Intracoronary ultrasound observations during stent implantation.

Intracoronary Ultrasound Observations During Stent Implantation Shigeru Nakamura, MD; Antonio Colombo, MD; Antonio Gaglione, MD; Yaron Almagor, MD; Steven L. Goldberg, MD; Luigi Maiello, MD; Leo Finci, MD; Jonathan M. Tobis, MD T he Palmaz-Schatz stent has been used success- fully to improve primary angioplasty results, to treat large coronary dissections, or to prevent impending closure of the lumen. -1-5 The determination of successful stent implantation is based on the angio- graphic appearance. However, angiographic projection imaging may not reveal the three-dimensional geometry that is necessary to appreciate full expansion of a cylindrical meshwork device such as the intracoronary stent. Intravascular ultrasound (IVUS) imaging has the advantage of providing detailed cross-sectional images from within the vessel lumen, allowing better evaluation of stent expansion.16-21 Based on angiographic assess- ment, it has been recommended to overdilate the ste- nosis about 10% greater than the reference vessel diameter.1 There is no quantitative guideline for IVUS assessment of successful stent implantation. The pur- pose of this study was to compare the observations of IVUS with standard angiography after stent implanta- tion and to develop recommendations for guiding stent implantation by IVUS. Methods Population and Stent Type The study population consisted of 63 consecutive patients who underwent Palmaz-Schatz stent insertion for native cor- onary arteries and received IVUS imaging at two institutions from January 1, 1993, to April 16, 1993. There were 55 men and 8 women. The mean patient age was 58.6±9.6 years. All patients had coronary artery stenosis with objective evidence of ischemia. Of the 65 lesions treated, the indications for stent insertion were elective implantation in 60 (92%) and emer- gency implantation in 5 (8%). Emergency stent deployment was defined as the presence of a large dissection with threat- ened closure after coronary angioplasty, as evidenced by chest pain and ischemic ECG changes. The target lesion was in the left anterior descending coronary artery (LAD) in 40 lesions, the left circumflex artery (LCx) in 10 lesions, the right coronary artery (RCA) in 14 lesions, and the left main artery in 1 lesion. A standard-length (15 mm) Palmaz-Schatz stent (Johnson and Johnson Interventional Systems) was used in 12 lesions (18%). A short version (7 mm) of the Palmaz-Schatz stent was made by cutting the articulation site22 and was used in 48 lesions (74%). A 10-mm-long biliary Palmaz stent was Received October 8, 1993; revision accepted November 16, From Centro Cuore Columbus (A.C., Y.A., L.M., L.F.), Milan, Italy; Villa Bianca and University of Bari (A.G.), School of Medicine, Bari, Italy; and the Division of Cardiology (S.N., S.L.G., J.M.T.), University of California Irvine. Correspondence to Antonio Colombo, MD, Centro Cuore Co- lumbus, Via Buonarotti 48, 20145 Milan, Italy. inserted in 10 lesions (15%). One stenosis was treated with a 10-mm renal Palmaz stent. The biliary and renal stents were used in heavily calcified lesions because of the additional strength of these larger devices. A single stent was implanted in 18 lesions (28%), and multiple stents were used in 47 lesions (72%). Anticoagulation All patients received aspirin 325 mg and a calcium channel antagonist before stent implantation. Heparin (10 000 U) was administrated intra-arterially at the beginning of the proce- dure and was followed by intravenous infusion to maintain the activated clotting time . 300 seconds. Low-molecular-weight dextran 40 (10%) was administrated (100 mLIhr for 2 hours) and continued at 50 mIlhr for a total dose of 1 L. The sheaths were pulled 1 day after the procedure. Patients were main- tained on a heparin infusion for 4 to 5 days until a therapeutic warfarin dose was achieved with a prothrombin time between 16 and 18 seconds. Patients stayed in the hospital for 7 days after the procedure. Dipyridamole and sodium warfarin were continued for 2 months. Insertion Procedure When the lesion was severe, predilatation was performed with a 2.0-mm balloon using standard percutaneous coronary angioplasty techniques. All stents were manually mounted on a balloon that matched the angiographic reference lumen diameter. The stent was then overdilated with a balloon approximately 0.5 mm larger than the reference lumen diam- eter. To avoid balloon inflation outside of the stented segment of the vessel, a 9-mm-long balloon (Short Speedy, Schneider Europe) was used for final dilatation. The final dilatation was performed at higher pressures, if necessary. The procedure end point was achieved when the operator determined that maximal stent expansion had occurred based on the angiographic evidence of a step up into the stented area and a step down into the distal unstented segment. Ordinarily, the procedure would be terminated at this point, but for the purpose of this study, IVUS imaging was then performed using a 3.9-F monorail system with a 25-MHz ultrasound transducer (Interpret Catheter, InterTherapy/CVIS). The imaging cathe- ter was positioned under fluoroscopic guidance distal to the stent, and images were recorded continuously as the catheter was withdrawn manually through the stented segment. After the stented area was interrogated with a single pullback, the catheter was repositioned to identify the tightest segments within the stented portion. If the operator and ultrasound reviewer believed that there was a possibility to improve stent expansion, further balloon dilatations were performed using a larger balloon or higher pressure. The initial concept was to obtain a lumen cross-sectional area (CSA) approximately 70% of the expected CSA of the chosen balloon. IVUS imaging and balloon dilatation were repeated until a satisfactory lumen area and uniform expansion were achieved or no further improvement could be obtained. Downloaded from http://circ.ahajournals. org/ at CONS CALIFORNIA DIG LIB on October 10, 2015