Structural analysis of regional transcatheter aortic valve underexpansion and its implications for subclinical leaflet thrombosis

Abstract

Subclinical leaflet thrombosis has been increasingly recognized following transcatheter aortic valve replacement (TAVR). Determining the risk factors is vital in preventing clinical leaflet thrombosis and ensuring long-term value durability. Clinical data have indicated that regional stent under-expansion of transcatheter aortic valves (TAVs), particularly self-expanding devices, may be associated with an increased risk of subclinical leaflet thrombosis. This study aimed to determine the effects of regional TAV frame under-expansion on leaflet kinematics, leaflet structural characteristics, and explore its impact on the likelihood of leaflet thrombosis. In this study, mild and moderate regional frame under-expansion of a 26-mm CoreValve were examined using experimental testing and computational simulations. The results indicated that regional TAV frame under-expansion impairs leaflet kinematics and reduces the range of motion in leaflets with an angle less than 120 . The reduced range of motion can increase blood stasis on the surface of the TAV leaflets. The results also demonstrated that regional frame under-expansion induced localized high-stress regions in the leaflets close to the fixed boundary edge. The increased mechanical stress can lead to accelerated tissue degeneration. The study improves our understanding of the effects of regional stent underexpansion in TAVR. Post-procedural balloon dilatation of self-expanding TAVs can potentially be advantageous in reducing leaflet distortion and normalizing leaflet stress distribution. Large-scale, prospective, and well-controlled studies are needed to further investigate regional TAV frame under-expansion effects on subclinical leaflet thrombosis and long-term valve durability.finite element modeling, regional stent under-expansion, transcatheter heart valve replacement, valve oversizing | INTRODUCTIONTranscatheter aortic valve replacement (TAVR) is a safe and effective treatment for patients with severe symptomatic aortic stenosis. TAVR is approved across all risk profiles, and the number of eligible patients is growing rapidly. Despite

The Effect of Bileaflet Mechanical Heart Valve Designs on Biomechanical Behaviours – A Finite Element Analysis

“…Travis et al, 2008 [39] in their experimental work claimed that viscous stress was significantly affected by a large hinge gap where this situation may contribute to more damages to the blood cell and increase the risk of thromboembolic complications. Besides, the retraction mechanism of the expandable housing that allows the part to move back into its original position gives a potential of blood backflow and thrombosis to occur [28]. Blood backflow may impose harms to patients namely shortness of breath which attributes the heart to be dilated and pumped vigorously.…”

“…During the maximum opening and closing of the valve leaflets, blood with high velocity jets through the gap between the leaflet and the housing attributing the mechanical stress to elevate and may subsequently cause red blood cell damage and platelet activation. On top of that, an increase in the coagulation due to blood stagnancy with the artery wall may lead to thrombosis and thromboembolism which should be avoided for cardiac patients [28]. Countless cyclic leaflet motions could reduce the structural strength of the heart valve, develop inhomogeneous mechanical properties of the leaflet, and initiate the cavitation phenomenon to occur [29].…”

Left atrial appendage occlusion: On the need of a numerical model to simulate the implant procedure

“…Namely, the location of the ostium with respect to the point where the clinician punctures the fossa ovalis strictly affects the final positioning of the access/delivery system, leading to either an optimal positioning or several suboptimal positioning, as schematized in Figure 1. In the following, the five parameters are presented: Device oversize: the oversizing, together with the presence of the hooks, is essential in securing the device in situ, and minimizing blood leaks, as observed also for other interventional procedures 14,32 . For the sake of convenience, the LAAO implant guidelines consider the maximum device diameter (, Figure 2A) as the reference dimension to assign a size to the device.…”

“…7,[9][10][11][12][13] In the field of transcatheter heart interventions, as the LAAO, the standard procedure followed by the clinician to select the most suitable interventional strategy is represented by the use of imaging techniques. Over the past decades, 3D-printed anatomical phantoms and, more recently, computational models have been recognized with great potential in identifying the risk factors associated with a percutaneous cardiac procedure 14 and guiding clinical choices. The support of numerical tools leads to an even more patient-centric intervention and allows for improvement and prediction of procedural outcomes.…”

“…Device oversize: the oversizing, together with the presence of the hooks, is essential in securing the device in situ, and minimizing blood leaks, as observed also for other interventional procedures. 14,32 For the sake of convenience, the LAAO implant guidelines consider the maximum device diameter (d device , Figure 2A) as the reference dimension to assign a size to the device. The most suitable DO must be selected to allow a compression range of the device from 10% to 30% while working in vivo.…”