Hi Bionic Man,
I?d like to discuss some of the physiology of clotting that your questions bring up. However, I must first dissuade you from thinking that you are ?bionic?. When you have time do a Google search on the terms bionic and Steele. I was fortunate to work in the same USAF laboratory as Major Steele who coined the term bionics. It loosely means applying biological methods to engineering designs. You, my good friend merely have very expensive replacement parts. There is nothing about a heart valve that is bionic. It merely is a mechanical valve that is sewn into the heart.
Steve Austin played by Lee Majors in actuality was a cyborg. A cyborg refers to an organism that is a mixture of organic and mechanical parts. Unfortunately for the definition of bionics, this cyborg character was placed in a popular TV program called the ?Six Million Dollar Man? In the opening credits of the show, Oscar Goldman says, "Gentlemen, we can rebuild him. We have the technology. We have the capability to make the world's first bionic man. Steve Austin will be that man. Better than he was before. Better... stronger... faster." Thus the misconception of bionics took root in the American culture.
In spite of all of this, enjoy the life and function given to you by an expensive technology.
You indicated some questions about the INR test in relation to taking Lovenox and being off of Coumadin. Each of these two drugs affects different aspects of the clotting mechanism. They each need to be evaluated by different tests. The effect of Coumadin is tested by the INR, which measures the amount of prothrombin. Lovenox is tested by measuring the ptp (partial thromboplastin).
The risks of not being anticoagulated are NOT removed by bridging therapy. All it does is reduce the time that you are not anticoagulated. This is a function of the rapidity with which the drug effect dissipates. For a surgical procedure with major risk of blood loss and complications, the risk benefit ratio of bridging makes sense. For procedures with less risk of bleeding then bridging is NOT the method of choice, while being anticoagulated in the 2-3 range is preferable.
Let me finally point out how clots are formed on heart valves. Clots are formed by either an intrinsic or extrinsic mechanism, which meet into a common pathway. Simply, the intrinsic pathway starts when platelets come in contact with the damaged inner lining of blood vessels. This occurs with trauma such as cutting oneself. The extrinsic pathway is in part stimulated by platelets adhering to an unusual surface. A heart valve, even though made of smooth material gets covered with proteins from the blood stream and act as a focus for platelets to adhere. The Coumadin significantly reduces the chances of adhesion and further formation of clots.
