ORAL ANTICOAGULATION IN THE PREVENTION OF ONE-YEAR VEIN GRAFT OCCLUSION AFTER AORTOCORONARY BYPASS-SURGERY - OPTIMAL THERAPEUTIC RANGE AND PRACTICAL LIMITATIONS

To assess the optimal level of oral anticoagulation to prevent occlusi on of vein coronary bypass grafts, 318 patients from a graft patency t rial were analysed retrospectively. Oral anticoagulant therapy was sta rted one day before surgery and continued for one year, after which gr aft occlusion was assessed by angiography. The aimed level of anticoag ulation was 2.8-4.8 International Normalized Ratio (INR). Clinical out come was assessed by the incidence of myocardial infarction, thrombosi s and major bleeding. The observed anticoagulation level was 2.8-4.8 I NR for 54%, and 1.8-3.8 INR for 75% of time per patient. Occlusion rat es in patients who spent <35, 35-70, and greater than or equal to 70% of time within INR range 2.8-4.8 were 10.5%, 10.8% and 11.8%, respecti vely (differences not statistically significant). Patients who spent g reater than or equal to 70% Of time within INR range 1.8-3.8 versus 2. 8-4.8 showed comparable occlusion rates. The risk of graft occlusion w as not related to quality of anticoagulation early (0-3 months) or lat e (3-12 months) after surgery. Myocardial infarction, thrombosis and m ajor bleeding occurred in 1.3%, 2.0% and 2.9% of patients. To maintain vein graft patency in the first postoperative year by oral anticoagul ation, a level within INR range 1.8-3.8 for greater than or equal to 7 0% of time seems to be sufficient.