Multidetector computed tomography sizing of bioprosthetic valves: guidelines for measurement and implications for valve-in-valve therapies

Computed Tomography-Derived 3D Modeling to Guide Sizing and Planning of Transcatheter Mitral Valve Interventions

A plethora of catheter-based strategies have been developed to treat mitral valve disease. Evolving 3-dimensional (3D) multidetector computed tomography (MDCT) technology can accurately reconstruct the mitral valve by means of 3-dimensional computational modeling (3DCM) to allow virtual implantation of catheter-based devices. 3D printing complements computational modeling and offers implanting physician teams the opportunity to evaluate devices in life-size replicas of patient-specific cardiac anatomy. MDCT-derived 3D computational and 3D-printed modeling provides unprecedented insights to facilitate hands-on procedural planning, device training, and retrospective procedural evaluation. This overview summarizes current concepts and provides insight into the application of MDCT-derived 3DCM and 3D printing for the planning of transcatheter mitral valve replacement and closure of paravalvular leaks. Additionally, future directions in the development of 3DCM will be discussed.

Left ventricular outflow obstruction predicts increase in systolic pressure gradients and blood residence time after transcatheter mitral valve replacement

Left ventricular outflow tract (LVOT) obstruction is a relatively common consequence of transcatheter mitral valve replacement (TMVR). Although LVOT obstruction is associated with heart failure and adverse remodelling, its effects upon left ventricular hemodynamics remain poorly characterised. This study uses validated computational models to identify the LVOT obstruction degree that causes significant changes in ventricular hemodynamics after TMVR. Seven TMVR patients underwent personalised flow simulations based on pre-procedural imaging data. Different virtual valve configurations were simulated in each case, for a total of 32 simulations, and the resulting obstruction degree was correlated with pressure gradients and flow residence times. These simulations identified a threshold LVOT obstruction degree of 35%, beyond which significant deterioration of systolic function was observed. The mean increase from baseline (pre-TMVR) in the peak systolic pressure gradient rose from 5.7% to 30.1% above this threshold value. The average blood volume staying inside the ventricle for more than two cycles also increased from 4.4% to 57.5% for obstruction degrees above 35%, while the flow entering and leaving the ventricle within one cycle decreased by 13.9%. These results demonstrate the unique ability of modelling to predict the hemodynamic consequences of TMVR and to assist in the clinical decision-making process.

Cardiac CT in prosthetic aortic valve complications

In the current era of transcatheter device therapy, the prevalence of prosthetic aortic valves and their associated complications is increasing. Echocardiography remains the first-line imaging investigation for the assessment of prosthetic valve complications, however, this often fails to identify the underlying mechanism of prosthesis failure. Recently, cardiac CT has emerged as an imaging technique capable of providing high isotropic spatial resolution of the prosthetic valve and its utility can provide important complementary diagnostic information. In this pictorial review, we present a series of common prosthetic aortic valve complications imaged with cardiac CT and demonstrate how use of this modality can enhance diagnostic accuracy.

The Lnc RNA SPRY4-IT1 Modulates Trophoblast Cell Invasion and Migration by Affecting the Epithelial-Mesenchymal Transition

Preeclampsia is a common, pregnancy-specific disease and a major contributor to maternal and foetal morbidity and mortality. Some placental abnormalities, including deficient implantation, abnormal trophoblast cell function, and improper placental vascular development, are believed to lead to preeclampsia. The long noncoding RNA SPRY4-IT1 is more highly expressed in preeclamptic human placentas than in normal placentas. We assessed the role of epithelial-mesenchymal transition (EMT)-associated invasion and migration in HTR-8/SVneo trophoblast cells. Overexpression of SPRY4-IT1 suppressed trophoblast cell migration and invasion, whereas reduced expression of SPRY4-IT1 prevented the EMT process. Mechanistically, an RNA immunoprecipitation experiment showed that SPRY4-IT1 bound directly to HuR and mediated the β-catenin expression associated with EMT in HTR-8/SVneo cells. Moreover, the expression levels of genes in the WNT family, such as WNT3 and WNT5B, were changed after transfection of HTR-8/SVneo with SPRY4-IT1. Together, our results highlight the roles of SPRY4-IT1 in causing trophoblast cell dysfunction by acting through the Wnt/β-catenin pathway, and consequently in impairing spiral artery remodelling. These results suggest a new potential therapeutic target for intervention against preeclampsia.

Complementary role of cardiac CT in the assessment of aortic valve replacement dysfunction

Aortic valve replacement is the second most common cardiothoracic procedure in the UK. With an ageing population, there are an increasing number of patients with prosthetic valves that require follow-up. Imaging of prosthetic valves is challenging with conventional echocardiographic techniques making early detection of valve dysfunction or complications difficult. CT has recently emerged as a complementary approach offering excellent spatial resolution and the ability to identify a range of aortic valve replacement complications including structural valve dysfunction, thrombus development, pannus formation and prosthetic valve infective endocarditis. This review discusses each and how CT might be incorporated into a multimodal cardiovascular imaging pathway for the assessment of aortic valve replacements and in guiding clinical management.

Computer-Assisted Transcatheter Heart Valve Implantation in Valve-in-Valve Procedures

Objective

Valve-in-valve (ViV) procedures are increasingly being considered as an alternative to redo surgery for the treatment of degenerated bioprosthetic heart valves in patients with excessive reoperative risk. The objective of our study was to evaluate the feasibility of computer guidance in transcatheter heart valve (THV) implantation during ViV procedures.

Methods

Preprocedural electrocardiogram-gated computed tomography–scan images were processed using semiautomatic segmentation of the degenerated bioprosthesis’ radiopaque landmarks and of the ascending aorta. Virtual three-dimensional (3D) reconstructions were created. A virtual plane was subsequently added to the 3D reconstructions, indicating the optimal landing plane of the THV inside the tissue valve. Within a hybrid operating theater, a 3D/2D registration was used to superimpose the 3D reconstructions, while dynamic tracking was allowed to maintain the superimposition onto the fluoroscopic images. The THV was afterward implanted according to the optimal landing plane. Projection of the ascending aorta and the coronary arteries was used to assess the risk of coronary ostia obstruction.

Results

Between January 2014 and October 2014, nine patients underwent aortic ViV procedures in our institution. Among those nine patients, five procedures were retrospectively evaluated as a validation step using the proposed method. The mean (SD) superimposition error was 1.1 (0.75) mm. Subsequently, two live cases were prospectively carried out using our approach, successfully implanting the THV inside the degenerated tissue valve.

Conclusions

Our study demonstrates the feasibility of a computer-guided implantation of THV in ViV procedures. Moreover, it suggests that augmented reality may increase the reliability of THV implantation inside degenerated bioprostheses through better reproducibility.