Sunday, 31 July 2011

BIOLOGICAL OR MECHANICAL , WHO KNOWS ?


Aortic Valve Replacement: A Prospective Randomized Evaluation of Mechanical Versus Biological Valves in Patients Ages 55 to 70 Years -- Stassano et al. 54 (20): 1862 -- Journal of the American College of Cardiology
A surgical randomized controlled study is always welcome and worth commenting on - they are difficult to organise and expensive and consequently they are rare.
The age group the triallists chose for this RCT comparing mechanical and biological valves in the aortic position is quite unusual. The current commonest cut off age for deciding which prosthesis to choose is 65 - unless there are contraindications to anticoagulation, patients who are under 65 will get a mechanical prosthesis whilst those above, a biological. This trial does not therefore provide evidence required to move that cut off point up or down.
I have only read the abstract and I have only made the assumption that patients receiving mechanical valves were anticoagulated whereas those receiving biological valves were not - this is standard practice. The regimen chosen in this trial was not mentioned in the abstract. If standard practice was employed, it is surprising that there was no difference between the groups in the incidence of anticoagulant related bleeding episodes. Patients on long term oral anticoagulants are always more likely to suffer bleeding episodes - that's how anticoagulants work. The flip side of anticoagulant related haemorrhage is thromboembolism. It is possible that a lowish maintenamce INR was chosen for the patients in this trial that resulted in equipoise between bleeding and thromboembolism. Maybe all patients in both groups were anticoagulated.
Maybe I should read the paper!!

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