Transcatheter heart valve migration and embolization: rare and preventable?

This editorial refers to ‘Incidence and outcome of peri-procedural transcatheter heart valve embolization and migration: the TRAVEL registry (TranscatheteR HeArt Valve EmboLization and Migration)’†, by W.-K. Kim et al., on page 3156. Transcatheter heart valves (THVs) are deployed by frame expansion and anchored by the friction between the collapsible frame and the surrounding tissue. When THVs are found in the wrong place, the causes include initial malpositioning, migration, embolization, or combinations of these. Malpositioning is the deployment of a THV in an unfavourable position. Migration is the displacement of a THV within minutes, hours, or days after implantation. Embolization of a THV implies loss of permanent contact with the native valve structures. Embolizations of THVs have been observed since the early transcatheter aortic valve implantation (TAVI) experiences.1–3 The consequences of THV migration and embolization vary considerably.4 Some may go unnoticed by the patient (e.g. embolization with stable anchoring in the descending aorta and placement of a new prosthesis in the correct position) and some may have detrimental effects (e.g. obstruction of flow to vital organs necessitating emergency surgery).5 As THV embolizations occur infrequently, the causes, effects, and preventive measures are not well defined.6 , 7 Furthermore, the impact of rare phenomena may be underappreciated in randomized controlled trials due to restrictive inclusion criteria, limited cohort sizes, and highly selected centres and operators. Therefore, post-marketing surveillance programmes, real-world registries, and multicentre research collaborations are important to detect and characterize rare device effects. In the current issue of the European Heart Journal, Kim et al.8 report the results of a multicentre collaboration, which elucidates the incidence, causes, and outcomes of THV embolization and migration (TVEM). The authors have to be congratulated for their efforts to gather together data from 26 centres, which participated in this retrospective, international registry (Transcatheter Heart Valve Embolization and Migration: TRAVEL). A total of 29 636 TAVI procedures were analysed, and TVEM was found in 273 patients (0.92%). About one in five THVs moved to the left ventricle, while the majority migrated or embolized to the ascending aorta. Most cases were managed by implantation of another THV, but one in five TVEM patients were converted to open-heart surgery. Mortality was high in patients who required emergent cardiopulmonary support. In a propensity score analysis, TVEM was associated with a four-fold higher mortality and three-fold higher stroke rate at 30 days. Independent predictors for TVEM were the use of self-expanding or first-generation prostheses, and the presence of a bicuspid aortic valve. While in the early randomized TAVI trials THV embolization occurred at a rate of ∼0.5–1%,9–11 in the latest randomized controlled trial—comparing TAVI with a balloon-expandable THV with surgical aortic valve replacement in low surgical risk patients—TVEM did not occur in any of the 503 patients assigned to TAVI.12 While in the latter trial one patient (0.2%) required a second THV,12 in the latest randomized trial comparing TAVI with a self-expanding THV with surgical aortic valve replacement in low surgical risk patients, a second THV was implanted in 1.2% of patients.13 That the use of early-generation prostheses was a predictor for TVEM may be explained by an operator learning curve or improvements of THVs and delivery systems. The overall TVEM rate in the publication includes data of early TAVI experiences with first-generation devices implanted almost a decade ago and may therefore not be representative of outcomes with current systems. The reasons for TVEM are heterogenous (Figure 1). In half of patients, malpositioning led to TVEM, while manipulation, post-dilation, sizing errors, and fast-rate pacing failures were other leading causes. While most TVEM causes were technical issues during implantation, an important patient factor was an independent predictor for TEVM: the presence of a bicuspid aortic valve (BAV). There are only observational data on the performance of TAVI in BAV compared with TAVI in tricuspid aortic valves, because BAV patients were excluded from randomized controlled trials. Recently, the analysis of 2691 BAV patients undergoing TAVI showed a higher conversion rate to open-heart surgery for BAV patients (0.9% vs. 0.4 %, P = 0.03) and the need for a second valve was approximately doubled in BAV patients (0.4% vs. 0.2%, P = 0.16; R. Makkar, American College of Cardiology Annual Scientific Session 2019). Given the gradual expansion of TAVI to lower risk and younger patients, the prevalence, inherent risks, and anatomical peculiarities of BAV have to be respected and investigated in future randomized trials. Causes and treatments for transcatheter heart valve malpositioning, migration, and embolization. The authors considered one in three TVEMs preventable based on subjective criteria. Were all other TVEMs really inevitable? It is unlikely that an appropriately sized THV deployed in the correct position migrates or embolizes provided there is enough calcification in the aortic valve apparatus as outer support. Meticulous pre-procedural planning with correct measurement of the aortic annulus by multidetector computed tomography as a gold standard, selection of the most appropriate prosthesis type and size for the individual patient, accurate deployment techniques, assurance of adequate temporary pacing, and proper closed-loop communication between operators, assistants, and technicians make TVEM a rare scenario. Bail-out strategies for TVEM are chosen based on treatment urgency (haemodynamic compromise or obstruction of blood flow to the heart or the brain) and the location of the prosthesis (Figure 1). When THVs embolize into the left ventricle, removal of the device is mostly performed by open-heart surgery; however, conservative management by advancing a balloon over the wire and pulling the THV up into the aorta has also been accomplished. Most THV embolizations occur into the ascending aorta and can be managed percutaneously. An embolized THV in the ascending aorta should be percutaneously pulled to an area where the lumen of the aorta equals the diameter of the THV outflow and a stable position without obstruction of important aortic side branches is assured. The analysis of TVEM bail-out strategies showed that aggressive manipulation (pulling large devices beyond the aortic arch) should be avoided because of the risk of aortic dissection. While self-expanding THVs usually require snares for repositioning, embolized balloon-expandable THVs are mostly manipulated with balloons. Embolized THVs, that were finally seated proximal to the brain-supplying vessels, were not associated with an increased risk of stroke compared with embolized THVs distal to the left subclavian artery, albeit overall stroke rates were higher in TVEM compared with non-TVEM patients. Implantation of a second THV avoiding the errors of the first attempt was successful in the vast majority of patients and should be the first-line treatment strategy. Experience in TVEM management should be a prerequisite for teams performing TAVI. Access to cardiothoracic surgery and availability of percutaneous material for THV retrieval are mandatory. Besides proper TAVI planning, training, and deployment techniques, the advancements in delivery systems may further decrease the risk of TVEM. Future generations of self-expanding and mechanically expanding THVs are expected to allow retrieval options that are still applicable once the prosthesis is fully deployed. However, due to the inherent nature of THV interaction with the native valve apparatus and the lack of suture-based anchoring, the risk of TVEM will remain part of the TAVI procedure. Conflict of interest: R.K.B. is proctor for Boston Scientific, consultant for Edwards Lifesciences, and received grants from Abbott and Medtronic. J.G.W. is consultant for and has received research support from Edwards Lifesciences, Abbott, Boston Scientific, and Vivitro Labs. The opinions expressed in this article are not necessarily those of the Editors of the European Heart Journal or of the European Society of Cardiology.