BACKGROUND: PTCA is often unsuccessful in a patient with chronic total occlusion of coronary arteries with success rates varying from 60 to 70%. Success rates are related to the duration of total occlusion, longer occlusions being associated with lower success rates. Chronic total occlusion may be associated with thrombi superimposed on the stenotic lesion. We used an intra-coronary bolus of urokinase followed by a prolonged urokinase infusion in an attempt to lyse the lesion and allow for passage of the PTCA wire during subsequent angioplasty. The purpose of prolonged durokinase infusion was to reduce the clot sufficiently to recanalize the coronary artery and make it more amenable to PTCA. METHODS: Study patients: We were included six patients who developed total occlusion for more than 3 weeks and good collateral channels of Grade 2 or more and previous attempts at angioplaty had failed. Procedures: All patients underwent dual catheter system and incremental dose protocol of intracoronary urokinase infusion. RESULTS: The mean duration of occlusion was calculated to be 65.3+/-2.7 weeks and urokinase dose ranged from 130,000 to 200,000U/hr and treatment lasted 21.7+/-1.4 hours in our study. The prolonged urokinase infusion resulted in reperfusion of the occluded dvessel in 5 of the 6 patients(83%), with or without the complementary balloon inflation. One patient failed to recanalize the occluded vessel because cardiac tamponade was developed during the prolonged urokinase infusion. CONCLUSION: We concluded that the prolonged urokinase infusion in occluded coronary artery appeared to increase the likelihood of successful PTCA in patients with chronic total occlusion of coronary arteries.Also, in carefully selected patients, prolonged urokinase infusion in occluded coronary artery was relatively safe and well tolerated.