OBJECTIVETo assess the efficacy and safety of intravascular ultrasound (IVUS)-guided interventional therapy for borderline lesions in patients with acute coronary syndrome (ASC).

METHODSThirty-one ASC patients with borderline lesions (coronary artery stenosis between 40%-70% confirmed by coronary arteriography [CAG]) and a minimal lumen area (MLA) of the infarction related artery(IRA) < or =4.0 mm(2) shown by IVUS underwent percutaneous coronary intervention (PCI). Another 31 PCI cases without IVUS were also enrolled as the control group. The minimal luminal diameter, cross section luminal area, total cross section, plaque area and area stenosis rate were measured before and after stent deployment at a conventional or higher pressure in the IVUS group. All the patients were followed up for 10-12 months and clinically evaluated 1, 3, 6 month and 12 months after the procedure to collect the data of angina recurrence, myocardial infarction and revascularization.

RESULTSAll the 31 cases were successfully stented with satisfied CAG results (with residual stenosis <0, TIMI flow grade III) and without dissection or any related complications. Among the 32 stents, 28 showed insufficient adherence or underexpansion (stent malapposition) to require 18-20 atm dilation or another high pressure balloon to attain the adequate IVUS results. CAG and IVUS were repeated in 22 patients (70.97%) of the IVUS group during the 10 to 12 months of follow up. No stent restenosis occurred with the in-stent diameter late loss >50%, nor was in-stent thrombus found by IVUS. Endomembrane proliferation was found but without any significant difference. Minimal stent lumen area were not significantly different from the immediate results after PCI (10.12-/+1.15 mm(2) vs 8.98-/+2.12 mm(2), P>0.05). The 31 patients in the control group were successfully stented with satisactory CAG results, but 3 suffered angina at 3-6 months who showed stent restenosis and insufficient stent adherence.

CONCLUSIONIVUS can more effectively guide the interventional therapy for ACS borderline lesions and assess the immediate efficacy of therapy than CAG. Post-dilation with higher pressure (16-20 atm) guided by IVUS can further improve the procedural results. IVUS-guided PCI for ACS borderline lesions ensures high immediate and long-term success rate.