Unfortunately, there is no good data for any of this. One option, however, is to be bridged with heparin until the day of the surgery (heparin has a very short half life and can be discontinued few hours prior to the operation) and then restarted a day after his operation assuming that there are no complications. Some also advocate doing a TEE to see if there is clot in the left atrium and if so postpone the operation until it resolves. This is something one might recommend in someone with high risk for clot such as heart failure, DM, previous embolic stroke, etc. It is generally quite safe to come off coumadin prior to these types of surgeries and this is typically what is done here at the cleveland clinic. Again, high risk patients could consider bridging with heparin.