Trans-atrial Mitral Valve-in-valve Implantation: Experimental Feasibility Study In A Short-term Survival Porcine Model
Thang Duc Vu, Duc Viet Nguyen, Min Zin Oo, Ervin Marquez Ocampo, Hannah Qi-Hui Tan, Rachel En-Hui Cheong, Mohamed Alaa, Maria Tsopanomichalou Gklotsou, Lian Kah Ti, Theodoros Kofidis.
National University of Singapore, Singapore, Singapore.
Background: A plethora of recent research databases are focused on MV transcatheter interventions for large proportions of patients with degenerated bioprothesis who cannot tolerate re-do MV surgery (MVR), yet large-scale applications are still infrequent. Taking the step to specified pre-clinical studies is opt to master complex techniques, to overcome challenges, and to avoid complications. Therefore, this study aimed to assess the feasibility of transcatheter implantation a balloon-expandable valve within a bioprothesis in the mitral position via left atrial low-pressure access as a valve-in-valve (MVIV) technique. We hypothesize that using the trans-atrial approach to deploy the MVIV is robustly efficient and safe.Methods: Conventional on-pump MVR with cardiac arrest initially performed via median sternotomy using size (29) Medtronic® HANCOCK II™ MV bioprothesis in seven pigs (n=7). After 4 weeks, MVIV was performed via transatrial approach using the Edward® SAPIEN XT™ valve through left mini-thoracotomy under fluoroscopy guidance, valvular competency assured by echocardiography and ventriculography for both valve types on different time intervals (first day after conventional MVR, 4 weeks later pre-MVIV, and 3 weeks after MVIV). Peri-operative Cardiac CT was employed to assess adjacent structures integrity.Results: Standard bioprosthetic MVR was successfully performed, without complication in all animals. Transvalvular pressure gradients (Pmax 3.77 ± 0.8 mmHg; Pmean 2.1 ± 0.6 mmHg) and transvalvular flow velocities (Vmax 0.97 ± 0.1 m/s; Vmean 0.68 ± 0.2 m/s) were low. All MVIVs were successfully implanted within the bioprosthetic valve in acceptable position without distal or proximal dislocation. Echocardiography revealed intact aortic valve after MVIV deployment. Left ventriculogram demonstrated no severe trans- or paravalvular leaks. Pressure gradients across the MVIV (Pmax 16.7 ± 1.8 mmHg; Pmean 6.2 ± 1.2 mmHg) and flow velocities (Vmax 2.16 ± 0.3 m/s; Vmean 1.1 ± 0.2 m/s) were within tolerable ranges. MVIV procedure time from puncture of the left atrium, valve deployment, to sheath removal was 15.6 ± 1.4 min.Conclusion: We successfully performed trans-atrial MVIV within MV bioprosthesis via left mini-thoracotomy under fluoroscopic guidance in substantially short time. this technique would offer an alternative and safe option for high-risk MVR patients. 
LEGEND: (A, B) Echocardiography post-MVIV; (C, D) 3D-cardiac CT; (E) Ventriculogram
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