Thorac Cardiovasc Surg 2017;153:1065-73)

Tavr Fig3

Figure 3: Under quasistatic loading, principal stresses of stent at 80 mm Hg. A, Maximum. B, Minimum. Under quasistatic loading, principal stresses at 120 mm Hg. C, Maximum. D, Minimum. (Xuan et al. J Thorac Cardiovasc Surg 2017;153:1065-73)

 

References

Xuan Y, Krishnan K, Ye J, Dvir D, Guccione JM, Ge L, Tseng EE. Stent and leaflet stresses in a 26-mm first-generation balloon-expandable transcatheter aortic valve. J Thorac Cardiovasc Surg 2017;153:1065-73.)