Efficient blood flow simulations for the design of stented valve reducer in enlarged ventricular outflow tracts

Tetralogy of Fallot is a congenital heart disease characterized over time, after the initial repair, by the absence of a functioning pulmonary valve, which causes regurgitation, and by progressive enlargement of the right ventricle and pulmonary arteries. Due to this pathological anatomy, available transcatheter valves are usually too small to be deployed in the enlarged right ventricular outflow tracts (RVOT). To avoid surgical valve replacement, an alternative consists in implanting a reducer prior to or in combination with a transcatheter valve. We describe a computational model to study the effect of a stented valve RVOT reducer on the hemodynamics in enlarged ventricular outflow tracts. To this aim, blood flow in the right ventricular outflow tract is modeled via the incompressible Navier--Stokes equations coupled to a simplified valve model, numerically solved with a standard finite element method and with a reduced order model based on Proper Orthogonal Decomposition (POD). Numerical simulations are based on a patient geometry obtained from medical imaging and boundary conditions tuned according to measurements of inlet flow rates and pressures. Different geometrical models of the reducer are built, varying its length and/or diameter, and compared with the initial device-free state. Simulations thus investigate multiple device configurations and describe the effect of geometry on hemodynamics. Forces exerted on the valve and on the reducer are monitored, varying with geometrical parameters. Results support the thesis that the reducer does not introduce significant pressure gradients, as was found in animal experiments. Finally, we demonstrate how computational complexity can be reduced with POD

316 Percutaneous right outflow tract valve implantation: when should we pre-stent?

IntroductionPercutaneous pulmonary valve insertion has been recently introduced in clinical setting. Patient selection is widely accepted. Initial results demonstrated early and differed stent fractures that make consider pre-stenting as a previous step for the procedure. To date, differed or intra-procedure pre-stenting are both accepted techniques.Patients and methodsWe reviewed patients included over the last 6 months in the prospective study (REVALV) for patients undergoing RVOT intervention for severe stenosis and/or insufficiency. Only valved stent group is analyzed here. All patients undergoing valved stent implantation are previously pre-stented with a bare metal stent according to present recommendations. Thirty-seven patients were included, distributed in two gropus according moment of pre-stenting: differed pre-stenting (bare metal stent implantation several days before valved stent implantation -20 patients-) and same procedure pre-stenting (bare metal stent implantation at the same procedure of valved stent implantation-17 patients-). For analytical purposes, we considered RVOT anatomy (homograft, synthetic tube, patch-extended RVOT or native outflow tract).ResultsOverall, no differences were found regarding mean procedure times (77,35 vs 96,88, p=NS) and time of hospitalization (2,95 vs 3,63, p=NS). Mean delay time from pre-stenting to valvulation was 196,5 + −68 days. Rv to Ao ratio improvement from basal to valvulation was significantly better in intra-procedure pre-stenting group (0,172 vs 0,373, p=0,009). Concerning complications, bare metal stent mobilization happened just after implantation while trying to place valved stent delivery gain. Two pelvic hematomas were observed (one of each group).ConclusionsIntra-procedure pre-stenting influences final result when considering RV-to-Ao ratio improvement, probably related to increase radial strength. The risk, however, remains higher as freshly implanted bare metal stent can mobilize, especially in native RVOT. Stratification of patient should be considered while choosing candidates for valved stent implantation

286 – Percutaneous right outflow tract valve implantation: substrate matters

IntroductionPercutaneous pulmonary valve insertion has been recently introduced in clinical setting. Patient selection is widely accepted. These candidates are however heterogeneous, in regard of heart defects, and type of surgical right ventricular outflow tract (RVOT) reconstruction. It is presently unclear in the literature if type of surgical reconstruction matters for the success of the pulmonary valve insertion. Our goal was to compare the hemodynamic results of percutaneous pulmonary valve in patients with homografts, prosthetic conduit or RVOT reconstructed with patch.Patients and methodsWe reviewed patients included over the last 6 months in the prospective study (REVALV) for patients undergoing RVOT intervention for severe stenosis and/or insufficiency. Only valved stent group is analyzed here. All patients undergoing valved stent implantation are previously pre-stented with a bare metal stent according to present recommendations. Thirty-seven patients were included, distributed in three groups according to type of RVOT reconstruction (homograft REVALV is a multicentric prospective study for patients undergoing RVOT intervention for severe stenosis and/or insufficiency. Patients are distributed in three groups according to type of RVOT reconstruction (homograft, n = 10; prosthetic conduit, n = 20; RVOT enlargement by patch, n = 7).ResultsOverall, all groups were similar in RV to AP gradient improvement (after pre-stenting mean 30,79 vs 28 p = NS; final result mean 23,71 vs 28,17, p = NS), RV to aorta pressures ratio (after pre-stenting 0,187 vs 0,3117 p = NS; final result man 0,315 vs 0,317, p = NS). If considering non-extensible synthetic tubes we observe that RV-to-AP improvement is significantly worst to the rest of the group (mean 7,07 vs 0,17, p = 0,005). When focusing on outflow tract diameter, results did not differ in homograft group and patch group. In contrast, diameter did play a role in those patients having a synthetic tube, with a cut-off at 20mm diameter. Below 20mm, relieve of outflow tract gradient was significantly worse than for bigger conduits.DiscussionPulmonary valve insertion is efficient in all type of RVOT reconstruction at least in the short term. The diameter of the conduits did not play a role in RVOT obstruction relief as long as surgical substrates are homografts or patch enlargement. In patients with prosthetic conduits, size matters. In non-extensible synthetic tubes results are worst. Reduced distensibility and progressive diameter reduction may lead to not consider these patients as good candidates for this procedure

Simultaneous pressure-volume measurements using optical sensors and MRI 1 for left ventricle function assessment during animal experiment 2

International audienceSimultaneous pressure and volume measurements enable the extraction of valuable parameters for left ventricle function assessment. Cardiac MR has proven to be the most accurate method for volume estimation. Nonetheless, measuring pressure simultaneously during MRI acquisitions remains a challenge given the magnetic nature of the widely used pressure transducers. In this study we show the feasibility of simultaneous in vivo pressure-volume acquisitions with MRI using optical pressure sensors. Pressure-volume loops were calculated while inducing three inotropic states in a sheep and functional indices were extracted, using single beat loops, to characterize systolic and diastolic performance. Functional indices evolved as expected in response to positive inotropic stimuli. The end-systolic elastance, representing the contractility index, the diastolic myocardium compliance, and the cardiac work efficiency all increased when inducing inotropic state enhancement. The association of MRI and optical pressure sensors within the left ventricle successfully enabled pressure-volume loop analysis after having respective data simultaneously recorded during the experimentation without the need to move the animal between each inotropic state

275: Percutaneous insertion of a Melody valve in tricuspid position: technical aspects

Backgroundpercutaneous transcatheter heart valve replacement of aortic or pulmonary valve is established. Transcatheter atrioventricular valve replacement is been described. We report our experience focusing on the technical aspects.Methodswe retrospectively review the files of patients who received a transcatheter valve in tricuspid position between 2008 and 2012.ResultsFour patients were found. 3 had a heterograft (conduit of 14-mm, Sorin 33 et Edwards Perimount 33) and one had a connection between the RA and the RV infundibulum without a valve. Two patients had tricuspid regurgitation as a primary lesion, one had stenotic valve and the last one a mixted lesion. All successfully received a Melody valve from a femoral access. In patients with stenotic lesion, a predilatation using a high pressure balloon was performed before valve implant. In patients with regurgitation, the landing zone was calibrated using a low pressure balloon. These patients were presented to create a landing zone of adequate diameter. Melody valves were inserted using a 22-mm balloon catheter in 3 and a 24-mm in one. All but one were post-dilated. There was no significant regurgitation. The mean gradient across the tricuspid valve felt from 12 to 4.6-mmHg. One patient needed an epicardic pacemaker because of AV block following balloon dilatation. One patient required inotropic support and ventilation following the procedure but recovered after few days.ConclusionTranscatheter tricuspid valve insertion is feasible in patients with surgical hetero or homografts after a careful selection. The mechanism of dysfunction must be known. In case of stenosis or mixted lesions, the only question is to know if the stenosis could be relief. In case of regurgitation, it is very important to know the features of surgical substrats and to calibrate the tricuspid orifice. Finally, patients with inappropriate landing zone should be presented prior to valve insertion

Transcatheter tricuspid valve implantation: A multicentre French study

SummaryBackgroundTranscatheter valve-in-valve (VIV) implantation in failing bioprosthesis is an emerging field in cardiology.AimTo report on a French multicentre experience and a literature review of tricuspid VIV implantation.MethodsWe approached different institutions and collected 10 unpublished cases; a literature review identified 71 patients, including our 10 cases. Clinical aspects and haemodynamic data are discussed.ResultsAmong our 10 unpublished cases, the reason for implantation was significant tricuspid stenosis (n=4), significant tricuspid regurgitation (n=1) or mixed lesion (n=5). Implantation was performed under general anaesthesia at mean age 28±17 years. The 22mm Melody valve was implanted in seven patients; the Edwards SAPIEN valve was implanted in three patients. The procedure succeeded in all cases, despite two embolizations in the right cardiac chambers; in both cases, the valve was stabilized close to the tricuspid annulus using a self-expandable stent, before implantation of a second Edwards SAPIEN valve. Functional class improved in all but one case. Mean diastolic gradient decreased from 9±2.45mmHg to 3.65±0.7mmHg (p=0.007); no more than trivial regurgitation was noticed. Among the published cases, the Melody valve was implanted in 41 patients, the Edwards SAPIEN valve in 29 patients and the Braile valve in one patient. Short-term results were similar for our 10 cases, but mid-term results are not yet available.ConclusionsTricuspid VIV implantation using the Melody or Edwards SAPIEN valves is a feasible and effective procedure for selected patients with failing bioprosthesis

Atlas-Based Reduced Models of Blood Flows for Fast Patient-Specific Simulations

The original publication is available at www.springerlink.com.International audienceModel-based interpretation of the complex clinical data now available (shape, motion, flow) can provide quantitative information for diagnosis as well as predictions. However such models can be extremely time consuming, which does not always fit with the clinical time constraints. The aim of this work is to propose a model reduction technique to perform faster patient-specific simulations with prior knowledge built from simulations on an average anatomy. Rather than simulating a full fluid problem on individual patients, we create a representative `template' of the artery shape. A full flow simulation is carried out only on this template, and a reduced model is built from the results. Then this reduced model can be transported to the individual geometries, allowing faster computational analysis. % Here we propose a preliminary validation of this idea. A well-posed framework based on currents representation of shapes is used to create an unbiased template of the pulmonary artery for 4 patients with Tetralogy of Fallot. Then, a reduced computational fluid dynamics model is built on this template. Finally, we demonstrate that this reduced model can represent a specific patient simulation

Off-pump replacement of the pulmonary valve in large right ventricular outflow tracts: A hybrid approach

BackgroundPercutaneous pulmonary valve replacement has recently been introduced and is under investigation in humans. This technique is, however, limited to patients with a right ventricular outflow tract that does not exceed 22 mm in diameter. We report our experience of off-pump pulmonary valve replacement using a hybrid approach in animals with large right ventricular outflow tracts.MethodsEight ewes were included in the protocol and were equally divided into 2 groups. A left thoracotomy was first performed, and the main pulmonary artery was banded by using 2 radiopaque rings with a diameter of 18 mm that allowed for further pulmonary valve replacement. We then intended to implant a valved stent either percutaneously (group 1) or through a transventricular approach (group 2). All animals were killed after valve implantation. The operation allowed the pulmonary diameter to be reduced from 30 to 17.6 mm.ResultsThe right ventricular pressure did not significantly increase after reduction of the pulmonary artery diameter (25 vs 36 mm Hg). Subsequent pulmonary valve replacement through a percutaneous or a transventricular approach was always possible without any requirement for extracorporeal circulation. All devices were successfully delivered inside the pulmonary artery banding and were functioning perfectly at early evaluation.ConclusionsImplantation of a pulmonary valve is possible in ewes through a hybrid approach when the right ventricular outflow tract exceeds 22 mm in diameter. This involves both surgeons and interventionists and allows for a staged procedure in which the valvulation is performed percutaneously or, for a combined hybrid approach, in which the valve is implanted off pump transventricularly during the same operation

Transcatheter valve implantation for right atrium‐to‐right ventricle conduit obstruction or regurgitation after modified Björk–fontan procedure

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136276/1/ccd26648_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136276/2/ccd26648.pd