Stent Placement to Prevent Restenosis After Angioplasty in Small Coronary Arteries

Coronary stenting versus balloon angioplasty in small vessels

OBJECTIVES

A meta-analysis of 11 randomized trials was done to compare stenting versus balloon angioplasty (BA) in small coronary vessels.

BACKGROUND

Randomized studies on coronary stenting (CS) in small vessels have yielded controversial results.

METHODS

Eleven randomized trials on CS versus BA in small vessels, including angiographic re-evaluation at six months, were analyzed.

RESULTS

The BeStent (Medtronic Instent, Minneapolis, Minnesota) was used in four studies, the Multi-Link (Guidant, Advanced Cardiovascular Systems Inc., Santa Clara, California) in three trials, and the NIR (Boston Scientific Corp., Boston, Massachusetts), JoStent (Jomed International AB, Helsingborg, Sweden), Tenax (Biotronik, Berlin, Germany), and BioDivysio (Abbott Vascular Devices, Redwood City, California) in the remaining four trials. Overall, 3,541 patients were included (1,672 allocated to BA and 1,869 to stent). The rate of cross-over from balloon to stent in the pooled population was 19%, and unsuccessful stent deployment occurred in 2% of the patients allocated to stent. The pooled rates of restenosis were 25.8% and 34.2% in patients allocated to stent and balloon, respectively (p = 0.003) (risk ratio [RR] 0.77; 95% confidence interval [CI] 0.65 to 0.92). A smaller reference vessel diameter at baseline was associated with a higher risk reduction in the restenosis rate (y = -3.551 + 1.826 [x]; p = 0.012). Patients allocated to stent had lower rates of major adverse cardiac events (15.0% vs. 21.8%, p = 0.002; RR 0.70; 95% CI 0.57 to 0.87) and new target vessel revascularizations (12.5% vs. 17.0%, p = 0.004; RR 0.75, 95% CI 0.61 to 0.91).

CONCLUSIONS

Elective stenting is superior to provisional stenting in small coronary arteries. This benefit is more evident in smaller coronary arteries.

Randomized comparison of balloon angioplasty versus silicon carbon-coated stent implantation for de novo lesions in small coronary arteries

The objectives of this study were to compare the short- and long-term clinical and angiographic outcomes of conventional balloon angioplasty versus elective silicon carbide-coated stent implantation in de novo lesions in small coronary arteries (<3.0 mm). Angioplasty of small coronary arteries is associated with high restenosis rates. The beneficial effects of stent implantation on restenosis rates and clinical outcomes have been suggested by observational studies. However, randomized trials comparing balloon angioplasty with stenting show conflicting results. A total of 496 patients with a de novo stenosis in a coronary artery, with a diameter between 2.0 and 3.0 mm, were randomly assigned to balloon angioplasty (n = 246) or stent implantation (n = 250). One-year clinical and 6-month angiographic follow-up were performed. Baseline characteristics were similar for the 2 groups, with 16% having diabetes and 77% complex lesions (type B or C). Crossover to stents occurred in 29% of patients randomized to balloon angioplasty. At 6 months, angiographic restenosis rates were 25% versus 21% for the angioplasty and stent groups, respectively (p = NS). One-year clinical follow-up showed no difference in occurrence of major adverse cardiac events. Elective silicon carbon-coated stent implantation in small coronary arteries is safe and effective, with no beneficial effect on angiographic or clinical outcome compared with balloon angioplasty with provisional stenting.

Treatment of very small vessels with 2.25-mm diameter sirolimus-eluting stents (from the RESEARCH registry)

A total of 91 patients with 112 lesions received 2.25-mm sirolimus-eluting stents (SESs), and these lesions were compared with those treated with SESs of > or =2.5-mm diameter in the same procedure (n = 109). The reference diameters were 1.88 +/- 0.34 and 2.52 +/- 0.57 mm, respectively (p <0.01). At follow-up, the late lumen loss was 0.07 +/- 0.48 mm for the 2.25-mm SES versus 0.03 +/- 0.38 mm for the larger SES (p = 0.5), and the binary restenosis rate was 10.7% versus 3.9%, respectively (p = 0.1). The 12-month target lesion revascularization rate was 5.5%. In conclusion, 2.25-mm SESs were associated with low rates of clinical and angiographic late complications.

Effect of stents in reducing restenosis in small coronary arteries: A meta-analysis

The ability of stents to reduce restenosis was established in larger coronary arteries. Clinical trials of stenting in smaller vessels have yielded conflicting results due in part to their sample sizes. The aim of this meta-analysis was to increase the statistical power by pooling data from these clinical trials. Trials were identified from Medline search, review of recent cardiology meetings' abstracts, and manual review of bibliographies. Studies were included if they were prospective randomized controlled trials. Endpoints examined included a dichotomized definition of angiographic restenosis, target lesion revascularization (TLR), target vessel revascularization (TVR), or any repeat revascularization. Pooling of data was performed by calculating a Mantel-Haenszel odds ratio (OR). The analysis included 2,598 patients enrolled in eight clinical trials. Stenting significantly reduced restenosis (OR = 0.62; 95% CI = 0.61-0.63). Concordantly, stenting reduced TLR (OR = 0.49), TVR (OR = 0.90), and any revascularization (OR = 0.48). This meta-analysis supports the hypothesis that stenting reduces restenosis in small coronary arteries as well as in larger coronary arteries. The apparent discordant result of individual clinical trials was due in part to underpowering related to small sample sizes.

Balloon angioplasty plus cilostazol administration versus primary stenting of small coronary artery disease: Final results of COMPASS

Efficacy of primary stenting in small coronary artery disease is still controversial. Cilostazol has been reported to control restenosis after balloon angioplasty (BA). The aim was to compare primary stenting with BA plus cilostazol administration in small coronary artery disease. Of 106 lesions located in small coronary artery (reference < 3.0 mm), 50 lesions were randomly assigned to the stenting and 56 lesions to the BA-cilostazol group. Multilink stent was implanted in the stenting group. In the BA-cilostazol group, cilostazol (200 mg/day) without aspirin was administered for 6 months after BA. Ticlopidine was given for 1 month when bailout stent was implanted. Serial quantitative angiography was performed at the procedure and 6 months. The primary endpoint was 6-month angiographic restenosis. Clinical event rates at 1 year were also assessed. Baseline characteristics were similar. All procedures were successful. Bailout stenting was performed in three lesions in the BA-cilostazol group. No side effects of cilostazol were observed. Postprocedural lumen diameter was significantly larger (2.69 vs. 2.03 mm; P < 0.0001) in the stenting group. However, the follow-up lumen diameter was not different (1.76 vs. 1.85 mm, stenting vs. BA-cilostazol). Although the difference was not statistically significant, restenosis rate was lower in the BA-cilostazol group (13.2% vs. 24.5%; P = 0.11). Subacute thrombosis occurred in one patient and target revascularization rate was higher in the stenting group (22.0% vs. 10.7%; P = 0.10). BA plus cilostazol administration seems to be a favorable strategy for small coronary artery disease.

Predictors of Restenosis After Implantation of 2.5 mm Stents in Small Coronary Arteries

BACKGROUND

The results of stent implantation for small coronary disease have been inconclusive. The purpose of the present study was to evaluate the factors in predicting the risk of angiographic restenosis after 2.5-mm stent implantation for small coronary arteries.

METHODS AND RESULTS

The study group comprised 134 consecutive patients who had a reference small coronary artery with diameter from 1.8 mm to 2.5 mm on quantitative coronary angiography and who had been successfully treated by stent implantation with a 2.5-mm stent. Of the 134 patients, 55 had angiographic restenosis (41%). The rate of target lesion revascularization was 32%. Diabetes mellitus, acute coronary syndrome, lesion length, bifurcation lesion, lower left ventricular ejection fraction (LVEF), stent strut, stent/artery ratio, and stent length were identified as predictors of restenosis by univariate analysis. Subsequent multivariate analysis revealed that lower LVEF (odds ratio (OR) 3.37, p=0.01), bifurcation lesion (OR 2.47, p=0.04), thicker stent strut (OR 2.30, p=0.04), and longer stent length (OR 1.05, p=0.02) were significant predictors of restenosis.

CONCLUSIONS

Two pre-interventional factors (reduced left ventricular function and bifurcated lesion) and 2 procedure-related factors (thickness of stent strut and total stent length) were identified as predictors of restenosis. These factors should be taken into account when deciding on the percutaneous coronary intervention strategy for small coronary artery disease.

Effectiveness of stents in small coronary arteries

This study was prospectively randomized to assess the efficacy and safety of Jo heparin-coated stent deployment in small vessels compared with balloon angioplasty. In 202 patients, restenosis in balloon and stent arms was 49% and 30%, respectively.

Comparison of rotational atherectomy with conventional balloon angioplasty in the prevention of restenosis of small coronary arteries: results of the Dilatation vs Ablation Revascularization Trial Targeting Restenosis (DART)

BACKGROUND

The optimum treatment of obstructive coronary disease in small (<3.0 mm diameter) arteries remains unknown. Rotational atherectomy is an approved treatment that might reduce the vascular injury during percutaneous coronary intervention compared with angioplasty. We report on a multicenter, randomized, blinded end point trial comparing rotational atherectomy with balloon angioplasty in the prevention of restenosis of obstructed small coronary arteries.

METHODS

A total of 446 patients with myocardial ischemia associated with an angiographic stenosis in a native coronary artery 2 to 3 mm in diameter and < or =20 mm in length without severe calcification were randomly assigned to receive rotational atherectomy (n = 227) or balloon angioplasty (n = 219). The primary end point was target vessel failure at 12 months (defined as the composite of death, Q-wave myocardial infarction, and clinically driven repeat revascularization of the target vessel).

RESULTS

The mean reference vessel diameter was 2.46 +/- 0.40 mm, the mean lesion length was 9.97 +/- 5.59 mm, and the prevalence of diabetes mellitus was 32%. Acute procedural success (91.6% for rotational atherectomy, 94.1% for balloon angioplasty, P =.36) and target vessel failure at 12 months were not significantly different (30.5% vs 31.2%, P =.98). At 8 months, there were no significant differences in minimum lumen diameter (1.28 +/- 0.63 mm vs 1.19 +/- 0.54 mm, P =.26), percent diameter stenosis (28% +/- 12% vs 29% +/- 15%, P =.59), binary restenosis rate (50.5% vs 50.5%, P = 1.0), or late loss index (0.57 vs 0.62, P =.7). No Q-wave myocardial infarctions occurred in either arm of the study, and non-Q-wave myocardial infarctions (defined as creatine kinase level >2 times normal with an elevated creatine kinase-myocardial band isoenzyme level) occurred in 2.2% and 1.4% of the patients in the rotational atherectomy and balloon angioplasty groups, respectively (P =.72).

CONCLUSION

Rotational atherectomy was found to be safe in the treatment of obstructed small arteries, but lower rates of target vessel failure were not achieved compared with balloon angioplasty. Because the acute gain and loss index ratios of the 2 treatments were similar, there was no evident beneficial antirestenosis mechanism seen for rotational atherectomy.

Heparin-coated stent placement for the treatment of stenoses in small coronary arteries of symptomatic patients

BACKGROUND

The role of stents, especially of heparin-coated stents for the treatment of stenoses in small coronary arteries, is still unclear. Therefore, we performed this prospective, randomized trial to evaluate the angiographic and clinical outcome after treatment of stenoses in small coronary arteries (2.0 to 2.6 mm) of symptomatic patients.

METHODS AND RESULTS

We randomly assigned 588 patients to angioplasty (n=195), bare stenting (n=196), or heparin-coated stenting (n=197). The primary end point was minimal lumen diameter (MLD) at 6 months. With comparable baseline parameters, the two stent arms showed a larger postinterventional MLD, larger acute gain, and smaller residual percent diameter stenosis, although a residual stenosis of 12+/-16% was achieved in the angioplasty arm, including a 27% crossover rate to stenting. Eighty percent of patients had follow-up angiography, which documented a borderline significantly larger MLD and smaller percent diameter stenosis for the two stent groups (1.34+/-0.48 mm and 42+/-20% after angioplasty, 1.47+/-0.48 mm and 36+/-20% after bare stenting, and 1.45+/-0.54 mm and 38+/-23% after heparin-coated stenting; P=0.049 and P=0.038, respectively), but restenosis rates were not different (32%, 25%, and 30%). Thrombotic events occurred in 1.0% after angioplasty and 0.5% after bare or heparin-coated stenting. Survival without myocardial infarction or target vessel revascularization at 250 days was 84.6% (angioplasty), 88.3% (bare stenting), and 88.3% (heparin-coated stenting; log-rank P=0.39).

CONCLUSION

Compared with angioplasty with provisional stenting, bare and heparin-coated stenting confer superior angiographic results and a nonsignificant 24% reduction in clinical events, with no difference between bare and heparin-coated stenting in the treatment of stenoses in small coronary arteries.

Angiographic findings of the multicenter Randomized Study With the Sirolimus-Eluting Bx Velocity Balloon-Expandable Stent (RAVEL): sirolimus-eluting stents inhibit restenosis irrespective of the vessel size

BACKGROUND

Restenosis remains the major limitation of coronary catheter-based intervention. In small vessels, the amount of neointimal tissue is disproportionately greater than the vessel caliber, resulting in higher restenosis rates. In the Randomized Study With the Sirolimus-Eluting Bx Velocity Balloon-Expandable Stent (RAVEL) trial, approximately 40% of the vessels were small (<2.5 mm). The present study evaluates the relationship between angiographic outcome and vessel diameter for sirolimus-eluting stents.

METHODS AND RESULTS

Patients were randomized to receive either an 18-mm bare metal Bx VELOCITY (BS group, n=118), or a sirolimus-eluting Bx VELOCITY stent (SES group, n=120). Subgroups were stratified into tertiles according to their reference diameter (RD; stratum I, RD <2.36 mm; stratum II, RD 2.36 mm to 2.84 mm; stratum III, RD >2.84 mm). At 6-month follow-up, the restenosis rate in the SES group was 0% in all strata (versus 35%, 26%, and 20%, respectively, in the BS group). In-stent late loss was 0.01+/-0.25 versus 0.80+/-0.43 mm in stratum I, 0.01+/-0.38 versus 0.88+/-0.57 mm in stratum II, and -0.06+/-0.35 versus 0.74+/-0.57 mm in stratum III (SES versus BS). In SES, the minimal lumen diameter (MLD) remained unchanged (Delta -0.72 to 0.72 mm) in 97% of the lesions and increased (=late gain, DeltaMLD <-0.72 mm) in 3% of the lesions. Multivariate predictors for late loss were treatment allocation (P<0.001) and postprocedural MLD (P= 0.008).

CONCLUSIONS

Sirolimus-eluting stents prevent neointimal proliferation and late lumen loss irrespective of the vessel diameter. The classic inverse relationship between vessel diameter and restenosis rate was seen in the bare stent group but not in the sirolimus-eluting stent group.

A novel measurement technique to assess the effects of coronary brachytherapy in clinical trials

This paper presents a novel measurement technique to assess the effects of coronary brachytherapy. This new technique is based upon the conventional quantitative coronary analysis (QCA) technique, which is accepted worldwide as an accurate and reliable analysis tool for clinical trials. This paper provides the definitions and main issues important for correct brachytherapy analysis. Based on these definitions, this novel technique is implemented as an extension of conventional QCA software, as a multisegmental analysis tool. It allows to follow the influence of radiation on restenosis, and the mutual relation between intervention devices. A pilot interobserver study was performed to assess the reliability and reproducibility of the brachytherapy analysis tool, using 15 patient cases. The validation results show that the segment lengths, minimum lumen diameter, and reference diameters of the user-defined and derived (sub)segments can be assessed reproducible. However, these good results can only be obtained, when strict and extensive image acquisition and image analysis protocols are followed. From this pilot validation study presented in this paper and only based on a small number of patients, we may conclude that the software can be applied to clinical trials.

Selection of coronary stents

In clinical practice, the operator must decide which stent is most appropriate for the patient. This article focuses on the features of stent design that make a specific stent more or less suitable for a particular type of lesion or anatomy: the "average" coronary lesion, the lesion situated on a curve, the ostial lesion, the bifurcational lesion, the lesion located at the left main stem, the calcified lesion, the chronic total occlusion, the small vessel, the saphenous vein graft, acute or threatened vessel closure, and special situations such as coronary aneurysms and perforations.

Predictive factors for early cardiac events and angiographic restenosis after coronary stent placement in small coronary arteries

OBJECTIVES

The rationale of this study was to identify risk factors that predict early thrombotic events and angiographic restenosis after stenting in small coronary arteries.

BACKGROUND

Rates of cardiac complications and restenosis after percutaneous coronary intervention are higher in patients with small versus large coronary arteries. Because of discordant results, randomized studies comparing stent placement with balloon angioplasty could not establish the best interventional approach to use in this high-risk subset of patients. This study of predictive factors, with special focus on stent design, may provide particular help in this regard.

METHODS

Clinical, lesion-related, and procedural data of a large and unselected population of 3,156 consecutive patients were analyzed in a logistic regression model for both early and late complications. Repeat angiography at six months was performed in 80.8% of eligible patients.

RESULTS

The strongest risk factors for early thrombotic events (cumulative incidence of 4.2%) were the presence of an acute coronary syndrome and reduced left ventricular function. The stent design had no influence on early thrombotic complications. Restenosis (overall rate of 38.4%) was predominantly influenced by procedure-related variables, including the stent design and stented segment length. The incidence of restenosis varied from 29.6% to 55.8%, depending on the stent design used.

CONCLUSIONS

Clinical factors known before the procedure are predominant risk factors for early thrombotic complications, underscoring the need for potent antiplatelet regimens in these patients. In contrast, our findings suggest a major impact of procedural factors, including the choice of stent type, on restenosis.

In-stent restenosis in small coronary arteries: impact of strut thickness

OBJECTIVES; We sought to evaluate whether strut thickness may impact the restenosis rate after stent implantation in small coronary arteries.

BACKGROUND

Small vessel size (<3.0 mm) is an independent risk factor for the occurrence of in-stent restenosis. It has been reported that vessel damage induced during stent deployment is an important factor in restenosis.

METHODS

From our database, we selected all patients who had successful stenting in small native vessels, with angiographic follow-up available, between March 1996 and April 2001. The strut was defined as thin when <0.10 mm and thick when > or = 0.10 mm. According to these criteria, we identified two subgroups: a thin group and a thick group.

RESULTS

A total of 821 (57%) of the 1,447 patients had angiographic follow-up available and were included in the analysis. The thin group included 400 patients with 505 lesions. The thick group included 421 patients with 436 lesions. The restenosis rate was 28.5% in the thin group and 36.6% in the thick group (p = 0.009; odds ratio [OR] 1.44, 95% confidence interval [CI] 1.09 to 1.90). The study group was classified into three subgroups according to the reference vessel diameter: < or = 2.50 mm, 2.51 to 2.75 mm and 2.76 to 2.99 mm. Strut thickness influenced the restenosis rate only in the subgroup with a reference vessel diameter between 2.76 and 2.99 mm, with rates of 23.5% in the thin group and 37% in the thick group (p = 0.006). By logistic regression analysis, predictors of restenosis were stent length (OR 1.03, 95% CI 1.01 to 1.04; p = 0.001), strut thickness (OR 1.68, 95% CI 1.23 to 2.29; p = 0.001) and diabetes mellitus (OR 2.10, 95% CI 1.21 to 3.68; p = 0.007).

CONCLUSIONS

This study supports that strut thickness is an independent predictor of restenosis in coronary arteries with a reference diameter of 2.75 to 2.99 mm.

Coronary artery stents: evaluating new designs for contemporary percutaneous intervention

Intracoronary stents have markedly improved the short- and long-term safety and efficacy of percutaneous coronary intervention by improving acute gains in luminal dimensions, decreasing abrupt vessel occlusion, and reducing restenosis. At present, nearly 90% of all coronary interventions involve stenting. A variety of advances in stent technology and design have expanded the clinical application of stenting to include complex coronary lesions, multivessel disease, and small-diameter vessels. In addition, the development of stents as drug delivery systems for antithrombotic or antiproliferative agents has the potential to expand the role of coronary stenting, and early clinical experience appears promising. The purpose of this review is to describe recent developments in stent design, examine the results of clinical trials of contemporary stents, and present future directions for investigation of new stent technologies.

One core laboratory at two international sites, is that feasible? An inter-core laboratory and intra-observer variability study

To assess the magnitude of differences in QCA outcomes between two cooperating core laboratories in a single trial, we have carried out an inter-core laboratory variability study. Two QCA experts at the Montreal Heart Institute and Heart Core Leiden both analyzed 32 lesions (pre- and post-intervention) in accordance with previously agreed upon standard operating procedures. One of the experts analyzed the whole image set twice to determine the intraobserver variability. The inter-core laboratory differences in the acute gain (n = 31 pairs) are non-significant. The systematic errors of the individual measurements (n = 63 analyses) show an excellent intraclass correlation coefficient of reliability (>75%), except for the stent length (67.7%). The corresponding random errors are small. In general, the intra-observer systematic and random errors are both slightly smaller than those for the inter-core laboratory study. QCA analyses in clinical trials can be carried out in core laboratories at two different locations if and only if highly standardized conditions are maintained.

Twenty-eight-day efficacy and phamacokinetics of the sirolimus-eluting stent

BACKGROUND

In-stent restenosis is caused by neointimal hyperplasia. Sirolimus (rapamycin; Wyeth Research, Radnor, Pennsylvania, USA) inhibits vascular smooth muscle cell proliferation and we evaluated the efficacy of sirolimus in reducing neointimal formation in a rabbit iliac model and in-vivo pharmacokinetics in the porcine coronary model.

DESIGN

Randomized, blinded, prospective animal study.

METHODS

Bilateral rabbit iliac artery stent implantation was performed using crossflex stents (Cordis Corporation, Warren, New Jersey, USA) coated with sirolimus incorporated in a nonerodable polymer. Arteries were randomized to one of four stent groups: uncoated stents (n = 8); polymer control stents (n = 10); low-dose sirolimus-eluting stents (n = 9); and high-dose sirolimus-eluting stents (n = 10). Histomorphometry was performed at 28 days. Arterial tissue and stents were retrieved at 8, 14 and 28 days and blood samples were obtained daily during the first week.

RESULTS

Treatment with low-dose sirolimus was associated with a 23% (P = NS) reduction in neointimal area and treatment with high-dose sirolimus with a 45% (P < 0.05) reduction. Sustained drug release from the stent and prolonged intramural arterial deposition were confirmed for up to 28 days. No detectable sirolimus was found in the blood after 2 days.

CONCLUSION

Controlled-release local delivery of a cell-cycle inhibitor from a nonerodable polymer-coated stent reduced neointimal formation in rabbit iliac arteries in a dose-dependent manner and represents a promising strategy for preventing restenosis.

Clinical benefit of small vessel stenting: one-year follow-up of the SISCA trial

OBJECTIVE

To assess the long-term clinical benefit of elective stenting as compared with percutaneous transluminal coronary angioplasty (PTCA) in small coronary arteries.

DESIGN

The Stenting in Small Coronary Arteries (SISCA) trial was a randomized trial comparing elective stenting with PTCA in coronary arteries with a reference diameter of 2.1-3.0 mm. The heparin-coated beStent was used. Control angiography was performed after 6 months, and the patients were followed clinically for 12 months.

RESULTS

At 6 months the clinical outcome was significantly better in the stent group as compared with the PTCA group, with an event-free survival in 90.5 and 76.1% (p = 0.016), respectively. From 6 to 12 months, event-free survival was unchanged in both groups, demonstrating a sustained long-term clinical benefit of elective stenting.

CONCLUSION

Angioplasty in small coronary arteries is associated with a favorable clinical outcome after 1 year. The clinical benefit of elective stenting using the Hepamed-coated beStent is maintained beyond 6 months, without any tendency towards late events. Thus, elective stenting should be considered as an option when treating small coronary arteries.