Off-pump mitral valved stent implantation: A 3D-transesophageal echocardiographic based comparison of apical and sub-annular fixation techniques

Objectives: In this study a comparison of two different designs for off-pump mitral valved stent implantation in the beating heart is presented to conduct a proof of concept for a sub-annular fixation technique.

Methods: 16 pigs received a self-expanding valved stent in the mitral position via a transapical approach in the beating heart. The stents were comprised of an atrial element, a tubular ventricular body accommodating a bioprosthetic heart valve and an apical fixation system. The ventricular body was modified in order to evaluate the influence of a sub-annular fixation technique: In the first design A (n = 8), the ventricular body was shaped cylindrical. In the second design B (n = 8) additional sub-annular fixation elements were included in the stent body. A 2D and 3D transesophageal echocardiographic (TEE) and a hemodynamic evaluation following standardized protocols were conducted pre- (n = 16) and post implantation (n = 16).

Results: All stents were successfully deployed and positioned under sole TEE guidance. No persisting arrhythmia (e.g. atrial fibrillation) during the acute follow up was observed in three (A: n = 1; B: n = 2) and hemodynamic stability in the remaining cases.

3D TEE proved well suited to evaluate paravalvular leakages (PVL) showing trace or less PVL in all but one case. Evaluation of the TEE parameters (Table 1) showed a slightly decreasing EF (p ≤ 0.043), remaining within a physiological range in group A. Changes of E/A and E/E´ indicate a slightly reduced diastolic function in group B (p ≤ 0.028). An inter-group comparison showed a lower EF and E/A in group B compared to group A with sole apical fixation (p = 0.048; p = 0.003). Mean gradients across the mitral valve and valved stents were low.

Conclusion: Secure deployment and correct position of the valved stents was reproducibly achieved with both designs. Low gradients and a normal longitudinal function were achieved and a proof of principle was conducted for the sub-annular fixation technique. However, a slightly decreased diastolic function and EF in the group with sub-annular fixation is indicated and a potential for improvement (e.g. sizing of fixation elements) has been identified.

Echocardiographic comparison

		EF [%]	TEI Index [ ]	MAPSE [cm]	Pmean MV [mmHg]	E/A [ ]	E/E' []	LVOT obstr. [%]
EF: left ventricular ejection fraction; TEI Index: myocardial performance index; MAPSE: mitral annular plane systolic excursion, E/A: ratio of peak mitral flow velocities, E/E': left ventricular filling index; LVOT obstr.: obstruction of the left ventricular outflow tract; *: p < 0.05 indicating a statistical significant difference between group A and B (Mann-Whitney-U-Test); +: p < 0.05 indicating a statistical significant difference between pre- and post-implantation evaluation (Wilcoxon test)
Design Design A (n = 8) (n = 8)	Pre	64 ±  3	0.28 ±  0.07	1.2 ±  0.1	0.5 ±  0.4	1.2 ± 0.3	8.9 ± 2.6	−
Design A (n = 8)	Post	55 ± 7*+	0.37 ± 0.19	1.0 ± 0.1+	0.9 ± 0.6	1.2 ± 0.2*	13.1 ± 3.6+	14 ± 16
Design B (n = 8)	Pre	64 ± 5	0.35 ± 0.11	1.1 ± 0.1	0.4 ± 0.5	1.7 ± 0.5	9.0 ± 2.3	−
Design B (n = 8)	Post	47 ± 5*+	0.31 ± 0.14	0.9 ± 0.2+	2.7 ± 2.1	0.9 ± 0.1*+	17.2 ± 6.1+	9 ± 12