[HSF] ATS valve

[Rwmfglycar at aol.com]

D4ear Prasanna,
As I said Prasanna,
While there is a dramatic difference using a single tilting disc valve with  
the large orifice opening into the greater curve v. the lesser curve, this  
difference is less with the two major orifices of a bileaflet valve  openig into 
the greater curve  v. one opening into the greater curve and  one into the 
lesser curve.
There is literature for the mitral position (starting in a book published  in 
1969) but not much on the aortic position. Here I must make a confession, I  
base my opinion on much observation in vitro of the behaviour of all sorts of  
valve leaflets under pulsatile flow with  a variety of up and downstream  
obstructions. I have also seen impeded movement and even thrombosis when one of  
the orifices of a bileaflet valve was placed over a hypertrophied septum. I  
never got around to writing this up. When you have observed these phenomena  
enough you don't look for p numbers: there is no reason to doubt the  
responsiveness of the leaflets to  fluid dynamic laws. 
Bob
 
In a message dated 6/19/2007 3:51:08 P.M. Eastern Daylight Time,  
prasannasimha at gmail.com writes:

I got  what you meant but this would be about 30 -40 Deg off Joachim 
Laas's  positioning as mentioned by Bojan. The greater curvature 
orientation of  the monoleaflet valves has been well described but there 
seems to be a  paucity of data wrt bileaflet valves and i remember seeing 
a supercomputer  simulation study of these in a model aorta and the 
simulation was spot on  for the monoleaflet valve but no position seemd 
to be better for a  bilaflet valve. That is what started my confusion. Is 
there any literature  to support theseptalbulge to aortic greater 
curvature position  ?
Prasanna
Rwmfglycar at aol.com wrote:
> Dear Prasanna,
> That  is a fair description but since the positions of coronary ostia do  
vary  
> I would prefer for you to look carefully down into the ventricle and  see  
> where the septum is and whether it has a bulge and then  look at the aorta 
and  
> see how the curve lines up; you want the  hinge line to bisect the curve so 
that  
> there is equal access of  each orifice of the bileaflet valve to the space  
> that the  greater curve supplies. For the Medtronic Hall the larger orifice 
must   
> be placed so that the flow through it is  directed to the  greater  curve.
> Placing the latter valve the other way around  actually produces more of a  
> difference in flow patterns than  placing a bileaflet valve with one  
orifice 
> opening to the  lesser curve and one to the greater curve.
> I am reluctant to get into  the current discussion on ATS valves. I have as 
 
> you all know a  consultant job with SJM. The hinge on the ATS looks good 
and  
>  does not have the spaces that recessed hinges of other bileaflet  valves  
have 
> had. The claim however that an open hinge will definitely result  in  a 
lower 
> embolism and thrombosis rate than a recessed hinge  is a marketing claim.  
Some 
> designs with recessed hinges from a  variety of companies have turned out 
to  
> develop thrombi in the  recesses. By good luck more than design the SJM 
hinge  
> over the  last 30 years has performed very well and as advanced methods of  
 
> studying fluid flow at the hinges have come along they have confirmed  good 
flow  
> patterns in the SJM hinge area and revealed  undesirable flow patterns  
that 
> explained hinge thrombosis in  other bileaflet valves.
> There are some studies of ATS that report good  performance but I will have 
 
> to dig through my files to  find  comparative studies with other valves. 
> The hinge of course  is not the only site of thrombus formation in 
bileaflet  
> valves.  There are separate trials underway in which the SJM and  Onyx are 
used  
> with aspirin and plavix. With regard to lower INR's the  current  AHA ACC 
> guidelines advise 2-3 for low risk patients with "newer   generation 
valves", by 
> which the authors mean pyrolytic carbon  bileaflet  valves.
> Bob
>   
>
>
>
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