Off-pump mitral valved stent implantation: comparison of apical and subannular fixation techniques

A large cohort of patients suffering from severe mitral regurgitation does not meet the indications for conventional surgery and would greatly benefit from a transcatheter approach in the beating heart. Consequently, off-pump transcatheter mitral valve procedures have been the focus of recent research. The aim of this study was the in vivo evaluation and comparison of subannular versus apical fixation of mitral valved stents to show the feasibility of subannular anchorage.

Twenty-two pigs received a self-expanding valved stent in the mitral position in an off-pump procedure. The first design (design AP: n = 12) was anchored apically and served as the control group. The second design (design SA: n = 10) included additional sub-annular fixation elements. Echocardiographic and haemodynamic evaluations were conducted before and 1 h after stent implantation.

Haemodynamic stability was achieved, and the capillary wedge pressure was within a normal range (AP: 11 ± 4 mmHg, SA: 9 ± 4 mmHg). Paravalvular leakages were trace or less in 19 of 20 cases. The mean gradients across the valved stent increased (P ≤ 0.014) but remained within a physiological range in both groups (AP: 1.2 ± 0.6 mmHg, SA: 2.6 ± 2.0 mmHg). The longitudinal heart function remained within a physiological normal range (AP: 0.95 ± 0.1 cm, SA: 0.95 ± 0.1 cm) but was reduced in group SA. The ejection fraction decreased after stent implantation (AP: 52 ± 10%, SA: 48 ± 4%). The mean survival time was higher in group AP compared with group SA.

The proof-of-principle for the subannular fixation was shown with haemodynamic stability, low gradients and physiological longitudinal function. A decreased ejection fraction, survival time and fractures identify potential areas for improvement. With regard to the long-term outcome, the group with subannular fixation did not reach the results of the group with apical fixation in this study.