Prospective randomized comparison of early and late results of 4 different stent designs

Current understanding of coronary in-stent restenosis. Pathophysiology, clinical presentation, diagnostic work-up, and management

In-stent restenosis is the limiting entity following coronary stent implantation. It is associated with significant morbidity and cost and thus represents a major clinical and economical problem. Worldwide, approximately 250 000 in-stent restenotic lesions per year have to be dealt with. The pathophysiology of instent restenosis is multifactorial and comprises inflammation, smooth muscle cell migration and proliferation and extracellular matrix formation, all mediated by distinct molecular pathways. Instent restenosis has been recognised as very difficult to manage, with a repeat restenosis rate of 50% regardless of the mechanical angioplasty device used. Much more favourable results were reported for the adjunctive irradiation of the in-stent restenotic lesion, with a consistent reduction of the incidence of repeat in-stent restenosis by 50%. Data from the first clinical trials on drug-eluting stents for the treatment of in-stent restenosis have shown very much promise yielding this strategy likely to become the treatment of choice. This review outlines the histological and molecular findings of the pathophysiology, the epidemiology, the predictors and the diagnostic work-up of in-stent restenosis and puts emphasis on the various treatment options for its prevention and therapy.

Robustness of late lumen loss in discriminating drug-eluting stents across variable observational and randomized trials

BACKGROUND

Binary angiographic and clinical restenosis rates can vary widely between clinical studies, even for the same stent, influenced heavily by case-mix covariates that differ among observational and randomized trials intended to assess a given stent system. We hypothesized that mean in-stent late loss might be a more stable estimator of restenosis propensity across such studies.

METHODS AND RESULTS

In 46 trials of drug-eluting and bare-metal stenting, increasing mean late loss was associated with higher target lesion revascularization (TLR) rates (P<0.001). When the class of bare-metal stents was compared with the class of effective drug-eluting stents, late loss was more discriminating than TLR as measured by the high intraclass correlation coefficient (rho) (late loss, rho=0.71 versus TLR, rho=0.22; 95% CI of difference=0.33, 0.65). When the individual drug-eluting stents and bare-metal stents were compared, late loss was a better discriminator than TLR (0.68 versus 0.19; 95% CI of difference=0.24, 0.60). Greater adjustments of study covariates are needed to stabilize assessments of TLR compared with late loss because of greater influence of reference vessel diameter on TLR than on in-stent late loss. Optimization of late loss with the use of a novel method of standardization according to diabetes prevalence and mean lesion length resulted in minor adjustments in late loss (<0.08 mm for 90% of reported trials) and an ordered array of mean late loss values for the stent systems studied.

CONCLUSIONS

Late loss is more reliable than restenosis rates for discriminating restenosis propensity between new drug-eluting stent platforms across studies and might be the optimum end point for evaluating drug-eluting stents in early, nonrandomized studies.

Impact of Carbon Coating on the Restenosis Rate After Stenting of Atherosclerotic Renal Artery Stenosis

PURPOSE

To investigate the impact of carbofilm coating and low-profile rapid exchange stent devices on the restenosis rate after stent-angioplasty of atherosclerotic renal artery stenosis (RAS).

METHODS

During a 2-year period (7/2002-7/2004), 143 consecutive patients with 179 primary ostial atherosclerotic RAS>or=70% diameter stenosis were treated with stents selected at the discretion of the operator. Eighteen patients (32 lesions) treated with 9 different types of stents were excluded from the analysis, leaving 125 patients (69 men; mean age 67 years, range 42 to 90) with 147 lesions who received either a Radix carbofilm-coated stent in 78 (53%) lesions (68 [54%] patients) or a Palmaz Genesis bare stainless steel stent in 69 (47%) lesions (57 [46%] patients). The target vessel diameter ranged from 5 to 7 mm.

RESULTS

Baseline characteristics were similar in both groups except the mean stent diameter, which was larger in the bare stent cohort (6.4+/-0.7 versus 5.9+/-0.5 mm, p<0.001). Primary success was 100% in both groups; the initial mean diameter stenosis was reduced from 79%+/-14% and 80%+/-14% in the coated versus bare stent groups to 3+/-5% and 2+/-6%, respectively. After a mean follow-up of 22+/-5 months, the restenosis rate was 6.4% for the coated stent and 5.8% for the bare stent (p=0.87). For the entire cohort, restenosis rates varied significantly (p<0.05) according to stent diameter: 19% (5/26) for 5 mm, 4% (3/81) for 6 mm, and 2.5% (1/40) for 7 mm. In a binary logistic regression analysis including carbofilm coating, stent diameter, gender, diabetes, smoking status, and body mass index, stent diameter was the only independent predictor of restenosis (odds ratio 0.12, 95% CI 0.03 to 0.48 [p=0.003] for a 1-mm increase in vessel diameter).

CONCLUSIONS

Using modern low-profile stent devices, carbofilm coating does not significantly reduce the restenosis rate compared to a bare metal stent. With contemporary stent devices, the restenosis rate has been decreasing compared to earlier reports in the literature.

Prospective randomized comparison of early and late results of a carbonized stent versus a high-grade stainless steel stent of identical design: the PREVENT Trial [corrected]

BACKGROUND

Restenosis after coronary interventions with stent implantation is still the main obstacle of interventional cardiology. The aim of this study was to compare a carbonized and high-grade stainless steel stent of identical design with regard to early and late adverse events.

METHODS

In this prospective randomized trial the carbonized MAC stent (amg GmbH, Raesfeld-Erle, Germany) was compared with the stainless steel MAC stent of identical design. Primary end point was diameter stenosis at follow-up; secondary end points were angiographic parameters, rate of restenosis, and major cardiac adverse events (MACE; myocardial infarction, reintervention, and death).

RESULTS

Between August 1999 and June 2002, 396 patients were randomized in 2 centers of Germany. Diameter stenosis at follow-up (38.6% +/- 23.4% vs 39.1% +/- 22.2%, P = .49) as primary end point, relative late lumen loss (26.8% +/- 23.7% vs 27.7% +/- 22.3%, P = .26), absolute late lumen loss (0.92 +/- 0.71 vs 0.92 +/- 0.66 mm, P = .58), net gain (1.4 +/- 0.8 vs 1.4 +/- 0.8 mm, P = .96), as well as restenosis rates (18.0% vs 19.0%, P = .81) and MACE (13.5% vs 12.2%, P = .71) were not significantly different between the carbonized and the pure stainless steel study arm, respectively.

CONCLUSION

The hypothesis of superiority of the carbonized stent over a stainless steel stent of identical design with regard to restenosis and MACE could not be proved. Inactive coating of stents seems to have no advantage over pure stainless steel stents, which was also demonstrated in other trials. The future probably lies in active coating of stents with drugs that reduce the neointimal proliferation process.

The influence of physical stent parameters upon restenosis

In this paper we examine whether the structure, geometry and dimensions of coronary stents influence the occurrence of restenosis. Whilst many consider these parameters to be less important since the advent of drug-eluting stents, this view reveals a poor appreciation of the technological development of stents over the last 18 years. Early 'slotted tube' stents were completely inflexible and posed major problems for delivery; and early 'coil' stents had poor radial strength, allowing considerable tissue prolapse. Nowadays, we are used to greatly improved physical stent parameters, which provide better deliverability, visibility, procedural success and scaffolding performance. Many of these physical parameters also impact upon restenosis, even in the current era of drug-eluting stent. In this paper we examine the contribution of mode of expansion (self vs. balloon-expandable), design (coil vs. tube), length and width to restenosis. We also consider the more subtle influence of advanced slotted tube vs. modular design, percent metal coverage, strut thickness, strut shape, surface smoothness and alloy composition.

Comparison of early and late results of a Carbofilm-coated stent versus a pure high-grade stainless steel stent (the Carbostent-Trial)

The long-term success of coronary interventions with stents is largely determined by the development of restenosis. The aim of this study was to compare a Carbofilm-coated and a pure stainless steel stent with regard to early and late adverse events. In this prospective, randomized trial, the Carbofilm-coated Carbostent and Sirius stent (same stent design, newly developed delivery system) were compared with the stainless steel stents S660, S670, and S7 (newly developed delivery system, same principal stent design with a few changes). The primary end point was relative late luminal loss, and secondary end points were diameter stenosis at 6 months, rate of restenosis, and major adverse cardiac events (MACEs) (myocardial infarction, reintervention, and death). From March 2000 to June 2002 at 18 centers in Canada and Europe, 420 patients were randomized. Relative late luminal loss (Carbofilm 28.9 +/- 23.0% vs stainless steel 26.7 +/- 20.2%, p = 0.95) as the primary end point, absolute late luminal loss (1.00 +/- 0.72 vs 0.93 +/- 0.62 mm, p = 0.95), net gain (1.32 +/- 0.82 vs 1.40 +/- 0.74 mm, p = 0.75), and the degree of stenosis (40.7 +/- 22.9% vs 38.0 +/- 20.1%, p = 0.92), as well as restenosis rates (23.5% vs 15.9%, p = 0.09) and MACEs (20.1% vs 13.7%, p = 0.11) were not significantly different. Thus, the Carbofilm coating of stents does not lead to an improvement in angiographic results or a reduction of restenosis rate and MACEs. These results agree with other trials using inactive coatings on stents, which also could not demonstrate any advantage over pure stainless steel stents.