4D Flow MRI hemodynamic benchmarking of surgical bioprosthetic valves

Abstract

We exploited 4-dimensional flow magnetic resonance imaging (4D Flow), combined with a standardized in vitro setting, to establish a comprehensive benchmark for the systematic hemodynamic comparison of surgical aortic bioprosthetic valves (BPVs). Materials and methods: 4D Flow analysis was performed on two small sizes of three commercialized pericardial BPVs (Trifecta™ GT, Carpentier-Edwards PERIMOUNT Magna and Crown PRT®). Each BPV was tested over a clinically pertinent range of continuous flow rates within an in vitro MRI-compatible system, equipped with pressure transducers. In-house 4D Flow post-processing of the post-valvular velocity field included the quantification of BPV effective orifice area (EOA), transvalvular pressure gradients (TPG), kinetic energy and viscous energy dissipation. Results: The 4D Flow technique effectively captured the 3-dimensional flow pattern of each device. Trifecta exhibited the lowest range of velocity and kinetic energy, maximized EOA (p < 0.0001) and minimized TPGs (p ≤ 0.015) if compared with Magna and Crown, these reporting minor EOA difference s (p ≥ 0.042) and similar TPGs (p ≥ 0.25). 4D Flow TPGs estimations strongly correlated against ground-truth data from pressure transducers; viscous energy dissipation proved to be inversely proportional to the fluid jet penetration. Conclusion:The proposed 4D Flow analysis pinpointed consistent hemodynamic differences among BPVs, highlighting the not negligible effect of device size on the fluidynamic outcomes. The efficacy of non-invasive 4D Flow MRI protocol could shed light on how standardize the comparison among devices in relation to their actual hemodynamic performances and improve current criteria for their selection.

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

“…The VENC parameters were set based on the measured velocity so that there were no phase wraps, not only on expected jet velocities. To avoid velocity aliasing, long-axis scout sequences were used to improve and optimally adjust the original estimated values [10% higher than the estimated maximum speed parallel to the flow direction ( 18 ); see Table 4 ]. Pulsatile acquisitions were split into the systolic and diastolic phase to investigate the forward as well as the regurgitant flow.…”

“…For continuous flow settings the entire volume was averaged in three consecutive acquisitions to improve the signal-to-noise ratio. In addition, the kinetic energy content of the PVLs jet was calculated based on the equation , (ρ: density of the fluid, V i : volume of each voxel, v : is the velocity) which is a measure of the conversion of static to kinetic energy ( 18 ).…”

Computational hemodynamic indices to identify Transcatheter Aortic Valve Implantation degeneration

“…Prescribing completely patient-specific inlet conditions can be achieved by exploiting 4D-Flow Magnetic Resonance Imaging [48]. This could not be done in the present work due to the retrospective nature of the study.…”

“…We plan to provide a wire-frame design for the aortic side of the stent in future studies; -Including patient-specific information concerning only mean flow rates in the boundary conditions. Prescribing completely patient-specific inlet conditions can be achieved by exploiting 4D-Flow Magnetic Resonance Imaging [48]. This could not be done in the present work due to the retrospective nature of the study.…”

Συγκριτική αξιολόγηση in vitro της λειτουργίας διαφόρων τύπων προσθετικών βαλβίδων μιτροειδούς με τη χρήση νεότερων απεικονιστικών τεχνικών

“…Σε ενίσχυση του συμπεράσματος αυτού, πρόσφατη μελέτη που πραγματοποιήθηκε σε βιοπροσθετικές βαλβίδες τοποθετημένες σε ομοίωμα αορτικής ρίζας με χρήση in vitro πειραματικού μοντέλου σταθερής ροής, έδειξε ότι η επιφάνεια του λειτουργικού στομίου είναι δυνατόν να υπολογιστεί με την 4D Flow MRI, παρουσιάζοντας καλή συσχέτιση και συμφωνία κατά την σύγκρισή της με την επιφάνεια του λειτουργικού στομίου που είχε υπολογιστεί με την εξίσωση Gorlin. [89] Παρά το γεγονός ότι επί του παρόντος το κυριότερο εργαλείο για την εκτίμηση της αιματικής ροής ενδοκαρδιακά είναι η Doppler υπερηχοκαρδιογραφία -παρέχοντας την δυνατότητα να μετρά την ταχύτητα της ροής στην κατεύθυνση της δέσμης των υπερήχων ή εξασφαλίζοντας την δισδιάστατη απεικόνιση της αιματικής ροής σε μία κατεύθυνση με την χρήση του έγχρωμου Doppler-η χρήση της στους υπολογισμούς της ροής δεν παύει να υπόκειται σε περιορισμούς που αφορούν το προφίλ της ροής, το σχήμα και την επιφάνεια εισόδου και εξόδου της ροής. Τέτοιοι περιορισμοί ενδέχεται να οδηγήσουν σε επισφαλή αποτελέσματα μέτρησης, ιδίως στις σύμπλοκες περιπτώσεις ροής ή όταν η περιοχή ενδιαφέροντος εμφανίζει ιδιαιτερότητες στην ανατομία.…”