Sorry for your news, I hope you are feeling better. It's very important to find out why this happened. Did you have recent leg trauma, immobility, injury?? If a true precipitating event caused this, then maybe the coumadin could be for just 6 months. If this is truly "idiopathic" meaning no explanation can be found, then the data is confusing, and the current consensus is treat indefinitely. At least until more clinical trials prove otherwise. It's also important that you make sure you are up to date on health maintenance issues, eg. colonoscopy, usual screening stuff. I'm sure the docs will check you for genetic clotting disorders as well, most common ones include Factor 5 Leiyden and Prothrombin Gene Mutation. Difficulty with these tests is knowing whether they truly were the reason for your clot.
Greenfield Filters are usually reserved for those with tremendous clot burden, and/or compromized right heart function as a result of the clots where any further clots could be fatal. Filters are also used when anticoagulation cannot be used, eg. if you were to be bleeding or need major surgery. If you don't fit this category, in general we don't put in Greenfield Filters as they can cause problems long term
(filter is simply a device put into your Inferior Vena Cava to theoretically "catch" any blot clot that tries to travel from your legs to you lungs
), and clots can still form on a filter.
Coumadin is a tough drug to be on, but know that in the future there is a new drug that may replace coumadin, and will not need to be monitored with regular blood draws. It's still investigational in the US but appears very promising and the initial data looks good.
Taking coumadin and biking is more of a risk decision you make for yourself. Personally, if I end up on coumadin and am still physically able to cycle safely, I would do it. It's a personal choice for me. Make sure you get a medical warning wrist band or something that allows people to know you are on this medication if you do resume biking.
Again, so sorry this happened to you. Here's to a fast recovery. My best, Jim