Prediction of stenting related adverse events through patient-specific finite element modelling

Risk factors for in-stent restenosis in maintenance hemodialysis patients with central venous occlusive disease and biomechanical assessment of stents

OBJECTIVES

To investigate the risk factors and biomechanical mechanisms of in-stent restenosis (ISR) in central venous occlusive disease (CVOD).

PATIENTS AND METHODS

This retrospective study consecutively included 77 maintenance hemodialysis (MHD) patients with CVOD who received the first percutaneous transluminal angioplasty with stenting (PTS) due to symptomatic CVOD in a tertiary hospital. The mean age was 59.7 ± 14.0 years, and 51.9% of patients were male. The clinical characteristics, occurrence of ISR and patency rates were recorded. Finite element method was applied to assess the biomechanical properties of stents.

RESULTS

Among 77 patients with a mean CVS score of 8.0 ± 2.8, 20.8%, 62.3%, and 16.9% of patients had the main vein of CVOD in the subclavian vein, brachiocephalic vein, and superior vena cava, respectively. A total of 72 (93.5%) patients received successful PTS treatment, for which the stents implanted were mainly Fluency covered stent (48.6%) and SMART bare stent (31.9%). During 15 (10-24)-months of follow-up, ISR occurred in 36.1% of the 72 patients. The primary and assisted primary patency rates at 6, 12, and 18 months were 78%, 56%, 42% and 95%, 90%, 87%, respectively. A prolonged dialysis vintage was an independent risk factor for ISR, yet the stent type or the main vein location was not correlated with ISR. Among three laser-engraving stents, the SMART stent was the best in terms of flexibility, stress, and strain on stents but worst in stress or strain on vessels. The Luminexx stent was the best in radial force and worst in stress or strain on stents. The Vici stent was the best in stress and strain on vessels and worst in radial force and flexibility.

CONCLUSIONS

An unsatisfactory comprehensive biomechanical performance from configurations rooted in existing stents may account for the high incidence of ISR in CVOD.

Finite element modeling with patient-specific geometry to assess clinical risks of percutaneous pulmonary valve implantation

BACKGROUND

Percutaneous pulmonary valve implantation (PPVI) is a non-surgical treatment for right ventricular outflow tract (RVOT) dysfunction. During PPVI, a stented valve, delivered via catheter, replaces the dysfunctional pulmonary valve. Stent oversizing allows valve anchoring within the RVOT, but overexpansion can intrude on the surrounding structures. Potentially dangerous outcomes include aortic valve insufficiency (AVI) from aortic root (AR) distortion and myocardial ischemia from coronary artery (CA) compression. Currently, risks are evaluated via balloon angioplasty/sizing before stent deployment. Patient-specific finite element (FE) analysis frameworks can improve pre-procedural risk assessment, but current methods require hundreds of hours of high-performance computation.

METHODS

We created a simplified method to simulate the procedure using patient-specific FE models for accurate, efficient pre-procedural PPVI (using balloon expandable valves) risk assessment. The methodology was tested by retrospectively evaluating the clinical outcome of 12 PPVI candidates.

RESULTS

Of 12 patients (median age 14.5 years) with dysfunctional RVOT, 7 had native RVOT and 5 had RV-PA conduits. Seven patients had undergone successful RVOT stent/valve placement, three had significant AVI on balloon testing, one had left CA compression, and one had both AVI and left CA compression. A model-calculated change of more than 20% in lumen diameter of the AR or coronary arteries correctly predicted aortic valve sufficiency and/or CA compression in all the patients.

CONCLUSION

Agreement between FE results and clinical outcomes is excellent. Additionally, these models run in 2-6 min on a desktop computer, demonstrating potential use of FE analysis for pre-procedural risk assessment of PPVI in a clinically relevant timeframe.

A Modified Technique for Transcatheter Pulmonary Valve Implantation of SAPIEN 3 Valves in Large Right Ventricular Outflow Tract: A Matched Comparison Study

INTRODUCTION

Percutaneous pulmonary valve implantation (PPVI) with a SAPIEN 3 valve is effective for treating treat right ventricle outflow (RVOT) dysfunction. A modified technique was developed without prestenting using a protective valve delivery method. We aimed to compare the procedural results of the modified technique group (MTG) to those of patients in a conventional technique group (CTG).

METHODS

We designed a matched before-after study. All consecutive PPVI with SAPIEN 3 performed in the MTG over 9 months were matched, based on the RVOT type and size, to consecutive procedures performed previously with SAPIEN 3.

RESULTS

A total of 54 patients were included, equally distributed in the two groups. The sizes of the SAPIEN 3 valves were 23 mm (n = 9), 26 mm (n = 9), 29 mm (n = 36). The two groups were similar regarding demographic data, RVOT type, and pre-procedure hemodynamics. PPVI was performed in a single procedure in all patients of the MTG, whereas six (22.2%) patients of the CTG group underwent prestenting as a first step and valve implantation later (p = 0.02). The procedures were successful in all cases. Stent embolization was reported in two patients (7.4%) in the CTG, which were impacted in pulmonary arteries. In one case (3.7%), in the MTG, an unstable 29 mm SAPIEN 3 valve was stabilized with two stents and additional valve-in-valve implantation. The hemodynamics results were good in all cases, without significant differences between the two groups. The procedures' durations and fluoroscopy times were significantly reduced in the MTG (48.1 versus 82.6 min, p < 0.0001; 15.2 versus 29.8 min, p = 0.0002). During follow-up, neither stent fracture nor valve dysfunction was noticed in either group.

CONCLUSION

PPVI without prestenting and with a protective delivery method of the SAPIEN 3 valve significantly reduces the procedure's complexity, the duration, and the irradiation while maintaining excellent hemodynamics results in selected cases.

CMR and Percutaneous Treatment of Pulmonary Regurgitation: Outreach the Search for the Best Candidate

Performance of cardiovascular magnetic resonance (CMR) in the planning phase of percutaneous pulmonary valve implantation (PPVI) is needed for the accurate delineation of the right ventricular outflow tract (RVOT), coronary anatomy and the quantification of right ventricular (RV) volume overload in patients with significant pulmonary regurgitation (PR). This helps to find the correct timings for the intervention and prevention of PPVI-related complications such as coronary artery compression, device embolization and stent fractures. A defined CMR study protocol should be set for all PPVI candidates to reduce acquisition times and acquire essential sequences that are determinants for PPVI success. For correct RVOT sizing, contrast-free whole-heart sequences, preferably at end-systole, should be adopted in the pediatric population thanks to their high reproducibility and concordance with invasive angiographic data. When CMR is not feasible or contraindicated, cardiac computed tomography (CCT) may be performed for high-resolution cardiac imaging and eventually the acquisition of complementary functional data. The aim of this review is to underline the role of CMR and advanced multimodality imaging in the context of pre-procedural planning of PPVI concerning its current and potential future applications.

Numerical Assessment of the Risk of Abnormal Endothelialization for Diverter Devices: Clinical Data Driven Numerical Study

Numerical modeling is an effective tool for preoperative planning. The present work is devoted to a retrospective analysis of neurosurgical treatments for the occlusion of cerebral aneurysms using flow-diverters and hemodynamic factors affecting stent endothelization. Several different geometric approaches have been considered for virtual flow-diverters deployment. A comparative analysis of hemodynamic parameters as a result of computational modeling has been carried out basing on the four clinical cases: one successful treatment, one with no occlusion and two with in stent stenosis. For the first time, a quantitative assessment of both: the limiting magnitude of shear stresses that are necessary for the occurrence of in stent stenosis (MaxWSS > 1.23) and for conditions in which endothelialization is insufficiently active and occlusion of the cervical part of the aneurysm does not occur (MaxWSS < 1.68)—has been statistacally proven (p < 0.01).

Coronary Artery Anomalies and Their Impact on the Feasibility of Percutaneous Pulmonary Valve Implantation

One of the major obstacles preventing successful percutaneous pulmonary valve implantation (PPVI) is related to the close proximity of coronary artery branches to the expected landing zone. The aim of this study was to assess the frequency of coronary artery anomalies (CAAs) especially those associated with major coronary branches crossing the right ventricular outflow tract (RVOT) and to describe their relevance for the feasibility of percutaneous pulmonary valve implantation (PPVI). In our retrospective single-center study 90 patients were evaluated who underwent invasive testing for PPVI in our institution from 1/2010 to 1/2020. CAAs were identified in seven patients (8%) associated with major branches crossing the RVOT due to origin of the left anterior descending (LAD) or a single coronary artery from the right aortic sinus. In 5/7 patients with CAAs balloon testing of the RVOT and selective coronary angiographies revealed a sufficiently large landing zone distal to the coronary artery branch. While unfavorable RVOT dimensions prevented PPVI in one, PPVI was performed successfully in the remaining four patients. The relatively short landing zone required application of the "folded" melody technique in two patients. All patients are doing well (mean follow-up 3 years). CAAs associated with major coronary branches crossing the RVOT can be expected in about 8% of patients who are potential candidates for PPVI. Since the LAD crossed the RVOT below the plane of the pulmonary valve successful distal implantation of the valve was possible in 4/7 patients. Therefore these coronary anomalies should not be considered as primary contraindications for PPVI.

Renaissance of Cardiac Imaging to Assist Percutaneous Interventions in Congenital Heart Diseases:The Role of Three-Dimensional Echocardiography and Multimodality Imaging

Percutaneous interventions have completely refashioned the management of children with congenital heart diseases (CHD) and the use of non-invasive imaging has become the gold standard to plan and guide these procedures in the modern era. We are now facing a dual challenge to improve the standard of care in low-risk patients, and to shift our strategies from the classic open chest surgery to imaging-guided percutaneous interventions in high-risk patients. Such rapid evolution of ultrasound technologies over the last 20 years have permitted the integration of transthoracic, transesophageal and intracardiac echocardiography into the interventional workflow to improve image guidance and reduce radiation burden from fluoroscopy and angiography. Specifically, miniaturization of transesophageal probe and advances in three-dimensional (3D) imaging techniques have enabled real-time 3D image guidance during complex interventional procedure, In addition, multimodality and fusion imaging techniques harness the strengths of different modalities to enhance understanding of anatomical and spatial relationship between different structures, improving communication and coordination between interventionalists and imaging specialists. In this review, we aim to provide an overview of 3D imaging modalities and multimodal fusion in procedural planning and live guidance of percutaneous interventions. At the present times, 3D imaging can no longer be considered a luxury but a routine clinical tool to improve procedural success and patient outcomes.

Prediction of post-stenting biomechanics in coarcted aortas: A pilot finite element study

Endovascular stenting has recently become a standard treatment for native coarctation of the aorta (CoA) in children and young adults, given the efficacy in relieving vessel obstruction with a low incidence of adverse events. Yet, despite the short-term success of the technique, late hypertension remains an endemic risk. To assess the impact of the percutaneous procedure on the aortic wall biomechanics, we designed a novel finite element (FE) protocol for the simulation of endovascular stenting in three patient-specific CoA anatomies, developing a remeshing procedure that allows for coping with different CoA severities. Our FE protocol was able to yield numerical results on stent distortions and stresses, as well as on changes in aortic wall stresses and distensibility. These results were consistent with intraprocedural in-vivo evidences and with previous findings from the literature, and they suggest that our numerical approach could be used to understand the role of patient specific anatomical features (CoA severity and arch type) on the post-stenting aortic biomechanics. If soundly validated on a vast cohort of patients, our approach could support patient selection for the procedure.

Percutaneous Pulmonary Valve Implantation: Current Status and Future Perspectives

Patients with congenital heart disease (CHD) with right ventricle outflow tract (RVOT) dysfunction need sequential pulmonary valve replacements throughout their life in the majority of cases. Since their introduction in 2000, the number of percutaneous pulmonary valve implantations (PPVI) has grown and reached over 10,000 procedures worldwide. Overall, PPVI has been proven safe and effective, but some anatomical variations can limit procedural success. This review discusses the current status and future perspectives of the procedure.