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Posts Tagged ‘tavr tavi’

TAVR is the new state of the art Aortic valve replacement procedure done by cardiologists .Nearly 200 thousand implants have been done , and it is
backed up by major trials TAVI TAVR valve dislodgement embolism partent a b What keeps the Aortic prosthesis in situ in the aortic root/Annulus  ?

The valve is not actively fixed but passively positioned in aortic root by either self expanding or balloon expanded valve  system .It retains the position by two different forces acting on the valve in two difffernt directions , but work coherently to keep the valve static .The radial force of the hardware is centrifugal and the elastic force exerted by annulus is centripetal .It may appear mysterious how these oppose each other in a balanced way and arrest the valve in the desired site. Fortunately, there is little  supero- inferior force operating and hence the chances of dislodgement is low .It should also be mentioned we are not yet clear about the best site for TAVR. Annular , supra annular ,or is it at lower virtual annulus , all has some advantages and disadvantages.

Is progressive aortic annular dilatation possible in these degenerative aortic valve ?
Aortic stenosis is chronic degenerative disease. Generally we expect the annulus is narrow and fixed. However for some reason if the aortic annulus loses it constricting force or the root dilates or fresh calcium deposits, there is definite risk  (Not theoretical :See Reference ) of valve destabilisation  , dislodgement and embolisation . *It is vital to understand the para-valvular leak could be a  remote precursor of such potential dislodgement as it represents  micro gaps  in the prosthetic / tissue interface.

How many such  embolisation of valves  are reported following TAVR ?

While the incidence of para valvular leak is common ,(up to 20%) fortunately valve embolisation is reported between .3 to 7.5% (Ref 2). Stastically , subclinical   destabilisation, malpostion  and dislodgement should be more common. The timing of displacement is not clearly reported in literature .It can occur  at any time between few hours after implantation to a much delayed (months after ) complication .

Final message

TAVR is a major break through in Interventional cardiology .It gives us hope for possible TAMR (mitral) and other valve repair modalities .Though dislodgement of prosthesis appear a rare event it is tempting  to ask ,  whether we should work towards a actively fixing valve in aortic root ? That remains a open question !

Reference

1. A survivor of late prosthesis migration and rotation following percutaneous transcatheter aortic valve implantation. Pang PY, Chiam PT, Chua YL, et alEur J Cardiothorac Surg 2012;41:1195-6.

2.Thirty-day results of the SAPIEN aortic Bioprosthesis European Outcome (SOURCE) Registry: A European registry of transcatheter aortic valve implantation using the Edwards SAPIEN valve.Thomas M, Schymik G, Walther T, et al. Circulation 2010;122:62-9.

3.Migration of the transcatheter valve into the left ventricle Christopher Cao , Su C. Ang , Michael P. Vallely Mart Annals of Cardiothoracic Surgery Vol 1, No 2 (July 2012 4.Delayed Transcatheter Heart Valve Migration and Failure Vuyisile T. Nkomo, Rakesh M. Suri, ,J Am Coll Cardiol Img. 2014;7(9):960-962.

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Welcome to the  future of  valvular heart disease . This is just the beginning.Expect more dramatic break through  . (Already mitral valve prototype is in advanced stages of development .)

Currently we have two approved percutaneous aortic valves for use in isolated Aortic stenosis. The Edwards valve is popular in  USA  ( 2011 ) and Medtronic  is used extensively in  Europe (From 2007)

Though both valves appear suitable .There are major differences in the concept , design , and technique of implantation .

tavi edward sapiens vs medtronic core valve

Reference

Major  issues to be addressed. Late onset Para valvular leak :
Please remember, these valves are not sutured around the aortic annulus ,  which our surgeons do it meticulously . The force that keep the valve  within the  aortic root is nothing but the disease process itself . The stiffened, elastic aortic root .(Does it appear  foolish to expect the diseased  aorta to hold the valve in situ ? but that is the reality  ! )
If the aortic root  dilates  for  some reason  which is very likely in  atherosclerotic  process    the very foundation of valve is shaken and para valvular leak is certain.

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