This study evaluated the safety of intracoronary stent placement without anticoagulation when adequate stent expansion is achieved, using intravascular ultrasound (IVUS) guidance. From March 1993 to January 1994, 359 patients underwent Palmaz-Schatz stent insertion. After initial angiographic success with <20% stenosis, IVUS was used to guide further balloon dilatation. Patients with adequate stent expansion confirmed by IVUS were treated only with antiplatelet therapy (ticlopidine or aspirin). Clinical success at 2 months was achieved in 94% of patients (338/359). At 2-month follow-up, there were two acute stent thromboses (0.6%) and one subacute thrombosis (0.3%). At 6 months, 5 patients had stent occlusions (1.6%), and 5.7% had myocardial infarction, 6.4% had coronary bypass surgery, and 1.9% died. Emergency intervention for stent thrombosis occurred in 3 patients (0.8%). Intraprocedural complications occurred in 16 patients (4.5%), but decreased to 1% when appropriately sized balloons were used. By 6 months, 47 patients had repeat angioplasty for symptomatic restenosis (13.1%). The study concluded that the Palmaz-Schatz stent can be safely inserted in coronary arteries without subsequent anticoagulation if stent expansion is adequate and there are no other flow-limiting lesions. High-pressure final balloon dilatations and IVUS confirmation of adequate stent expansion ensure that anticoagulation can be safely omitted. This technique reduces hospital time and vascular complications and has a low stent thrombosis rate. The study found that stent thrombosis may be caused in part by incomplete stent dilation rather than the inherent thrombogenicity of the metallic stent. IVUS was crucial in assessing adequate stent expansion, which was frequently underestimated by angiography. The most frequent site of potential flow limitation was within the stented segment. After IVUS-guided repeat dilatations, the intrastent lumen CSA was significantly enlarged, from 6.5 to 8.8 mm². Stent thrombosis was rare despite the absence of anticoagulation. The study compared the results with previous studies and found that the overall clinical success and complication rates were favorable, even in a complex patient cohort. The 6-month event rate was only slightly higher than in multicenter trials on single stent implantation. Procedural complications and inclusion of patients with low ejection fraction contributed to the cumulative high death rate reported at 6 months. The study suggests that IVUS-guided stent implantation without anticoagThis study evaluated the safety of intracoronary stent placement without anticoagulation when adequate stent expansion is achieved, using intravascular ultrasound (IVUS) guidance. From March 1993 to January 1994, 359 patients underwent Palmaz-Schatz stent insertion. After initial angiographic success with <20% stenosis, IVUS was used to guide further balloon dilatation. Patients with adequate stent expansion confirmed by IVUS were treated only with antiplatelet therapy (ticlopidine or aspirin). Clinical success at 2 months was achieved in 94% of patients (338/359). At 2-month follow-up, there were two acute stent thromboses (0.6%) and one subacute thrombosis (0.3%). At 6 months, 5 patients had stent occlusions (1.6%), and 5.7% had myocardial infarction, 6.4% had coronary bypass surgery, and 1.9% died. Emergency intervention for stent thrombosis occurred in 3 patients (0.8%). Intraprocedural complications occurred in 16 patients (4.5%), but decreased to 1% when appropriately sized balloons were used. By 6 months, 47 patients had repeat angioplasty for symptomatic restenosis (13.1%). The study concluded that the Palmaz-Schatz stent can be safely inserted in coronary arteries without subsequent anticoagulation if stent expansion is adequate and there are no other flow-limiting lesions. High-pressure final balloon dilatations and IVUS confirmation of adequate stent expansion ensure that anticoagulation can be safely omitted. This technique reduces hospital time and vascular complications and has a low stent thrombosis rate. The study found that stent thrombosis may be caused in part by incomplete stent dilation rather than the inherent thrombogenicity of the metallic stent. IVUS was crucial in assessing adequate stent expansion, which was frequently underestimated by angiography. The most frequent site of potential flow limitation was within the stented segment. After IVUS-guided repeat dilatations, the intrastent lumen CSA was significantly enlarged, from 6.5 to 8.8 mm². Stent thrombosis was rare despite the absence of anticoagulation. The study compared the results with previous studies and found that the overall clinical success and complication rates were favorable, even in a complex patient cohort. The 6-month event rate was only slightly higher than in multicenter trials on single stent implantation. Procedural complications and inclusion of patients with low ejection fraction contributed to the cumulative high death rate reported at 6 months. The study suggests that IVUS-guided stent implantation without anticoag