MECHANICAL VALVES Vs BIOPROSTHETIC VALVES IN THE AORTIC POSITION. LATEST DATA

I have seldom written about valve surgery as I did not consider it in the realm of interventional cardiology, until the recent trends at live demo meetings to showcase " Transcatheter Aortic Valve Implantation " or TAVI. It looks like coronary interventional cardiology has reached a plateau and interventional cardiologist ( those jack of all trades ) have gone onto start a new frontier, as it were. So I began to keep an eye on what is happening there. Over this week, the Society of Thoracic Surgeons are holding their 2011 annual scientific meeting at San Diego. One of the papers presented was a piece of work by the cardio-thoracic team at University of Berne, led by Dr Alberto Weber. They studied the 10 year outcome of bioprosthetic aortic valve replacement ( in this case the Carpentier Edwards valve ) against the mechanical aortic valve ( the St Judes valve ) in a relatively young population ( less than 60years ). They found in their series, that both the valves performed equally well in terms of MACE, but the patients who had the bioprosthetic valves had significantly less 10years survival. This reduce 10 years survival was not due to re-do operations. In a way, this was surprising. We are puzzled.
Sometimes, young people, still full of athleticism, will op for a bioprosthetic valve to avoid the long term use of anticoagulations like warfarin. Now they can even reason that should I need a re-do, I can op for a TAVI ( at the moment, no such indication). We were always taught that a mechanicxal valve last much longer, and the St Judes, bi-leaflet, mechanical valve is durable and performs well mechanically. When the Swiss team measure the indices of function between the two groups, they found no significant difference between the two groups. Why then did the bioprosthetic group lived shorter? I suppose it may be because, the cardiac surgeons may have selected the younger patients with more co-morbidities to implant the bioprosthetic valves, knowing that the other co-morbidities will limit their lifespan. Afterall, this is not a prospective randomised trial but a propensity score, comparison trial.
I think it is also fair to say that the Carpentier Edwards valve by Edward Lifesciences, is not the lastest in bioprosthetic valve technology. I understand that there is a second generation Hancock's by Medtronic, that is theorectically superior, in terms of hemodynamics.
It is therefore understandable that Edward Lifesciences and Medtronic International is also heading the march to produce valves for TAVI.
Fiinally, a word about anti-coagulation. It used to be that warfarin was standard anti-coagulation for all mechanical valve replacements. Then we learned that in the aortic position, the warfarin need not be lifelong. Being in a high flow situation, even for mechanical valves, warfarin for 1-2 years may suffice and in many of my patients, I have successfully switched them to aspirin and they are still doing well. Nowadays, we have dabigatran ( a factor 10 inhibitor ) as a safer ( but much costlier ) anti-coagulant.
There have been some advances in cardiac valve surgery, but obviously not as much as was in interventional cardiology, over the last 20 years.
But know that I am of course bias, since I am an interventionist.