Monday, 19 September 2011

THE PROSTHETIC VALVE PENDULUM THAT IGNORES THE EVIDENCE

There are 2 types of prostheses that are used to replace diseased heart valves - mechanical and biological. Randomised studies have shown 2 differences between the 2 - biological prostheses are more likely to degenerate over time, especially if the age of the patient at implantation is under 65-70,   & patients receiving mechanical valves and who are therefore anticoagulated, are more likely to suffer an anticoagulant related haemorrhage. That's it.

And yet the age cutoff point used by surgeons to implant biological prostheses has moved up and down like a yoyo (or swung like a pendulum). It's not evidence that has driven these changes - it's disaster stories (mechanical valves falling to pieces!) and that unethical beast  - marketing.
I blogged recently about the Aristotle study showing the superiority of yet another new anticoagulant over warfarin as regards both the ying of thromboembolism and the yang of bleeding in patients with atrial fibrillation. Apart from having superior outcomes over warfarin, these new drugs have a fixed dose and do not require frequent measurement of the INR. (blood test - International Normalised Ratio). These new drugs will, I predict,  cause the pendulum to swing back towards mechanical prostheses (which are now super sturdy!) - if it suits the valve big boys and their investors, that is!! TAVI (transcutaneous aortic valve implantation) devices (biological and very profitable) may prove me wrong, even if it is the wrong choice for many patients.