Transcatheter mitral valve implantation: supra-annular and subvalvular fixation techniques

OBJECTIVES

Transcatheter mitral valved stent implantation provides an off-pump treatment option for mitral valve regurgitation, especially for secondary mitral valve regurgitation. The aim of this study was to evaluate novel fixation strategies: direct fixation (SUPRA) and subvalvular fixation (sub-VALV) to successfully implement alternative fixation methods at the mitral annulus and to reduce radial stent and apical tether forces.

METHODS

Specific concepts were developed for the supra-annular hook-shaped fixation (SUPRA) and the subvalvular fixation (sub-VALV). These prototypes were compared with the sole apical tether fixation (AP) methods. Thirty-three pigs underwent mitral valved stent implantation accompanied by standardized transoesophageal echocardiographic and haemodynamic evaluation of heart function and the stent performance 1 h after implantation. Additionally, animals were followed up for 3 months.

RESULTS

Secure deployment and correct positioning with low transvalvular gradients were achieved in all cases with mitral valved stent implantation. Nevertheless, 2 pigs died due to rhythm disturbances during dissection and pre-transcatheter mitral valve implantation. Paravalvular leakages were trace or less in prototypes with supra-annular fixation and sole apical fixation. In contrast, moderate paravalvular leakages were observed in the sub-VALV group (P < 0.001). In addition, the effect of a specific stent design on heart function was demonstrated: an increased rate of ischaemia and arrhythmia (P = 0.037) and a small left ventricular ejection fraction reduction (P < 0.05) were observed in the group with subvalvular fixation. In all but 1 case, gross evaluation demonstrated a good ingrowth of the valved stents of between 36% and 100% tissue coverage after a follow-up of 1 month or longer.

CONCLUSIONS

The low degree of paravalvular leakages in the supra-annular and apical fixation groups and the normal longitudinal function highlight the good alignment of these new mitral valved stent designs within the native anatomy. The novel, hook-shaped, supra-annular fixation elements were well tolerated in the hearts resulting in excellent health of the animals at long-term follow-up times of up to 3 months.

Transcatheter mitral valve implantation: a percutaneous transapical system

Objectives

Despite recent achievements, implantation of a transcatheter mitral valved stent remains challenging. In this study, we present a different approach for implantation of a percutaneous mitral valved stent.

Methods

Percutaneous transapical access is combined with, respectively, a left-transatrial, right-transatrial/transseptal or transfemoral/transseptal approach for mitral valve stent implantation and secure fixation. The apical fixation and occlusion are ensured with an Amplatzer occluder. This novel approach was tested in 22 porcine hearts in an in vitro setting under the guidance of fluoroscopy ( n  = 11) and endoscopy ( n  = 11). The in vitro setup included continuous flushing at 37 °C. We determined the feasibility, time of implantation, stent deployment and stent fixation.

Results

Percutaneous mitral valved stent implantation was successful in all cases. Good handling properties and precise positioning were achieved. Time of implantation was comparable in the fluoroscopic and endoscopic groups at 10:41 ± 3:18 and 10:09 ± 2:42 min, respectively. Apical fixation with the occluder was excellent in all 22 cases.

Conclusions

The feasibility of percutaneous mitral valved stent implantation has been demonstrated in preliminary in vitro experiments. Subsequent studies are warranted to determine the efficacy of this minimally invasive catheter-based mitral valved stent implantation.