Comparison of clinical, angiographic, and intravascular ultrasound parameters after direct stenting versus predilation

Abstract

T use of coronary stents has increased exponentially over the last decade since 2 large randomized trials demonstrated that stents decrease restenosis and increase event-free survival at 6 months.1,2 Currently, a stent placement is recommended for all coronary lesion types in coronary vessels 2.7 mm, bypass lesions, and restenotic lesions, as well as “bail out” situations.3–5 The standard stent implantation technique requires routine predilation with a balloon catheter to allow an easy passage of the stent and to enhance a complete expansion of all stent modules. Improved stent design has enabled placement of stents without predilation.6 In addition to a decrease in procedural time and radiation exposure, direct stenting may cause less trauma of the vessel wall.7–10 However, the magnitude of stent expansion and the incidence of restenosis after direct stenting has not yet been fully assessed.11 Therefore, it was the aim of this report to determine stent expansion patterns following direct stenting versus predilation by intravascular ultrasound (IVUS) and to compare the rates of restenosis and major cardiac events at 6 months of follow-up. • • • Between January 2000 and July 2001, 82 patients with 86 de novo coronary lesions and a clinical indication for stenting of a native coronary artery were prospectively enrolled in the study. Written informed consent was given 12 to 24 hours before intervention. Clinical follow-up was obtained for all patients. Angiographic follow-up after 6 months was achieved in 79 patients (84%). Coronary angioplasty was routinely performed by the femoral approach. Heparin 7,500 U was given as a bolus dose after sheath insertion, and repeated doses of heparin 2,500 U were given during the procedure to maintain an activated clotting time of 250 seconds. Implantation technique, balloon size, and inflation pressure were chosen at the discretion of the physician. In all cases, a Multilink Tristar stent (Guidant, Temecula, California) was used. Angiographic success was defined as a final residual stenosis of 20%. IVUS studies were performed immediately after stent implantation, and intracoronary administration of 200 g of nitroglycerin was implemented by using single-element 30MHz transducers rotating at a frequency of 1,800 rpm; these were withdrawn automatically at a speed of 0.5 mm/s (Cardiovascular Imaging Systems, Inc., Sunnyvale, California). Complete imaging runs were obtained from beyond the stent to the aorto-ostial junction. The imaging protocols were recorded on superVHS tapes. After stent implantation, all patients received aspirin (100 mg/day) and clopidogrel at an initial dosage of 300 mg, and 75 mg/day for the subsequent 4 weeks. Angiograms were obtained in multiple projections in identical views at baseline, immediately after stent placement, and at follow-up after 6 months. Angiograms were analyzed by 2 independent observers. Quantitative coronary angiography was performed by analyzing the digitally stored images before and after stent implantation using the Quantcor-software (Siemens Medical Systems, Munich, Germany). The length of the stenosis was estimated with an electronic caliper and the catheter tips were used for calibration. The diameters of the proximal and distal reference segments were averaged by the system to yield the reference luminal diameter, the minimal luminal diameter, and the percent diameter stenosis. Lesions were classified in accordance with the American Heart Association/American College of Cardiology. Anterograde blood flow was graded using the Thrombolysis In Myocardial Infarction trial classification. In-stent restenosis was defined as a 50% diameter stenosis at the stented lesion site. For the purpose of this study, IVUS was performed after stent implantation to assess the pattern of stent expansion. The border of the media adventitia was manually traced at the external elastic membrane to calculate the vessel area. Similary, the stent was manually traced to calculate the stent lumen. The reference segments of the stented coronary artery were defined in close spatial relation to the stented vessel site. Reference artery measurements were obtained directly at both sides of the stented arterial segment. An optimal cross section of both the proximal and distal reference segments was chosen to trace and calculate the lumen as well as the vessel area. The complete pullback within the stented segment was carefully reviewed by 2 independent observers for identifying and calculating the tightest intrastent lumen. In addition, stent expansion at the tightest in-stent site was assessed by a stent symmetry index (minimum stent diameter/maximum stent diameter). In this model, a stent symmetry index of 1.0 indicates a perfectly expanded circular stent, From the 1. Department of Medicine, University of Mannheim, Faculty of Heidelberg, Mannheim, Germany. Dr. Haase’s address is: 1. Medizinische Klinik, Universitatsklinikum Mannheim, Theodor-KutzerUfer 1-3, 68167 Mannheim, Germany. E-mail: karl.haase@med.ma. uni-heidelberg.de. Manuscript received July 8, 2002; revised manuscript received and accepted September 17, 2002.