[HSF] ATS valve

[Rwmfglycar at aol.com]

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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