Non-invasive cardiovascular magnetic resonance assessment of pressure recovery distance after aortic valve stenosis.

BACKGROUND: Decisions in the management of aortic stenosis are based on the peak pressure drop, captured by Doppler echocardiography, whereas gold standard catheterization measurements assess the net pressure drop but are limited by associated risks. The relationship between these two measurements, peak and net pressure drop, is dictated by the pressure recovery along the ascending aorta which is mainly caused by turbulence energy dissipation. Currently, pressure recovery is considered to occur within the first 40-50 mm distally from the aortic valve, albeit there is inconsistency across interventionist centers on where/how to position the catheter to capture the net pressure drop. METHODS: We developed a non-invasive method to assess the pressure recovery distance based on blood flow momentum via 4D Flow cardiovascular magnetic resonance (CMR). Multi-center acquisitions included physical flow phantoms with different stenotic valve configurations to validate this method, first against reference measurements and then against turbulent energy dissipation (respectively n = 8 and n = 28 acquisitions) and to investigate the relationship between peak and net pressure drops. Finally, we explored the potential errors of cardiac catheterisation pressure recordings as a result of neglecting the pressure recovery distance in a clinical bicuspid aortic valve (BAV) cohort of n = 32 patients. RESULTS: In-vitro assessment of pressure recovery distance based on flow momentum achieved an average error of 1.8 ± 8.4 mm when compared to reference pressure sensors in the first phantom workbench. The momentum pressure recovery distance and the turbulent energy dissipation distance showed no statistical difference (mean difference of 2.8 ± 5.4 mm, R2 = 0.93) in the second phantom workbench. A linear correlation was observed between peak and net pressure drops, however, with strong dependences on the valvular morphology. Finally, in the BAV cohort the pressure recovery distance was 78.8 ± 34.3 mm from vena contracta, which is significantly longer than currently accepted in clinical practise (40-50 mm), and 37.5% of patients displayed a pressure recovery distance beyond the end of the ascending aorta. CONCLUSION: The non-invasive assessment of the distance to pressure recovery is possible by tracking momentum via 4D Flow CMR. Recovery is not always complete at the ascending aorta, and catheterised recordings will overestimate the net pressure drop in those situations. There is a need to re-evaluate the methods that characterise the haemodynamic burden caused by aortic stenosis as currently clinically accepted pressure recovery distance is an underestimation.

4D Flow cardiovascular magnetic resonance consensus statement: 2023 update.

Hemodynamic assessment is an integral part of the diagnosis and management of cardiovascular disease. Four-dimensional cardiovascular magnetic resonance flow imaging (4D Flow CMR) allows comprehensive and accurate assessment of flow in a single acquisition. This consensus paper is an update from the 2015 '4D Flow CMR Consensus Statement'. We elaborate on 4D Flow CMR sequence options and imaging considerations. The document aims to assist centers starting out with 4D Flow CMR of the heart and great vessels with advice on acquisition parameters, post-processing workflows and integration into clinical practice. Furthermore, we define minimum quality assurance and validation standards for clinical centers. We also address the challenges faced in quality assurance and validation in the research setting. We also include a checklist for recommended publication standards, specifically for 4D Flow CMR. Finally, we discuss the current limitations and the future of 4D Flow CMR. This updated consensus paper will further facilitate widespread adoption of 4D Flow CMR in the clinical workflow across the globe and aid consistently high-quality publication standards.

Validation of pressure drop assessment using 4D flow MRI-based turbulence production in various shapes of aortic stenoses.

PURPOSE: To validate pressure drop measurements using 4D flow MRI-based turbulence production in various shapes of stenotic stenoses. METHODS: In vitro flow phantoms with seven different 3D-printed aortic valve geometries were constructed and scanned with 4D flow MRI with six-directional flow encoding (ICOSA6). The pressure drop through the valve was non-invasively predicted based on the simplified Bernoulli, the extended Bernoulli, the turbulence production, and the shear-scaling methods. Linear regression and agreement of the predictions with invasively measured pressure drop were analyzed. RESULTS: All pressure drop predictions using 4D Flow MRI were linearly correlated to the true pressure drop but resulted in different regression slopes. The regression slope and 95% limits of agreement for the simplified Bernoulli method were 1.35 and 11.99 ± 21.72 mm Hg. The regression slope and 95% limits of agreement for the extended Bernoulli method were 1.02 and 0.74 ± 8.48 mm Hg. The regression slope and 95% limits of agreement for the turbulence production method were 0.89 and 0.96 ± 8.01 mm Hg. The shear-scaling method presented good correlation with an invasively measured pressure drop, but the regression slope varied between 0.36 and 1.00 depending on the shear-scaling coefficient. CONCLUSION: The pressure drop assessment based on the turbulence production method agrees well with the extended Bernoulli method and invasively measured pressure drop in various shapes of the aortic valve. Turbulence-based pressure drop estimation can, as a complement to the conventional Bernoulli method, play a role in the assessment of valve diseases.

Multi-VENC acquisition of four-dimensional phase-contrast MRI to improve precision of velocity field measurement.

PURPOSE: The present study aims to improve precision of four-dimensional (4D) phase-contrast (PC) MRI technique by using multiple velocity encoding (VENC) parameters. THEORY AND METHODS: The 3D flow fields in an in vitro stenosis phantom and an in vivo ascending aorta were determined using a 4D PC-MRI sequence with multiple VENC values. The velocity field obtained for large VENC was combined with that from small VENC, unless velocity data were lost by phase aliasing and phase dispersion. Noise levels of the combined velocity fields were compared with the increasing overlapping number of VENC parameters. RESULTS: The phantom measurement showed that the multi-VENC acquisition reduced the noise levels in radial and axial velocities (> 24 cm/s at VENC = 300 cm/s) down to 0.80 ± 0.45 cm/s and 5.60 ± 2.63 cm/s, respectively. This increased the velocity-to-noise ratio (VNR) by approximately two-fold to six-fold depending on the locations. As a result, the multi-VENC measurement could visualize the low-velocity recirculating flows more clearly. CONCLUSION: The multi-VENC measurement of 4D PC-MRI sequence increased the VNR distribution by reducing velocity noise. The improved VNR can be beneficial for investigating blood flow structures in a flow field with a high velocity dynamic range.

Hemodynamic features and platelet aggregation in a stenosed microchannel.

Platelet aggregation has been known to be closely influenced by the surrounding hemodynamic environments. Especially, platelet activation, aggregation, and thrombus formation frequently occur at the locally stenosed blood vessel where recirculation and stagnation flow regions are developed. However, the relationship between hemodynamic feature and platelet aggregation is not fully understood yet. The main objective of this study is to investigate the hemodynamic characteristics of blood flow in a stenosis channel and their effects on platelet aggregation. Whole blood was injected into a stenosed microchannel with 85% severity at various flow rates, ranging from 10 to 50mLhr(-1). The velocity vector field of the blood flow in the stenosed microchannel was measured using newly developed LED (light emitting diode)-illumination microparticle image velocimetry (micro-PIV). The blood flow is highly disturbed by the micro-stenosis, and a recirculation flow region is formed at the post-stenosis region. The occurring site and the shape of the platelet aggregation are highly influenced by the hemodynamic characteristics of blood flow around the stenosis. Especially, the platelet aggregation is found to occur at the interface where the downward momentum of the central jet at the post-stenosis region and the upward momentum of the recirculation flow are balanced. These experimental results would be helpful to understand the platelet aggregation under disturbed blood flow conditions.

Effect of fluid viscosity on the liquid-feeding flow phenomena of a female mosquito.

Liquid-sucking phenomena by the two-pump system of female mosquitoes were investigated to understand the feeding mechanism. In most previous experimental studies on liquid-feeding insects, the net increase of mass was divided by the feeding time and fluid density to evaluate the intake rate. However, this weighting method is not so precise for mosquitoes, because they are too lightweight to measure the gain of mass accurately. In this study, the intake rate of female mosquitoes feeding on various sucrose solutions was estimated using a micro-particle image velocimetry technique. As the sucrose concentration increased from 1% to 50%, the intake rate decreased from 17.3 to 5.8 nl s(-1). In addition, the temporal volume variations of the two pump chambers were estimated based on the velocity and acceleration information of the flow at the center of the food canal of the proboscis. One pumping period was divided into four elementary phases, which are related to the different operational modes of the two pumps. According to the hypothetical model established in this study, the phase shift () between the two pump chambers increases from 14 to 28 ms and the percentage of reverse flow to forward flow in a pumping period decreases from 7.6% to 1.7% with increasing viscosity. The developed analytical methodology thus aids in the study of an insect's feeding mechanism.

Modelling and simulation of fluid flow through stenosis and aneurysm blood vessel: a computational hemodynamic analysis.

In this article, the hemodynamics of nanofluid flow through the modelled stenosis-aneurysm models in the presence of the catheter has been studied. The eight stenosis-aneurysm models are developed to mimic biological observations and thus make the model more realistic. The mathematical understanding helps in treating the stenosis in the blood vessel by targeting the unhealthy region to the drug, which is coated on nanoparticles. The catheter achieves the active drug release to the aimed organs by coating on the catheter surface, which adds additional benefits. In the present hemodynamic study, the blood is modeled as a couple stress fluid; as a result, the highly non-linear momentum, temperature, and concentration equations were obtained. The fluid flow equations' complexity is further increased by incorporating the variable viscosity effects that arose due to the suspension of nanoparticles. The resultant mathematical model is solved by using the homotopy perturbation method. The convergence of the perturbed solutions is studied and depicted the degree of deformation in the case of temperature and concentration. The effects of the porous nature of the stenosis, no-slip at the catheter surface, and the free slip at the blood vessel boundary in the non-stenotic region are also considered in the model. The essential physiological property like surface shear stress is computed, and various parameters' influence on shear stress is analyzed. The present analysis can be helpful in understanding the enhancement in mass dispersion and heat transfer in unhealthy blood vessels, which could be used for drug delivery in the treatment of stenotic conditions.

Assessing the impact of turbulent kinetic energy boundary conditions on turbulent flow simulations using computational fluid dynamics.

Computational fluid dynamics has been widely used to study hemodynamics, but accurately determining boundary conditions for turbulent blood flow remains challenging. This study aims to investigate the effect of patient-specific turbulence boundary conditions on the accuracy of turbulent flow simulation. Using a stenosis model with 50% severity in diameter, the post-stenosis turbulence flow region was simulated with different planes to obtain inlet boundary conditions and simulate downstream flows. The errors of simulated flow fields obtained with turbulence kinetic energy (TKE) boundary data and arbitrary turbulence intensity were compared. Additionally, the study tested various TKE data resolutions and noise levels to simulate experimental environments. The mean absolute error of velocity and TKE was investigated with various turbulence intensities and TKE mapping. While voxel size and signal-to-noise ratio of the TKE data affected the results, simulation with SNR > 5 and voxel size < 10% resulted in better accuracy than simulations with turbulence intensities. The simulation with appropriate TKE boundary data resulted in a more accurate velocity and turbulence field than those with arbitrary turbulence intensity boundary conditions. The study demonstrated the potential improvement of turbulent blood flow simulation with patient-specific turbulence boundary conditions, which can be obtained from recent measurement techniques.

Characterization of baseline hemodynamics after the Fontan procedure: a retrospective cohort study on the comparison of 4D Flow MRI and computational fluid dynamics.

Introduction: The aim of this study was to characterize the hemodynamics of Fontan patients using both four-dimensional flow magnetic resonance imaging (4D Flow MRI) and computational fluid dynamics (CFD). Methods: Twenty-nine patients (3.5 ± 0.5 years) who had undergone the Fontan procedure were enrolled, and the superior vena cava (SVC), left pulmonary artery (LPA), right pulmonary artery (RPA), and conduit were segmented based on 4D Flow MRI images. Velocity fields from 4D Flow MRI were used as boundary conditions for CFD simulations. Hemodynamic parameters such as peak velocity (Vmax), pulmonary flow distribution (PFD), kinetic energy (KE), and viscous dissipation (VD) were estimated and compared between the two modalities. Results and discussion: The Vmax, KE, VD, PFDTotal to LPA, and PFDTotal to RPA of the Fontan circulation were 0.61 ± 0.18 m/s, 0.15 ± 0.04 mJ, 0.14 ± 0.04 mW, 41.3 ± 15.7%, and 58.7 ± 15.7% from 4D Flow MRI; and 0.42 ± 0.20 m/s, 0.12 ± 0.05 mJ, 0.59 ± 0.30 mW, 40.2 ± 16.4%, and 59.8 ± 16.4% from CFD, respectively. The overall velocity field, KE, and PFD from the SVC were in agreement between modalities. However, PFD from the conduit and VD showed a large discrepancy between 4D Flow MRI and CFD, most likely due to spatial resolution and data noise. This study highlights the necessity for careful consideration when analyzing hemodynamic data from different modalities in Fontan patients.

Fluid-structure interaction simulation of visceral perfusion and impact of different cannulation methods on aortic dissection.

Hemodynamics in aortic dissection (AD) is closely associated with the risk of aortic aneurysm, rupture, and malperfusion. Altered blood flow in patients with AD can lead to severe complications such as visceral malperfusion. In this study, we aimed to investigate the effect of cannulation flow on hemodynamics in AD using a fluid-structure interaction simulation. We developed a specific-idealized AD model that included an intimal tear in the descending thoracic aorta, a re-entry tear in the left iliac artery, and nine branches. Two different cannulation methods were tested: (1) axillary cannulation (AC) only through the brachiocephalic trunk and (2) combined axillary and femoral cannulation (AFC) through the brachiocephalic trunk and the right common iliac artery. AC was found to result in the development of a pressure difference between the true lumen and false lumen, owing to the difference in the flow rate through each lumen. This pressure difference collapsed the true lumen, disturbing blood flow to the celiac and superior mesenteric arteries. However, in AFC, the pressure levels between the two lumens were similar, and no collapse occurred. Moreover, the visceral flow was higher than that in AC. Lastly, the stiffness of the intimal flap affected the true lumen's collapse.

Hybrid PIV-PTV technique for measuring blood flow in rat mesenteric vessels.

The micro-particle tracking velocimetry (µ-PTV) technique is used to obtain the velocity fields of blood flow in the microvasculature under in vivo conditions because it can provide the blood velocity distribution in microvessels with high spatial resolution. The in vivo µ-PTV technique usually requires a few to tens of seconds to obtain a whole velocity profile across the vessel diameter because of the limited number density of tracer particles under in vivo conditions. Thus, the µ-PTV technique alone is limited in measuring unsteady blood flows that fluctuate irregularly due to the heart beating and muscle movement in surrounding tissues. In this study, a new hybrid PIV-PTV technique was established by combining PTV and particle image velocimetry (PIV) techniques to resolve the drawbacks of the µ-PTV method in measuring blood flow in microvessels under in vivo conditions. Images of red blood cells (RBCs) and fluorescent particles in rat mesenteric vessels were obtained simultaneously. Temporal variations of the centerline blood velocity were monitored using a fast Fourier transform-based cross-correlation PIV method. The fluorescence particle images were analyzed using the µ-PTV technique to extract the spatial distribution of the velocity vectors. Data from the µ-PTV and PIV methods were combined to obtain a better estimate of the velocity profile in actual blood flow. This technique will be useful in investigating hemodynamics in microcirculation by measuring unsteady irregular blood flows more accurately.

Particle Image Velocimetry Investigation of Hemodynamics via Aortic Phantom.

Aortic valve dysfunction and stroke have recently been reported in transcatheter aortic valve implantation (TAVI) patients. Thrombus in the aortic sinus and neo-sinus due to hemodynamic changes has been suspected. In vitro experiments help investigate the hemodynamic characteristics in the cases where an in vivo assessment proves to be limited. In vitro experiments are also more robust, and the variable parameters are controlled readily. Particle image velocimetry (PIV) is a popular velocimetry method for in vitro studies. It provides a high-resolution velocity field such that even small-scale flow features are observed. The purpose of this study is to show how PIV is used to investigate the flow field in the aortic sinus after TAVI. The in vitro setup of the aortic phantom, TAVI for PIV, and the data acquisition process and post-processing flow analysis are described. The hemodynamic parameters are derived, including the velocity, flow stasis, vortex, vorticity, and particle residence. The results confirm that in vitro experiments and PIV help investigate the hemodynamic features in the aortic sinus.

In vitro Assessment of Aortic Regurgitation Using Four-Dimensional Flow Magnetic Resonance Imaging.

Aortic regurgitation (AR) refers to backward blood flow from the aorta into the left ventricle (LV) during ventricular diastole. The regurgitant jet arising from the complex shape is characterized by the three-dimensional flow and high-velocity gradient, sometimes limiting an accurate measurement of the regurgitant volume using 2D echocardiography. Recently developed four-dimensional flow magnetic resonance imaging (4D flow MRI) enables three-dimensional volumetric flow measurements, which can be used to accurately quantify the amount of the regurgitation. This study focuses on (i) magnetic resonance compatible AR model fabrication (dilatation, perforation, and prolapse) and (ii) systematic analysis of the performance of 4D flow MRI in AR quantification. The results indicated that the formation of the forward and backward jets over time was highly dependent on the types of AR origin. The amount of regurgitation volume bias for the model types were -7.04%, -33.21%, 6.75%, and 37.04% compared to the ground truth (48 mL) volume measured from the pump stroke volume. The largest error of the regurgitation fraction was around 12%. These results indicate that careful selection of imaging parameters is required when absolute regurgitation volume is important. The suggested in vitro flow phantom can easily be modified to simulate other valvular diseases such as aortic stenosis or bicuspid aortic valve (BAV) and can be used as a standard platform to test different MRI sequences in the future.

Quantification of visceral perfusion and impact of femoral cannulation: in vitro model of aortic dissection.

OBJECTIVES: We aimed to simulate blood flow at an aortic dissection in an in vitro vascular model and assess the impact of the cannulation method on visceral perfusion. METHODS: An aortic-dissection model with an acrylic aortic wall and silicone intimal flap was developed to study visceral perfusion under various cannulation conditions. The primary tear was placed in the proximal descending aorta and the re-entry site in the left common iliac artery. A cardiovascular pump was used to reproduce a normal pulsatile aortic flow and a steady cannulation flow. Axillary and axillary plus femoral cannulation were compared at flow rates of 3-7 l/min. Haemodynamics were analysed by using four-dimensional flow magnetic resonance imaging. RESULTS: Axillary cannulation (AC) was found to collapse the true lumen at the coeliac and superior mesentery arteries, while combined axillary and femoral cannulation did not change the size of the true lumen. Combined axillary and femoral cannulation resulted in a larger visceral flow than did AC alone. When axillary plus femoral cannulation was used, the visceral flow increased by 125% at 3 l/min, by 89% at 4 l/min, by 67% at 5 L/min, by 98% at 6 l/min and by 101% at 7 l/min, respectively, compared to those with the AC only. CONCLUSIONS: Our model was useful to understanding the haemodynamics in aortic dissection. In this specific condition, we confirmed that the intimal flap motion can partially block blood flow to the coeliac and superior mesenteric arteries and that additional femoral cannulation can increase visceral perfusion.

Cardiac outflow and wall motion in hypothermic chick embryos.

Cardiac outflow in the early developmental stage of a chick embryo is known to be highly variable depending on environmental temperature. To investigate the effects of environmental hypothermia on the blood flow in the outflow tract (OFT) of chick embryonic hearts, microscopic flow images were consecutively captured from chick embryos at HH stage 17 (2.5 days of incubation) at room temperature. Instantaneous velocity field information of blood flow in OFT was obtained using a micro-particle image velocimetry technique. The cyclic variations of the OFT vessel diameter and wall thickness were simultaneously measured. The experimental results show that environmental hypothermia causes bradycardia with a decrease in peak velocity during systole and the occurrence of backflow during diastole in the OFT. These abnormal phenomena seem to be attributed to the suppression of myocardial wall motion under hypothermic conditions.

Improving Blood Flow Visualization of Recirculation Regions at Carotid Bulb in 4D Flow MRI Using Semi-Automatic Segmentation with ITK-SNAP.

Assessment of carotid bulb hemodynamics using four-dimensional (4D) flow magnetic resonance imaging (MRI) requires accurate segmentation of recirculation regions that is frequently hampered by limited resolution. This study aims to improve the accuracy of 4D flow MRI carotid bulb segmentation and subsequent recirculation regions analysis. Time-of-flight (TOF) MRI and 4D flow MRI were performed on bilateral carotid artery bifurcations in seven healthy volunteers. TOF-MRI data was segmented into 3D geometry for computational fluid dynamics (CFD) simulations. ITK-SNAP segmentation software was included in the workflow for the semi-automatic generation of 4D flow MRI angiographic data. This study compared the velocities calculated at the carotid bifurcations and the 3D blood flow visualization at the carotid bulbs obtained by 4D flow MRI and CFD. By applying ITK-SNAP segmentation software, an obvious improvement in the 4D flow MRI visualization of the recirculation regions was observed. The 4D flow MRI images of the recirculation flow characteristics of the carotid artery bulbs coincided with the CFD. A reasonable agreement was found in terms of velocity calculated at the carotid bifurcation between CFD and 4D flow MRI. However, the dispersion of velocity data points relative to the local errors of measurement in 4D flow MRI remains. Our proposed strategy showed the feasibility of improving recirculation regions segmentation and the potential for reliable blood flow visualization in 4D flow MRI. However, quantitative analysis of recirculation regions in 4D flow MRI with ITK-SNAP should be enhanced for use in clinical situations.

Comparison of Hemodynamic Visualization in Cerebral Arteries: Can Magnetic Resonance Imaging Replace Computational Fluid Dynamics?

A multimodality approach was applied using four-dimensional flow magnetic resonance imaging (4D flow MRI), time-of-flight magnetic resonance angiography (TOF-MRA) signal intensity gradient (SIG), and computational fluid dynamics (CFD) to investigate the 3D blood flow characteristics and wall shear stress (WSS) of the cerebral arteries. TOF-MRA and 4D flow MRI were performed on the major cerebral arteries in 16 healthy volunteers (mean age 34.7 ± 7.6 years). The flow rate measured with 4D flow MRI in the internal carotid artery, middle cerebral artery, and anterior cerebral artery were 3.8, 2.5, and 1.2 mL/s, respectively. The 3D blood flow pattern obtained through CFD and 4D flow MRI on the cerebral arteries showed reasonable consensus. CFD delivered much greater resolution than 4D flow MRI. TOF-MRA SIG and CFD WSS of the major cerebral arteries showed reasonable consensus with the locations where the WSS was relatively high. However, the visualizations were very different between TOF-MRA SIG and CFD WSS at the internal carotid artery bifurcations, the anterior cerebral arteries, and the anterior communicating arteries. 4D flow MRI, TOF-MRA SIG, and CFD are complementary methods that can provide additional insight into the hemodynamics of the human cerebral artery.

In-vitro and In-Vivo Assessment of 4D Flow MRI Reynolds Stress Mapping for Pulsatile Blood Flow.

Imaging hemodynamics play an important role in the diagnosis of abnormal blood flow due to vascular and valvular diseases as well as in monitoring the recovery of normal blood flow after surgical or interventional treatment. Recently, characterization of turbulent blood flow using 4D flow magnetic resonance imaging (MRI) has been demonstrated by utilizing the changes in signal magnitude depending on intravoxel spin distribution. The imaging sequence was extended with a six-directional icosahedral (ICOSA6) flow-encoding to characterize all elements of the Reynolds stress tensor (RST) in turbulent blood flow. In the present study, we aimed to demonstrate the feasibility of full RST analysis using ICOSA6 4D flow MRI under physiological conditions. First, the turbulence analysis was performed through in vitro experiments with a physiological pulsatile flow condition. Second, a total of 12 normal subjects and one patient with severe aortic stenosis were analyzed using the same sequence. The in-vitro study showed that total turbulent kinetic energy (TKE) was less affected by the signal-to-noise ratio (SNR), however, maximum principal turbulence shear stress (MPTSS) and total turbulence production (TP) had a noise-induced bias. Smaller degree of the bias was observed for TP compared to MPTSS. In-vivo study showed that the subject-variability on turbulence quantification was relatively low for the consistent scan protocol. The in vivo demonstration of the stenosis patient showed that the turbulence analysis could clearly distinguish the difference in all turbulence parameters as they were at least an order of magnitude larger than those from the normal subjects.

Measurement of red blood cell aggregation using X-ray phase contrast imaging.

When a coherent beam illuminates spatially disordered particles, speckle patterns are formed due to interference of the scattered light waves. Speckle patterns from biological tissues using synchrotron phase contrast X-ray imaging can provide functional information about micro-scale morphological structures of the tissues. In this study, we investigated the size and contrast variations of the speckles of aggregated red blood cells (RBCs) suspensions with varying the degree of RBC aggregation. Results show that the degree of RBC aggregation is a governing parameter on the change of speckle characteristics. This blood speckle analysis method can be used as a novel modality for monitoring RBC aggregation.

Extent of Subprosthetic Pannus after Aortic Valve Replacement: Changes Over Time and Relationship with Echocardiographic Findings.

Purpose: This study aimed to evaluate changes of subprosthetic pannus on cardiac CT and determine its relationship to echocardiographic findings in patients with mechanical aortic valve replacement (AVR). Materials and Methods: Between April 2011 and November 2017, 17 AVR patients (56.8 ± 8.9 years, 12% male) who showed pannus formation on CT and had undergone both follow-up CT and echocardiography were included. The mean interval from AVR to the date of pannus detection was 10.5 ± 7.1 years. In the initial and follow-up CT and echocardiography, the pannus extent and echocardiographic parameters were compared using paired t-tests. The relationship between the opening angle of the prosthetic valve and the pannus extent was evaluated using Pearson correlation analysis. Results: The pannus extent was significantly increased on CT (p < 0.05). The peak velocity (3.9 ± 0.8 m/s vs. 4.2 ± 0.8 m/s, p = 0.03) and mean pressure gradient (36.4 ± 15.5 mm Hg vs. 42.1 ± 15.8 mm Hg, p = 0.03) were significantly increased. The mean opening angles of the mechanical aortic leaflets were slightly decreased, but there was no statistical significance (73.1 ± 8.3° vs. 69.4 ± 12.1°, p = 0.12). The opening angle of the prosthetic leaflets was inversely correlated with the pannus extent (r = -0.57, p < 0.001). Conclusion: The pannus extent increases over time, increasing transvalvular peak velocity and the pressure gradient. CT can be used to evaluate the pannus extent associated with hemodynamic changes that need to be managed by surgical intervention.