Organo Ufficiale della Società Italiana di Cardiologia Invasiva

Home - Caratteristiche editoriali - Direttori e segreteria scientifica - Istruzioni per gli autori

Coronary stents are an frequently used for treatment of symptomatic coronary artery disease. Their efficacy was shown in two pivotal trials, the BENESTENT¹ and STRESS study² . In both trials however, the protocol included only vessels of 3 mm or larger diameter by visual estimate. Consequently, stenting was only recommended as a treatment option for larger vessels³ . However, smaller vessels constitute a large group in daily practice of percutaneous coronary interventions. Our own database indicates that 1/3 of patients have lesions located in vessels <2.8 mm by quantitative measure­ments⁴ . Recently, several randomized trials comparing elective stent placement with balloon angioplasty in small vessels have been completed. This review will summarize these findings to address the impact of stent placement on long-term outcome in small coronary vessels.

 Why are small coronary arteries different ?

 Small vessel size has been identified as an independent risk factor for the development of restenosis after balloon angioplasty without stent placement^5,6 . Several retrospective analyses have compared long-term results of stent placement in small versus large vessels, indicating that restenosis rates differ significantly with vessel size. Elezi et al. found that restenosis rate increased from 20.4% in vessels >3.2 mm to 28.4% in vessels 2.8-3.2 mm, and to 38.6% in vessels <2.8 mm (p<.001)⁴ . Similar findings were described by Akiyama et al., with a rate of 19.9% in vessels ³3 mm, and 32.6% in vessels <3 mm (p=.0001)⁷ . Both studies show that this negative effect is the result of simple arithmetics: first, the initial acute lumen gain after stent placement in smaller vessels is significantly lower than in large vessels. Second, both trials have found that late lumen loss after six months is higher in small vessels than in larger vessels. Both effects lead to an even more pronounced decrease in net lumen gain, with a signifi­cantly higher loss index and restenosis rate after six months. In large vessels, signifi­cantly lower restenosis rates have been found after stent placement than after balloon angioplasty in the BENESTENT and STRESS studies^1,2 . In these trials, late lumen loss was also significantly higher after stenting in comparison to balloon angioplasty. However, the final positive net effect of stent placement was due to a significantly higher initial lumen gain with a higher net lumen gain. In view of the above-mentioned findings in small versus large vessels, data from trials in large vessels should not be extrapolated to smaller vessels.

Within the last few years, several dedicated randomized trials on small vessel stenting have been performed. The findings from these studies are summarized in Table 1, and discussed in more detail below.

The first published randomized trial had been conducted in Korea by SW Park et al.⁸ . In this study, 120 patients with de-novo, non-ostial lesions with reference diameter <3 mm by visual estimate were randomly assigned to either balloon angioplasty of placement of 7-cell NIR stents (Boston-Scientific/Scimed). Stent placement was successful in all 60 patients assigned to stent placement; 12 of 60 patients assigned to PTCA were crossed over to stent. Vessel size was similar in both groups (2.48±0.24 mm in PTCA group, 2.55±0.16 mm in the stent group). The final minimal lumen diameter achieved was significantly smaller in the PTCA group (2.14±0.37 mm) than in the stent group (2.42±0.36 mm; p<0.05). However, at follow-up angiography (obtained in 92.5% of eligible patients), this initially observed benefit was reversed, with a minimal lumen diameter of 1.53±0.48 mm in the PTCA group, and 1.33±0.68 mm in the stent group; restenosis rates were 30.9 and 35.7%, respec­tively. Due to the low number of patients randomized, this difference failed to reach statistical significance.

In the ISAR-SMART (Intracoronary Stenting or Angioplasty for Restenosis Reduc­tion in Small Arteries) trial⁹ conducted at three centers in Germany, 404 patients with lesions in native vessels between 2.0 and 2.8 mm by visual estimate were randomly assigned to PTCA (n=200) or placement of a MultiLink stent (Guidant ACS). Stenting was performed in 16.5% assigned to PTCA, and in 95.6% of patients assigned to stent placement. Vessel size was 2.37±0.27 mm (PTCA group) and 2.41±0.25 mm (stent group; p=ns). In this study, the final minimal lumen diameter achieved was also significantly smaller in the PTCA group (1.98±0.41 mm) than in the stent group (2.35±0.40 mm; p<0.001). At follow-up angiography (available in 83% of patients), the lumen diameter was similar in the two groups (1.28±0.62 and 1.35±0.73 mm, respectively; p=ns), as well as the restenosis rate (37.4 and 35.7%; p=ns).

The BESMART (BeStent in Small Arteries) trial was a French multicenter study¹⁰ , utilizing the BeStent Small (Medtronic) for de-novo lesions in arteries <3 mm by visual estimate. A total of 381 patients were randomized, 189 to PTCA, 192 to stent placement; 22.7% of patients in the PTCA group crossed over to stents, in 1.0% of patients in the stent group no stent was placed. Vessel size was 2.24±0.34 mm in the PTCA group, and 2.23±0.36 mm in the stent group (p=ns). Similar to all other studies, the acute angiographic result was better after stent placement, with a minimal lumen diameter of 1.70±0.46 mm after PTCA compared to 2.06±0.412 mm after stent place­ment (p=0.001). However, this study yielded better results for stent placement after six months, with a significantly lower minimal lumen diameter after PTCA (1.19±0.58 mm vs. 1.43±0.53 mm in the stent group; p=0.0001), and higher restenosis rate (47 vs. 21%, respectively; p=0.0001).

The SISA study (Stenting in Small Arteries) was a multicenter worldwide study performed in 352 patients with de-novo lesions in 2.3 to 2.9 mm vessels^11-13 . The stent used for this trial was also the BeStent (Medtronic). The cross-over rate was low in the stent arm (3.0%), but high in the PTCA arm (20.9%). The reference diameters were 2.45±0.34 mm (PTCA) and 2.50±0.37 mm (stent; p=ns). In parallel to the other studies, the acute minimal lumen diameter achieved was smaller after PTCA (1.82 vs. 2.28 mm in the stent group). After six months, the minimal lumen diameter was similar in both groups (1.38±0.56 and 1.44±0.53 mm, respectively; p=ns), with no sig­nificant difference in restenosis rates (32.4 and 28.0%).

The RAP study (Restenosis en Arterias Pequeñas) was performed in several centers in Spain¹⁴ , comparing PTCA with stent implantation in de-novo lesions (vessel size 2.2 to 2.7 mm) in 426 patients. Like BESMART and SISA, this study was performed with the small BeStent (Medtronic). Vessel size was 2.29±0.39 mm (PTCA) and 2.32±0.32 mm (stent; p=ns). The final lumen diameter was 1.84±0.62 mm and 2.33±0.86 mm, respectively (p<0.01). After six months, there was still a significant difference in lumen diameter (1.31±0.58 mm vs. 1.47±0.50 mm; p=0.01), with a sig­nificant difference in restenosis rates (37 vs. 27%; p<0.05).

Two additional randomized trials have to be interpreted with caution as both were stopped prematurely by the sponsors.

The CORDIS-MICA trial was performed in several centers in the US, utilizing the MiniCrown stent (Cordis)¹⁵ . With 600 patients initially mandated by the protocol, the trial was stopped by the sponsor after randomization of 128 patients. The trial had a very high cross-over rate of 37% in the PTCA arm. Like other studies, the acute angiographic results were inferior in the PTCA arm (p<0.001). Based on a very low number of repeat angiographies mainly driven by repeat symptoms, restenosis rates were high but not significantly different (63 vs. 61%).

The SISCA trial (Stenting in Small Coronary Arteries) was a multicenter trial with the heparin-coated BeStent (Medtronic) performed in Norway and Sweden¹⁶ . The study was terminated by the sponsor after inclusion of 145 of initially 200 planned patients. With a significant difference in the acute final lumen diameter (1.79 vs. 2.22 mm; p<0.001), results after six months were not significantly different (minimal lumen diameter, 1.57 vs. 1.69 mm; restenosis rate, 19 vs. 10%).

 How should these conflicting results be interpreted ?

 Detail angiographic data from all trials are summarized in Table 1 for direct compari­son. Although a significant difference in the rate of angiographic restenosis had been observed in only two studies (BESMART and RAP), the restenosis rate in the PTCA arm was higher in all trials except for the study of Park et al.. To analyze this trend in favor of routine stenting further, we calculated the relative risk for angiographic restenosis using all data from all seven studies: this was highly significant with 0.74 (95% confidence interval, 0.66 - 0.83; p<0.001). However, several differences between these studies and specific aspects outlined below qualify the primary conclusion from this cumulative analysis.

Most important, acute final results achieved were inferior in the PTCA group as com­pared to the stent group in all studies. The smallest differences in final %-diameter stenosis between the PTCA and the stent arm were observed in the Park study and ISAR-SMART, the highest in SISA and SISCA. Suboptimal results after PTCA are an independent predictor of restenosis⁵ . The highest discrepancies between acute angio­graphic results could be observed in the PTCA groups, ranging from 13.7 to 29%. This difference between studies might partially be responsible for differences in late angio­graphic outcome. Figure 1 illustrates the absolute difference in restenosis rates between the stent and PTCA arm of each study as a function of the final %-diameter stenosis achieved in the PTCA arm. There is a clear linear relationship (r=0.88), signi­fying that a positive effect of stenting was only observed in the presence of poor acute results in the PTCA arm. In large vessels, suboptimal results after PTCA are a valid indication for stent placement¹⁷ . Furthermore, studies on provisional stenting versus routine stenting in large vessels have suggested that the benefit of routine stent place­ment diminishes if PTCA yielded optimal angiographic results^18-23 . Such a relationship is clearly present in small vessels, as illustrated by Figure 1.Stent design is known to influence restenosis development^24-26 , and these trials were performed with several different stent types. The study by Park et al. with the 7-cell NIR stent, ISAR-SMART with ACS MultiLink, BESMART, SISA, RAP and SISCA with the BeStent for small vessels, and CORDIS-MICA with the MiniCrown stent. In a randomized comparison of five different stent designs including the MultiLink, NIR and Palmaz-Schatz stents, we found a significant difference in event-free survival after one year²⁵ . In this unselected patient population (mean vessel size of 3.00 mm), the lowest restenosis rate was observed for the MultiLink (25.3%), the highest for the NIR stent (35.0%). These rates are lower than the respective rates of the stent arms of ISAR-SMART (35.7%) and the study of Park et al. (35.7%) which is consistent with known increasing risk for restenosis with decreasing vessel size^4,6 . The data from BESMART, SISA, RAP and SISCA indicate lower restenosis rates for the BeStent in comparison to the other studies with other stent types. There is only few data available from other trials for the BeStent. One small observational study in an unselected study population found a restenosis rate of 27%²⁷ . Moer et al. reported on a small ran­domized trial comparing the BeStent to the 7-cell NIR stent in small coronary arteries²⁸ . They found a restenosis rate of 22.5% with no significant differences between the BeStent and NIR. This rate is comparable to the rates for the BeStent from BESMART, SISA and RAP, but not with the rate for the NIR stent in the study by Park et al. which was 35.7%. This indicates that the absolute differences in restenosis rates between the different stent types in different studies have to be interpreted with caution, and do not allow for a direct comparison.

Most of the trials used “dedicated” small vessel stents, (except ISAR-SMART with the MultiLink). These stents have fewer struts, cells or loops per circumference than large-vessel stents, and/or have thinner stent struts to reduce the metal coverage and load relative to the circumferential vessel wall. This practical approach however, has not been validated in dedicated clinical trials. In contrary, there are data indicating that less coverage might lead to higher restenosis rates: Garasic et al. have found that neointimal thickness is higher for stents with eight struts per cross section as compared to stents with 12 struts per cross section in an experimental setting²⁹ . Thinner struts on the other hand, have been associated with a lower restenosis rate: in a randomized trial with 651 patients, a significantly lower restenosis rate (15.0%) was found for a thin-strut stent (ACS MultiLink; strut thickness 50 mm) in comparison to a thick-strut stent (25.8%; p=.003), the MultiLink Duet (140 mm)³⁰ ; other than strut thickness, these two stents are almost identical in design. Strut thickness has an influence on mechanical strength, and radial force of different stents has been found to vary considerably³¹ . Furthermore, different mechanical characteristics may lead to differences in elastic recoil after deployment³² . As geometric configuration of stents and vascular injury determine restenosis development³³ , further studies are needed to fully evaluate all modifications of mechanical characteristics of stents on vessel trauma and restenosis development in small vessels.

The risk for restenosis increases with decreasing vessel size^4,6 . Mean vessel size in the studies mentioned above was in the range of 2.23 to 2.69 mm. However, from these mean values there is no detectable trend for increasing restenosis. For example, one of the lowest restenosis rates were reported for the study with the smallest mean vessel size (BESMART). Intravascular ultrasound (IVUS) imaging has provided additional information on vessel size and dimensions. Frequently, the extent of coronary artery disease by angiography and IVUS are discrepant³⁴ with angiography underestimating the magnitude of disease. IVUS measurements of vessel size and final lumen dimen­sions have been found to be powerful predictors of angiographic restenosis³⁵ . Further­more, IVUS measurements have indicated that true vessel size may be underestimated, ie, “small” vessels by angiography are frequently diffusely diseased “large” vessels. Okabe at al. have further elucidated this relationship³⁶ : 176 patients with stent place­ment were divided into three groups according to angiographic and IVUS measure­ments: I, large vessels by angiography (³2.5 mm), II, small by angiography (<2.5 mm), but large by IVUS (³4 mm), and III, small by angiography and IVUS (<4.0 mm). Interestingly, restenosis rates were not significantly different between group I and II (25.9 and 24.0%, respectively), but significantly higher in group III (66.7%, p<.05 in comparison to either I or II)³⁶ . It can be hypothesized that vessel trauma was greater in group III than in group II, leading to more neointimal hyper­plasia. None of the randomized trials in Table 1 utilized IVUS measurements; there­fore their diverging data cannot be explained by this hypothesis. Additional studies are needed to further elucidate these findings.

Suboptimal PTCA results are an established indication for stent placement in larger vessels. The cross-over rate in the PTCA arm of the studies listed in Table 1 was in the range of 14 to 23% (only exception CORDIS-MICA with 37%). These rates are higher than in the earlier trials of BENESTENT (5.1%)¹ and STRESS (6.9%)² , but lower than in trials comparing strategies of optimal PTCA with elective stenting (37 to 51%)^22,23 . Therefore, the practice in these studies reflect a comparison of systematic stenting versus PTCA with stents only for suboptimal results rather than systematic stenting versus plain PTCA. The reasons for cross-over from PTCA to stent placement in these studies are not available in detail. However, typical reasons are suboptimal angiographic results, such as residual lumen narrowing >50% and large dissections. Residual dissections are a strong predictor of major cardiac complications during the early course^37,38 , and to a lesser degree, final lumen diameter³⁸ . Several multivariate analyses for the risk of early adverse cardiac events or stent thrombosis during the first 30 days have not been able to identify vessel size or reference diameter as an indepen­dent predictor^37-39 ; however, in most of these studies there is a trend for higher event rates by univariate analysis or in direct comparisons of small with large vessels^4,7 . For studies comparing stenting with PTCA as listed in Table 1, clinical event rates after 30 days are not available except for ISAR-SMART and SISCA. In both trials, no statisti­cally significant difference was found: in ISAR-SMART, the event rate was 2.9% in the stent arm, and 1.5% in the PTCA arm, in SISCA, the rates were 3.9 and 8.8%, respectively.

ISAR-SMART is the only study with systematic use of glycoprotein IIb/IIIa inhibitors in both arms. Results from various studies on the use glycoprotein IIb/IIIa inhibitors during coronary interventions have yielded inconsistent results with respect to the effect on angiographic restenosis⁴⁰ , and there are no data indicating a contrasting effect on restenosis after PTCA versus stent placement. Therefore, differences in the use of glycoprotein IIb/IIIa inhibitors cannot account for the conflicting results of the trials in Table 1 with respect to restenosis. However, it appears that the low 30-day clinical event rate of ISAR-SMART in comparison with SISCA (see above) could be well explained by the systematic use glycoprotein IIb/IIIa inhibitors in ISAR-SMART.

Table 1 - Angiographic Data from Randomized Trials

Figura 1. This graph illustrates the correlation of the difference in restenosis rates (data for PTCA arm - data for stent arm) with the final %-diameter stenosis achieved in the PTCA arm at the end of the procedure. Each data point represents one of the study listed in Table 1: 1, Park et al.; 2, ISAR-SMART; 3, BESMART; 4, SISA; 5, RAP; 6, SISCA; 7, CORDIS-MICA. There is a clear linear correlation (r=0.88), suggesting that a benefit of systematic stenting in randomized small vessel trials was only present if procedures in the PTCA arm were finished with suboptimal final results.

Available data from randomized trials on stenting versus PTCA in small vessels do not corroborate a general strategy of systematic stent placement in small vessels, despite the fact that cumulative data suggest a significant benefit. However, this advantage is clearly dependent on the final result achieved with plain PTCA. Plain balloon angioplasty is clearly inferior if finished suboptimally, as illustrated in Figure 1. It is notable that a strategy of plain PTCA required stent placement in 10-20% of patients due to suboptimal angiographic results after balloon angioplasty in all studies. Conse­quently, provisional stenting after an aggressive attempt to achieve a good result with plain ballon angioplasty seems warranted.

1.     Serruys PW, de Jaegere P, Kiemeneij F, Macaya C, Rutsch W, Heyndrickx G, Emanuelsson H, Marco J, Legrand V, Materne P, et al. A comparison of bal­loon-expandable-stent implantation with balloon angioplasty in patients with coronary artery disease. N Engl J Med. 1994;331:489-95.

2.     Fischman DL, Leon MB, Baim DS, Schatz RA, Savage MP, Penn I, Detre K, Veltri L, Ricci D, Nobuyoshi M, 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.

3.     Pepine CJ, Holmes DR, et.al. ACC Expert Consensus Document:  Coronary Artery Stents. J Am Coll Cardiol. 1996;28:782-794.

4.     Elezi S, Kastrati A, Neumann FJ, Hadamitzky M, Dirschinger J, Schömig A. Vessel size and long-term outcome after coronary stent placement. Circulation. 1998;98:1875-80.

5.     Hirshfeld JW, Schwartz JS, Jugo R, MacDonald RG, Goldberg S, Savage MP, Bass TA, Vetrovec G, Cowley M, Taussig AS, Whitworth HB, Margolis JR, Hill JA, Pepine CJ. Restenosis after coronary angioplasty:  A multivariate sta­tistical model to relate lesion and procedure variables to restenosis. J Am Coll Cardiol. 1991;18:647-656.

6.     Foley DP, Melkert R, Serruys PW. Influence of coronary vessel size on renar­rowing process and late angiographic outcome after successful balloon angio­plasty. Circulation. 1994;90:1239-51.

7.     Akiyama T, Moussa I, Reimers B, Ferraro M, Kobayashi Y, Blengino S, Di Francesco L, Finci L, Di Mario C, Colombo A. Angiographic and clinical out­come following coronary stenting of small vessels: a comparison with coronary stenting of large vessels. J Am Coll Cardiol. 1998;32:1610-8.

8.     Park SW, Lee CW, Hong MK, Kim JJ, Cho GY, Nah DY, Park SJ. Randomized comparison of coronary stenting with optimal balloon angioplasty for treatment of lesions in small coronary arteries. Eur Heart J. 2000;21:1785-1789.

9.     Kastrati A, Schömig A, Dirschinger J, Mehilli J, Dotzer F, von Welser N, Neumann FJ. A randomized trial comparing stenting with balloon angioplasty in small vessels in patients with symptomatic coronary artery disease. ISAR- SMART Study Investigators. Intracoronary Stenting or Angioplasty for Restenosis Reduction in Small Arteries. Circulation. 2000;102:2593-8.

10.   Kleiman NS, Califf RM. Results from late-breaking clinical trial sessions at ACCIS 2000 and ACC 2000. J Am Coll Cardiol. 2000;2000:310-325.

11.   Schalij MJ, Doucet S, Hilton D, Vrolix M, DeBruyne B, Bilodeau L, Udaychalerm W, Chenu P. The SISA Study: a randomized comparison of bal­loon angioplasty and stent to prevent restenosis in small arteries: 6 month angiographic and 12 month clinical outcome (abstract). Circulation. 2000;102:II-663.

12.   Schalij MJ, Doucet S, Bilodeau L, Reiber JHC, Hilton DJ, Vrolix MC. The Stenting in Small Arteries Study (SISA): quantitative angiographic results per segment treated (abstract). J Am Coll Cardiol. 2001;37:52A.

13.   Doucet S, Schalig MJ, Hilton D, Vrolix M, DeBruyne B, Chenu P, Bilodeau L, Udaychalerm W. The SISA Study: a randomized comparison of balloon angio­plasty and stent to prevent restenosis in small arteries (abstract). J Am Coll Cardiol. 2000;35:8A.

14.   Garcia E, Gomez-Recio M, Moreno R, Pasalodos J, Bethancourt A, Zueco J, Iniguez A. Stent reduces restenosis in small vessels: results of the RAP Study (abstract). J Am Coll Cardiol. 2001;37:17A.

15.   Savage MP, Fischman DL, Kada F, Fry ETA, Kiernan FJ, Goldberg SL. A ran­domized comparison of elective stenting and balloon angioplasty in the treat­ment of small coronary arteries (abstract). Circulation. 1999;100:I-503.

16.   Moer R, Myreng Y, Albertsson P, Gunnes P, Lindvall B, Wiseth R, Molstad P, Ytre-Arne K, Golf S. Stenting in Small Coronary Arteries (SISCA): a random­ized comparison of heparin coated beStent and balloon angioplasty (abstract). J Am Coll Cardiol. 2001;37:46A-47A.

17.   Pepine CJ, Holmes DR, Jr. Coronary artery stents. American College of Cardiology. J Am Coll Cardiol. 1996;28:782-94.

18.   Rodriguez A, Ayala F, Bernardi V, Santaera O, Marchand E, Pardinas C, Mauvecin C, Vogel D, Harrell LC, Palacios IF. Optimal coronary balloon angioplasty with provisional stenting versus primary stent (OCBAS): imme­diate and long-term follow-up results. J Am Coll Cardiol. 1998;32:1351-7.

19.   Weaver WD, Reisman MA, Griffin JJ, Buller CE, Leimgruber PP, Henry T, D'Haem C, Clark VL, Martin JS, Cohen DJ, Neil N, Every NR. Optimum percutaneous transluminal coronary angioplasty compared with routine stent strategy trial (OPUS-1): a randomised trial. Lancet. 2000;355:2199-203.

20.   Di Mario C, Moses JW, Anderson TJ, Bonan R, Muramatsu T, Jain AC, Suarez de Lezo J, Cho SY, Kern M, Meredith IT, Cohen D, Moussa I, Colombo A. Randomized comparison of elective stent implantation and coronary balloon angioplasty guided by online quantitative angiography and intracoronary Dop­pler. DESTINI Study Group (Doppler Endpoint STenting INternational Investi­gation). Circulation. 2000;102:2938-44.

21.   Serruys PW, de Bruyne B, Carlier S, Sousa JE, Piek J, Muramatsu T, Vrints C, Probst P, Seabra-Gomes R, Simpson I, Voudris V, Gurne O, Pijls N, Belardi J, van Es GA, Boersma E, Morel MA, van Hout B. Randomized comparison of primary stenting and provisional balloon angioplasty guided by flow velocity measurement. Doppler Endpoints Balloon Angioplasty Trial Europe (DEBATE) II Study Group. Circulation. 2000;102:2930-7.

22.   Anderson HV, Carabello BA. Provisional versus routine stenting: routine stenting is here to stay. Circulation. 2000;102:2910-4.

23.   Cantor WJ, Peterson ED, Popma JJ, Zidar JP, Sketch MH, Jr., Tcheng JE, Ohman EM. Provisional stenting strategies: systematic overview and impli­cations for clinical decision-making. J Am Coll Cardiol. 2000;36:1142-51.

24.   Kastrati A, Mehilli J, Dirschinger J, Pache J, Ulm K, Schühlen H, Seyfarth M, Schmitt C, Blasini R, Neumann FJ, Schömig A. Restenosis after coronary placement of various stent types. Am J Cardiol. 2001;87:34-39.

25.   Kastrati A, Dirschinger J, Boekstegers P, Elezi S, Schühlen H, Pache J, Steinbeck G, Schmitt C, Ulm K, Neumann FJ, Schömig A. Influence of stent design on 1-year outcome after coronary stent placement: a randomized comparison of five stent types in 1,147 unselected patients. Catheter Cardiovasc Interv. 2000;50:290-7.

26.   Edelman ER, Rogers C. Stent-versus-stent equivalency trials : are some stents more equal than others? Circulation. 1999;100:896-8.

27.   Lau KW, Ding ZP, Johan A, Hung JS. Mid-term clinical and angiographic follow-up outcome after placement of a new balloon expandable stent in native coronary arteries. Catheter Cardiovasc Interv. 2000;49:348-51.

28.   Moer R, Myreng Y, Molstad P, Ytre-Arne K, Sirnes PA, Golf S. Stenting small coronary arteries using two second-generation slotted tube stents: acute and six-month clinical and angiographic results. Catheter Cardiovasc Interv. 2000;50:307-13.

29.   Garasic JM, Edelman ER, Squire JC, Seifert P, Williams MS, Rogers C. Stent and artery geometry determine intimal thickening independent of arterial injury. Circulation. 2000;101:812-8.

30.   Kastrati A, Mehilli J, Dirschinger J, Dotzer F, Schühlen H, Neumann FJ, Fleckenstein M, Pfafferoth C, Seyfarth M, Schömig A. Intracoronary Stenting and Angiographic Results: Strut Thickness Effect on Restenosis Outcome (ISAR-STEREO) Trial. Circulation. 2001;103:2816-2821.

31.   Rieu R, Barragan P, Masson C, Fuseri J, Garitey V, Silvestri M, Roquebert P, Sainsous J. Radial force of coronary stents: a comparative analysis. Catheter Cardiovasc Interv. 1999;46:380-91.

32.   Barragan P, Rieu R, Garitey V, Roquebert PO, Sainsous J, Silvestri M, Bayet G. Elastic recoil of coronary stents: a comparative analysis. Catheter Cardiovasc Interv. 2000;50:112-9.

33.   Rogers C, Edelman ER. Endovascular stent design dictates experimental restenosis and thrombosis. Circulation. 1995;91:2995-3001.

34.   Nissen SE, Yock P. Intravascular ultrasound: novel pathophysiological insights and current clinical applications. Circulation. 2001;103:604-16.

35.   Mintz GS, Popma JJ, Pichard AD, Kent KM, Satler LF, Chuang YC, Griffin J, Leon MB. Intravascular ultrasound predictors of restenosis after percutaneous transcatheter coronary revascularization. J Am Coll Cardiol. 1996;27:1678-1692.

36.   Okabe T, Asakura Y, Ishikawa S, Asakura K, Mitamura H, Ogawa S. Determin­ing appropriate small vessels for stenting by intravascular ultrasound. J Invasive Cardiol. 2000;12:631-632.

37.   Schühlen H, Kastrati A, Dirschinger J, Hausleiter J, Elezi S, Wehinger A, Pache J, Hadamitzky M, Schömig A. Intracoronary stenting and risk for major adverse cardiac events during the first month. Circulation. 1998;98:104-111.

38.   Cutlip DE, Baim DS, Ho KK, Popma JJ, Lansky AJ, Cohen DJ, Carrozza JP, Jr., Chauhan MS, Rodriguez O, Kuntz RE. Stent thrombosis in the modern era: a pooled analysis of multicenter coronary stent clinical trials. Circulation. 2001;103:1967-71.

39.   Moussa I, Di Mario C, Reimers B, Akiyama T, Tobis J, Colombo A. Subacute stent thrombosis in the era of intravascular ultrasound-guided coronary stenting without anticoagulation: frequency, predictors and clinical outcome. J Am Coll Cardiol. 1997;29:6-12.