Blood Flow Through The Bioprothetic Aortic Valve: Blood Flow Visualization And Energy Dynamics Based On 4d Flow Mri
Rina Makino1, Keiichi Itatani1, Satoshi Numata1, Sachiko Yamazaki1, Kazuki Morimoto1, Suguru Ohira1, Haruka Hu1, Shohei Miyazaki2, Teruyasu Nishino2, Kosuke Nakaji1, Kei Yamada1, Hitoshi Yaku1.
1Kyoto Prefectural Unversity of Medicine, Kyoto, Japan, 2Cardio Flow Design Inc., Tokyo, Japan.
OBJECTIVE: To evaluate flow characteristics of the bioprothetic aortic valve including porcine aortic and bovine pericardial valve based on 4D flow MRI. Flow energy loss (EL) through the aortic valve and output kinetic energy (KE) at the ascending aorta were estimated from the visualized blood flow.
METHODS: Two healthy volunteers and five patients after the aortic valve replacement (AVR) were examined with 4D flow MRI (3D time-resolved flow magnetic resonance imaging): 2 cases with bovine pericardium valve (Carpontier-Edwards Perimount Magna) (21 and 25 mm), and 3 cases with porcine aortic valve (Medtronic Mosaic Ultra) (23 mm in 2 cases and 27 mm in one case). Cardiovascular lumen was extracted with superposed steady-state free precession (SSFP) series for pulsatile 3D flow visualization. From the measured flow, output KE at the ascending aortic level, and flow EL through the aortic valve were calculated.
RESULTS: The age of healthy volunteer, AVR with bovine pericardium valve, and AVR with porcine aortic valve were 35.5±2.1, 77.5±5.0, and 73.7±8.7 years old, respectively. The flow rate of these tree groups were 5.10±0.49, 3.03±0.01, and 3.39±0.18 L/min, respectively.
The flow streamline of the healthy volunteers were slightly helical flow along with the arch curve (Fig. A), and EL and KE were 1.62±0.54 and 5.13±3.39 mW, respectively. The flow streamline through the bovine pericardium valve became straightforward and collided with the distal portion of the ascending aortic wall, resulting in vertical vortex inside the ascending aorta (Fig. B), and EL and KE were 2.98±0.53, and 3.95±0.21 mW. The flow streamline through the porcine aortic valve was highly helical flow inside the ascending aorta (Fig. C), and EL and KE were 3.39±1.09 and 5.82 ±3.00 mW.
CONCLUSIONS: Bioprothetic aortic valve made characteristic flow pattern depending on the porcine aortic valve or bovine pericardium valve. Compared with the normal control, flow through the bioprothetic aortic valve caused high EL. Helical flow inside the ascending aorta caused high KE output.
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