Feasibility of a MPR‐based 3DTEE guidance protocol for transcatheter direct mitral valve annuloplasty

Several interventional approaches have been established for the treatment of severe mitral regurgitation (MR) in patients at elevated risk for surgery. Direct annuloplasty is a relatively novel option in transcatheter mitral valve repair dedicated to reverse pathology in specific subsets of MR. With regard to echocardiographic guidance, this procedure presents with higher efforts in comparison with edge‐to‐edge therapy to enable safe and exact positioning of the device's anchors; evidence on optimal peri‐interventional imaging is sparse. We tested a specific 3D‐echo‐guidance protocol implementing single‐beat multiplanar reconstruction (MPR) and evaluated its feasibility.


| INTRODUC TI ON
Mitral valve regurgitation (MR) is a common valvular disorder with an age-dependent prevalence of over 10% in the elder population beyond 75 years in industrialized countries. 1 With respect to its pathomechanism, functional or secondary MR (FMR), caused by a pathologic annular deformation, has to be discriminated from degenerative or primary MR (DMR) due to a leaflet pathology. In this context, it is well known that FMR is an independent predictor for a limited prognosis in concomitant heart failure. 2 6,7 While recommendations regarding echocardiographic imaging for percutaneous edge-to-edge repair are accepted and well-established (eg, 8,9 ), evidence and recommendations on optimal guidance for direct transcatheter annuloplasty are widely lacking. We developed a specific echocardiographic protocol, inheriting real time multiplanar reconstruction (MPR) for 3DTEE allowing optimal visualization of the anchoring points (for details, see Ref. 10). In this monocentric analysis, we aimed to investigate the feasibility of this echo protocol for guidance of direct annuloplasty procedures and discuss potential benefits and challenges in comparison with "conventional" modes of 3DTEE visualization.

| Ethical aspect
Since the study involved an anonymized, retrospective analysis of diagnostic standard data, ethics approval was not required according to German law.

| Statistical analysis
Statistical analysis was conducted using SPSS software version 23 (SPSS Inc). Continuous variables are presented as mean (±standard deviation) or as median values (with interquartile range); categorical variables are expressed as percentages. Continuous variables, in which normal distribution was confirmed with the modified Kolmogorov-Smirnov test, were compared using Student's t test or in variables, in which normal distribution was denied, the Wilcoxon-Whitney U test was used for comparison. Categorical variables were tested with Fisher's exact or chi-square test, as appropriate. Only P-values <.05 were considered to be statistically significant.

| Patients' baseline characteristics
Overall, sixteen patients (44% females) consecutively treated with transcatheter direct annuloplasty at the Heart Center University Medical Center Mainz until September 2017 were included in the present analysis. Leading etiology of MR was FMR (87.5%); additionally-and after approval of eligibility by the manufacturing company-one patient with a degenerative and one with a mixed pathomechanism were also included in the study. Median age at implantation was 79.6 years (IQR 58-86), and all patients were assessed to be at elevated risk for valve surgery (mean logistic Euroscore 22.0 ± 13.4%); further baseline characteristics are shown in Table 1.
All patients received Cardioband® devices of sizes C to F, each of these fixated by 15 anchors in mean; one patient with a mixed and one with a functional pathomechanism were primarily treated by a combined therapy approach including an interventional edge-toedge repair (both Abbott MitraClip®).  Guidance of each kind of TMVR is performed by a combination of fluoroscopic and echocardiographic imaging, usually performed using real time 3D modalities ( Figure 5). Echocardiography enables the real time visualization of tissue structures and is considered to have at least the same relevance as fluoroscopy during interventional procedures. 13 Optimal positioning and safe deployment of the device is the crucial step to achieve technical and procedural success for each kind of TMVR. While a distinct screening protocol has been elaborated by the manufacturing company, evidence as well as recommendations on optimal peri-interventional echocardiographic visualization and guidance for transcatheter direct annuloplasty is still lacking.  Yet, technically advanced procedures like transcatheter direct annuloplasty have different needs on TEE guidance, and here, "fixed" planes often do not entail true axis visualization with respect to the more "peripheral" structures like those situated around the mitral annulus. By MPR-based imaging as augmentation to "conventional" 3DTEE, anatomically correct visualization of the mitral annulus, mitral leaflets, and the delivery catheter is possible in order to assure perpendicularity and optimal tissue contact before starting anchoring (Figures 1 and 2 15,16 ). Nevertheless, implementation of MPR in 3DTEE might be the key to optimal true axis visualization of soft tissue structures in the context of these contemporary developments.

| Real time 3D MPR as augmentation of "conventional" 3DTEE-challenges and advantages in comparison with "conventional" echo guidance of TMVR
Thus, we think a profound knowledge of MRP-augmented imaging enhances the spectrum of advanced peri-interventional imaging tools to enable maximum accuracy and safety in centers offering all available forms of transcatheter therapies.

| Results of our monocentric experience with transcatheter direct annuloplasty inheriting advanced echocardiographic guiding with MPR
Showing a relevant reduction of MR by the device, the results of our initial implantation experience are similar to those of the feasibility trial. 4 We observed a large reduction of procedure times employing the MRP echocardiographic modality starting from up to four hours to under two hours; mean procedure time was even shorter (140 ± 55 minutes) in our study than in the feasibility trial

| Limitations
The present study has several limitations, caused by its retrospec-

| CON CLUS IONS
Multiplanar reconstruction has become available as additional feature on most recent TEE scanners. We demonstrated the feasibility and safety of the routine use of a real time MRP-based 3DTEE protocol for transcatheter direct annuloplasty and observed a substantial and continuous reduction in procedure time. As the variety of interventional devices dedicated to interventional valve repair or replacement is expected to increase, we propose that MPR-based echocardiography protocols will represent an important milestone to facilitate safe implantations for advanced procedures.

ACK N OWLED G M ENTS
Thomas Münzel is PI of the DZHK (German Center for Cardiovascular Research), Partner Site Rhine-Main, Mainz, Germany. The authors are responsible for the contents of this publication. We thank Margot Neuser for the support in realization of graphic illustration of the results.

CO N FLI C T O F I NTE R E S T S
Felix Kreidel reports having received consultancy and lecture honoraria from Abbott, Cardiac Implants, and Edwards Lifesciences.
Andres Beiras-Fernandez reports having received lecture honoraria from Edwards and consultancy from Abbott and NeoChord.