Standardized, Angiographically-Guided<br />
“Over-Dilatation” of Stents Using High-Pressure Technique Optimizes Results Without Incre

The introduction of stents in clinical practice resulted in a reduction of the restenosis rate from 30–40% to 16–27% and a target lesion revascularization (TLR) rate of 6–15% after 6 months, although angio-guided stent implantation often resulted in suboptimal stent expansion and significant residual in-stent stenosis.1–6 Intravascular ultrasound (IVUS) has shown that an intrastent minimal lumen area (MLA) of >= 90% of the reference segments, together with complete apposition and symmetric expansion of the stent, or a minimal in-stent area >= 9 mm2 (Table 1) are associated with a low restenosis rate (= 9 mm2 despite optimal angiographic result (= 50% in a native coronary artery. There were no limitations on lesion type, length or site except for bifurcation or thrombotic lesions. Angioplasty and IVUS procedure. The femoral approach was used for stent implantation. The target lesion was predilated using under-sized, conventional angioplasty balloons before stenting. NIR, AVE GFX, ACS GFX, Bard and Jomed stents were used. Stent size was selected to achieve a final stent to artery ratio of 1:1 using semi-compliant balloons with “high pressure”. Optimal stent implantation was defined as = 14 atm. IVUS imaging was then performed following administration of 0.1–0.2 mg of intracoronary nitroglycerin. We used an IVUS system (Cardiovascular Imaging System, Inc., Boston Scientific/Scimed, Inc.) with a 30 MHz transducer mounted on the end of a flexible shaft that rotated at 1,800 rpm (2.9 Fr or 3.2 Fr imaging sheath). Imaging was performed using a motorized transducer pullback device (0.5 mm/s). The IVUS catheter was advanced > 10 mm distal to the lesion and the imaging was performed uninterrupted to the aorto-ostial junction. During the procedure, the patients received bolus doses of heparin to maintain the activated clotting time > 300 seconds. In the control group, IVUS was performed after optimal results were achieved according to angiography (= 9.0 mm2. All stents had good apposition and fulfilled symmetric stent expansion according to MUSIC criteria (symmetry index >= 0.7 in MLA). A minimal in-stent stenosis according to the AVID criteria (MLA >= 90% of the distal reference segment) and MUSIC criteria (MLA >= 100% or >= 90% of the smallest/average of the reference segments) was found in 67% and 57%, respectively (Table 4). In addition, IVUS demonstrated a considerable degree of residual stenosis, in particular at the mid-section of the stent (Table 5). Serious complications unrelated to post-dilatation occurred in 6 patients. Four of these were dissections that were covered by another stent. One patient had a transient “no flow” phenomenon successfully treated with intracoronary nitroglycerin, and a balloon rupture occurred in another patient, causing a small myocardial infarction. There were no deaths. During 1-year clinical follow-up, five patients (17%) had clinically significant re-angina demanding angiography, but only 1 patient (3.3%) had significant in-stent stenosis. The remaining 4 angina patients had neither significant in-stent stenosis nor new significant stenoses in non-stented coronary artery segments. Comparison with non-randomized controls in patients with single-vessel disease (Table 6) revealed no significant difference in baseline characteristics, location of the target lesion or stent type. Pre-intervention MLA as well as stenosis length and complexity were approximately the same in the 2 groups. Post-intervention, the group subjected to over-dilatation demonstrated significantly less angiographic residual stenosis, larger IVUS-derived MLD, more patients achieving MLA >= 90% of the distal reference segment and more patients reaching MLA >= 9.0 mm2. In addition, there were non-significant trends toward a smaller proportion of patients who developed re-angina and need for TVR in the over-dilatation group. DISCUSSION The present study suggests that moderate stent over-dilatation results in improved stent expansion and favorable clinical course without adding complications to routine stent deployment, and can be performed without IVUS guidance. The studies to obtain optimal stent expansion have mainly focussed on high-pressure deployment of the stent and there is still controversy as to whether high pressure or over-dilatation is the best strategy.9,10 A number of studies have shown that long-term outcome, as assessed by control coronary angiography or the need for TVR, is improved by stenting and by the achieved luminal area in the stent. Stent deployment has been shown to be very effective for acute occlusions19,20 and suboptimal PTCA results,21,22 and to reduce restenosis rates.2,5 The initial high incidence of acute/subacute stent thrombosis2,5,23 decreased to 1–2% using balloons equal in size to the target vessel and high pressure in combination with acetylsalicylic acid and/or ticlopidine. In most of the studies, the results were achieved using IVUS-guided stent deployment,13 but a small number of studies suggested that the same results could be achieved without IVUS.24,25 With this approach, the in-stent restenosis rate fell to 16–27% and TLR rate fell to 6–15%.1–6 The efforts to optimize stent deployment with IVUS have focused on different criteria for stent expansion in relation to the reference segments. In the MUSIC study,8 the restenosis rate at 6 months was 9.7% and TLR rate was 4.5% if certain “MUSIC criteria” were filled. The now completed randomized OPTICUS study will reveal whether these criteria are superior to angiographically-guided stent deployment. Preliminary results from another ongoing randomized study entitled AVID (which has different IVUS criteria) indicate that the target endpoint of MLA >= 90% of the distal reference segment was achieved in = 9 mm2 is associated with an in-stent restenosis rate of 3–8%, compared to 30–46% if MLA was = 9 mm2 and only 43% of the stents had a significant residual in-stent stenosis according to strict MUSIC criteria. The AVID criteria for optimal IVUS-guided stent implantation were fulfilled in 67% of the stent deployments, which is an improvement compared to preliminary data from the AVID study. Comparisons with control patients from a study at our hospital in a similar PTCA population who had not undergone post-dilatation demonstrated that in spite of a tendency to tighter stenoses and more occlusions in the present group, over-dilatation seemed to produce better stent expansion. Six patients (20%) developed complications, mainly dissections, which were easily managed with stents. All complications occurred during routine deployment of a stent and the over-dilatation did not add further complications to the procedure. The incidence of complications is not surprisingly high. The incidence of dissections among more than 30,000 patients in the Swedish PTCA register was more than 30%, and 20% had to be stented.17 Interestingly, in the present study, the balloon used for post-dilatation was shorter than the stent, leading to a better and more symmetric stent expansion, although additional damage in the stent margins and the reference segments was minimized. None of the complications, mainly dissections, occurred during the post-dilatation, so it seems feasible to use a balloon size 0.25 mm bigger than the reference diameter obtained by angiogram as long as further dilatations are performed within the stent edges. Study limitations. Most IVUS studies use detailed patient selection criteria, which tends to restrict extrapolation of the results to clinical practice. In the present study and in the control cases, there was a wide spectrum of lesion type and stent type that was representative of most Swedish PTCA centers.17 We did not use strictly defined selection criteria; nevertheless, 40% of the patients were unstable, 44% of the lesions were complex type and 29% of the patients had an occluded artery. It would, however, have been advantageous if strict consecutive inclusions had been applied. The stop-criterion for the angiography-guided PTCA in the present study, i.e.,

1. Moussa I, Di Mario C, Moses J, et al. Comparison of angiographic and clinical outcomes of coronary stenting of chronic total occlusions versus subtotal occlusions. J Am Coll Cardiol 1998;81:1–6. 2. Serruys PW, de Jaegere P, Kiemeneij F, et al. A comparison of balloon-expandable stent implantation with balloon angioplasty in patients with coronary artery disease. N Engl J Med 1994;331:489–495. 3. Morice MC, Aubry P, Benveniste E, et al. The MUST Trial: Acute results and six-month clinical follow-up. J Invas Cardiol 1998;10:457–463. 4. Akiyama T, Moussa I, Reimers B, et al. Angiographic and clinical outcome following coronary stenting of small vessels. A comparison with coronary stenting of large vessels. J Am Coll Cardiol 1998;32:1610–1618. 5. Fischman DL, Leon MB, Baim DS, et al. A randomized comparison of coronary stent placement and balloon angioplasty in the treatment of coronary artery disease. Stent Restenosis Study Investigators. N Engl J Med 1994;331:496–501. 6. Serruys PW, van Hout B, Bonnier H, et al. Randomized comparison of implantation of heparin-coated stents with balloon angioplasty in selected patients with coronary artery disease (BENESTENT II). Lancet 1998;352:673–681. 7. Moussa I, Di Mario C, Moses J, et al. Does the specific intravascular ultrasound criterion used to optimize stent expansion have an impact on the probability of stent restenosis? J Am Coll Cardiol 1999;83:1012–1017. 8. de Jaegere P, Mudra H, Figulla H, et al. Intravascular ultrasound-guided optimized stent deployment: Immediate and 6 month clinical and angiographic results from the Multicenter Ultrasound Stenting in Coronaries (MUSIC) Study. Eur Heart J 1998;1214–1223. 9. Johansson B, Olsson H, Wennerblom B. Angiography-guided routine coronary stent implantations results in suboptimal dilatation according to strict criteria (MUSIC) as assessed by ultrasound. Angiology 2002;53:69–75. 10. Werner G, Diedrich J, Ferrari M, et al. Can additional intravascular ultrasound improve the luminal area gain after high pressure stent deployment? J Am Coll Cardiol 1996;27:225A. 11. Albiero R, Rau T, Schulter M, et al. Comparison of immediate and intermediate-term results of intravascular ultrasound versus angiography-guided Palmaz-Schatz stent implantation in matched lesions. Circulation 1997;96:2997–3005. 12. de Feyter PJ, Kay P, Disco C, et al. Reference chart derived from post-stent implantation intravascular ultrasound predictors of 6-month expected restenosis on quantitative coronary angiography. Circulation 1999;100:1777–1783. 13. Colombo A, Hall P, Nakamura S, et al. Intracoronary stenting without anticoagulation accomplished with intravascular ultrasound guidance (see comments). Circulation 1995;91:1676–1688. 14. Hoffman R, Mintz GS, Mehran R, et al. Intravascular ultrasound predictors of angiographic restenosis in lesions treated with Palmaz-Schatz stents. J Am Coll Cardiol 1998;1:43–49. 15. Russo RJ, Nicosia A, Teirstein PS, et al., for the AVID Investigators. Angiography versus intravascular ultrasound-directed stent placement (Abstr). J Am Coll Cardiol 1997;29:369A. 16. Fitzgerald PJ, Oshima A, Hayase M, et al. Final results of the Can Routine Influence Stent Expansion (CRUISE) Study. Circulation 2000;102:523–530. 17. SCAP (Swedish Coronary Angioplasty Register): 1998. 18. Russo RJ. Ultrasound-guided stent placement. Cardiol Clin 1997;15:49–61. 19. Georg BS, Voorhees WD III, Roubin GS, et al. Multicenter investigation of coronary stenting to treat acute or threatened closure after percutaneous transluminal coronary angioplasty: Clinical and angiographic outcomes. J Am Coll Cardiol 1993;22:135–143. 20. Roubin GS, Cannon AD, Agrawal SK, et al. Intracoronary stenting for acute and threatened closure complicating percutaneous transluminal coronary angioplasty. Circulation 1992;85:916–927. 21. Fischman DL, Savage MP, Leon MB, et al. Effect of intracoronary stenting on intimal dissection after balloon angioplasty: Results of quantitative and qualitative coronary analysis. J Am Coll Cardiol 1991;18:1445–1451. 22. Herrmann HC, Buchbinder M, Clemen MW, et al. Emergent use of balloon-expandable coronary artery stenting for failed percutaneous transluminal coronary angioplasty. Circulation 1992;86:812–819. 23. Nath PC, Muller DWM, Ellis SG, et al. Thrombosis of a flexible coil coronary stent: Frequency, predictors and clinical outcome. J Am Coll Cardiol 1993;21:622–627. 24. Karrillon GJ, Morice MC, Benvenesti E, et al. Intracoronary stent implantation without ultrasound guidance and with replacement of conventional anticoagulation by antiplatelet therapy. 30-day clinical outcome of the French Multicenter Registry. Circulation 1996;94:1519–1527. 25. Goods CM, Al-Shaibi KF, Yadav SS, et al. Utilization of the coronary balloon-expandable coil stent without anticoagulation or intravascular ultrasound. Circulation 1996;93:1803–1808.