Quantification of paravalvular leaks associated with TAVI implants using 4D MRI in an aortic root phantom made possible by the use of 3D printing

Abstract

IntroductionTranscatheter aortic valve implantation (TAVI) has become an alternative to surgical replacement of the aortic valve elderly patients. However, TAVI patients may suffer from paravalvular leaks (PVL). Detecting and grading is usually done by echocardiography, but is limited by resolution, 2D visualization and operator dependency. 4D flow magnetic resonance imaging (MRI) is a promising alternative, which did not reach clinical application in TAVI patients. The aim of this study was applying 3D printing technologies in order to evaluate flow patterns and hemodynamics of PVLs following TAVI, exploiting 4D flow MRI and standard ultrasound.Materials and methodsAn MR-compatible, anatomically left ventricle, aortic root, and ascending aorta model was fabricated by combining 3D-printed parts and various soft silicone materials to match physiological characteristics. An Abbott Portico™ valve was used in continuous antegrade flow (12–22 l/min), retrograde flow with varying transvalvular pressures (60–110 mmHg), and physiological pulsatile hemodynamics (aortic pressure: 120/80 mmHg, cardiac output: 5 l/min) Time-resolved MR measurements were performed above and below the TAVI stent and compared with color Doppler ultrasound measurements in exactly the same setup.ResultsThe continuous antegrade flow measurements from MRI largely agreed with the flowmeter measurements, and a maximum error of only 7% was observed. In the retrograde configuration, visualization of the paravalvular leaks was possible from the MR measurements, but flow was overestimated by up to 33%. The 4D MRI measurement in the pulsatile setup revealed a single main PVL, which was also confirmed by the color Doppler measurements, and velocities were similar (2.0 m/s vs. 1.7 m/s).Discussion4D MRI techniques were used to qualitatively assess flow in a patient-specific, MR-compatible and flexible model, which only became possible through the use of 3D printing techniques. Flow patterns in the ascending aorta, identification and quantification of PVLs was possible and the location and extent of PVLs were confirmed by ultrasound measurements. The 4D MRI flow technique allowed evaluation of flow patterns in the ascending aorta and the left ventricle below the TAVI stent with good results in identifying PVLs, demonstrating its capabilities over ultrasound by providing the ability to visualize the paravalvular jets in three dimensions at however, additional expenditure of time and money.

Four-Dimensional Flow MRI for the Evaluation of Aortic Endovascular Graft: A Pilot Study

“…Several recent studies have examined the feasibility of studying a 4D flow in transcatheter aortic valve implantation. Aigner et al concluded that utilizing 4D MRI techniques, which allow for qualitative flow assessment in a patient-specific, MR-compatible, and flexible model, was achievable through 3D printing techniques [ 33 ]. An in vivo study demonstrated flow modifications in the ascending aorta following transcatheter aortic valve implantation, particularly highlighting an asymmetric distribution of systolic wall shear stress in the ascending aorta [ 34 , 35 ].…”

The Application of Precision Medicine in Structural Heart Diseases: A Step towards the Future

“…3D printing seems to have several applications in the management of post-TAVI paravalvular leakage. Recently, Aigner and colleagues utilized 3D printing technologies to evaluate flow patterns and hemodynamics of PVLs following TAVI by exploiting 4D flow MRI and standard ultrasound [39]. A physiologically accurate, MR-compatible model of the left ventricle, aortic root, and ascending aorta was crafted through a combination of 3D-printed components and diverse soft silicone materials [39].…”

“…Recently, Aigner and colleagues utilized 3D printing technologies to evaluate flow patterns and hemodynamics of PVLs following TAVI by exploiting 4D flow MRI and standard ultrasound [39]. A physiologically accurate, MR-compatible model of the left ventricle, aortic root, and ascending aorta was crafted through a combination of 3D-printed components and diverse soft silicone materials [39]. Utilizing an Abbott Por-tico™ valve, the model underwent continuous and retrograde flows, varying transvalvular pressures, and physiological pulsatile hemodynamics for comprehensive time-resolved magnetic resonance measurements, which were subsequently compared to color Doppler ultrasound measurements within an identical experimental setup [39].…”

“…A physiologically accurate, MR-compatible model of the left ventricle, aortic root, and ascending aorta was crafted through a combination of 3D-printed components and diverse soft silicone materials [39]. Utilizing an Abbott Por-tico™ valve, the model underwent continuous and retrograde flows, varying transvalvular pressures, and physiological pulsatile hemodynamics for comprehensive time-resolved magnetic resonance measurements, which were subsequently compared to color Doppler ultrasound measurements within an identical experimental setup [39]. Continuous antegrade flow measurements from MRI closely concurred with flowmeter measurements, displaying a maximum error of merely 7%, while in the retrograde configuration, magnetic resonance visualization detected paravalvular leaks with a potential flow overestimation of up to 33% [39].…”

Analysis of fibrocalcific aortic valve stenosis: computational pre-and-post TAVR haemodynamics behaviours

“…Different studies have attempted to measure and validate PVL and its pathways, for different calcium disease morphologies. Three-dimensional printing techniques were used to assess the flow patterns and haemodynamics of PVL post-TAVR severity and were evaluated using computational fluid dynamics (CFD), and verified by utilizing four-dimensional flow magnetic resonance imaging (MRI) [ 20 ] or patient-specific in vitro replicas [ 21 ]. No correlation was found between the implantation depth and the extent of PVL [ 22 ].…”