***TASK***
the task is to simplify the input abstract of a biomedical literature

***INPUT***
the input is the abstract of a biomedical literature

***OUTPUT***
the output is the simplified abstract for the input abstract of a biomedical literature

***DOCUMENTATION***

***EXAMPLES***

Input: A total of 14 trials were included in this review; 4970 patient results were analysed. Four trials evaluating vitamin K antagonists (VKA) versus no VKA suggested that oral anticoagulation may favour autologous venous, but not artificial, graft patency as well as limb salvage and survival. Two other studies comparing VKA with aspirin (ASA) or aspirin and dipyridamole provided evidence to support a positive effect of VKA on the patency of venous but not artificial grafts. Three trials comparing low molecular weight heparin (LMWH) to unfractionated heparin (UFH) failed to demonstrate a significant difference on patency. One trial comparing LMWH with placebo found no significant improvement in graft patency over the first postoperative year in a population receiving aspirin. One trial showed an advantage for LMWH versus aspirin and dipyridamol at one year for patients undergoing limb salvage procedures. Perioperative administration of ancrod showed no greater benefit when compared to unfractionated heparin. Dextran 70 showed similar graft patency rates to LMWH but a significantly higher proportion of patients developed heart failure with dextran. Patients undergoing infrainguinal venous graft are more likely to benefit from treatment with VKA than platelet inhibitors. Patients receiving an artificial graft benefit from platelet inhibitors (aspirin). However, the evidence is not conclusive. Randomised controlled trials with larger patient numbers are needed in the future to compare antithrombotic therapies with either placebo or antiplatelet therapies.
Output:

Surgery to bypass the blockage uses either a piece of vein from another part of the person’s body or a synthetic graft. The bypass may help improve blood supply to the leg but the graft can also become blocked, even in the first year. To help prevent this, people are given aspirin (an antiplatelet drug) or a vitamin K antagonist (anti-blood clotting or antithrombotic drug), or both, to try to stop loss of blood flow through the graft (patency). The review of trials found that patients undergoing venous grafts were more likely to benefit from treatment with vitamin K antagonists than platelet inhibitors. Patients receiving an artificial graft may benefit from platelet inhibitors (aspirin). However, the evidence is not conclusive. Although a total of 14 randomised, controlled trials involving 4970 patients were included in the review, trials with larger patient numbers are needed. This is because there was considerable variation between the included trials in whether patients received both types of drugs, anticoagulation levels and how they were measured, and the indications for surgery, intermittent claudication or critical limb ischaemia.