RCB said:
"mechanical valves suffered from this sort of damage resulting in either failure"
Could you point out to me the report of a valve that failed due to cavatation?
The problem is damage causes wear- NOT waring out! The point of these studies is to understand the wear process and to improve mech. valves. Nothing in these studies said that mech. valves weren't durable. It kind of like stating that you when you replace the tires on your car, heat and friction
will cause damage to the tire- while that is true, it is normal. Lets face it- life wear us out, ending badly for us all.
here is something on the fda web-site -- a bit dated ... 1995, newer mechanical valves are better
http://www.fda.gov/cdrh/ost/reports/fy95/fluid.html#anchor1668654
and an article whose full text I couldnt find:
http://www.ncbi.nlm.nih.gov/entrez/...d&dopt=Abstract&list_uids=10503622&query_hl=7
Without being an expert in any sense on mechanical valves, here is what I picked up during my decision phase:
Mechanical valves obviously work very well for many poeple ... there are many healthy, active people on this site with them. They rarely fail and are your best bet if you want to avoid another valve surgery.
The catch is something about their dynamics/interaction causes changes in blood chemistry and deterioration in the smooth surface of the valve, many researchers think it is the rate of pressure and temperature changes around edges as they accelerate and decelerate while opening and closing. This leads to a statistically greater chance of clot formation as the valve ages, from what I have read this does not happen with tissue valves.
Early valves were explanted with cavitation induced failure; new smooth, hard surfaces ( pyrolytic carbon ) are better at resisting damage due to cavitation but the mechanism which induces cavitation still exists -- creation of regions of low pressure around sharp, hard edges.
This is the main argument for tissue valves and why many clinics implant them even when they eventually cause re-stenosis and need replacement.
I think everyone who studies their options while facing VR knows much of this in one guise or another -- meaning I have just been stating the "first principles" of VR:
-- mechanicals last longer but require anti-coagulation to resist side-effects due to blood damage.
-- tissue valves deteriorate faster than native valves and mechanical valves and many people will need to almost certainly face multiple surgeries.
and according to some papers, which make sense to me:
-- Mechanical valves have a mechanism by which their surface erodes ( due to friction from imperfect materials and design )
My hope for myself is -- by the time I need repeat VR there is a new valve on the market which has a good enough hemodynamic profile to not cause progressive damage to blood chemistry, and is biocompatible and durable enough to last me the rest of my life. BONUS: it can be implanted via catheter.
( promised myself I wouldnt get long winded on this subject -- but there's a song in my native tongue which says: No worthy promise is easy to keep ... or something like that
Best of luck to all who need to make this decision -- its not an easy one and it helps to talk about it to a large extent, but a vast majority of people end up ok either way.
