Drug-Eluting Stent Update 2007

Current trends in coronary revascularization

The options for coronary revascularization broadened in recent years with the introduction of bare-metal stents in the 1990s and drug-eluting stents in 2003. Since then, the rates of percutaneous coronary intervention (PCI) have increased whereas the use of coronary artery bypass grafting (CABG) has decreased. Although historically there have been disparities in the use of revascularization procedures in women, the elderly, and nonwhite patients, there is some evidence to suggest these gaps have narrowed in recent years. In any given clinical circumstance, there is ongoing debate as to whether PCI or CABG is the more appropriate revascularization method depending on coronary anatomy, ventricular function, and associated conditions. Also, trends in coronary revascularization are potentially influenced by emerging clinical evidence and new technologies, national guidelines and appropriateness criteria, procedure reimbursement, and changes in the population being treated. Accordingly, it is unclear whether the trend in increased use of PCI versus CABG will continue.

Low-molecular-weight heparin versus unfractionated heparin in acute ST-segment elevation myocardial infarction patients undergoing primary percutaneous coronary intervention with drug-eluting stents

BACKGROUND

Whether low-molecular-weight heparin (LMWH) is superior to unfractionated heparin (UFH) in acute ST-segment elevation myocardial infarction (STEMI) patients undergoing primary percutaneous coronary intervention (PCI) with drug-eluting stents (DESs) remains unclear.

METHODS

A total of 3,372 STEMI patients who underwent primary PCI with DESs received either LMWH (n = 1,531 patients, subcutaneous enoxaparin 1 mg/kg, bid for 3-5 days plus reduced dose of UFH [50 U/kg] during PCI) or UFH alone (n = 1,841 patients, intravenous bolus injection of 5,000 U, followed by 24,000 U/d infusion for at least 48 hours). The bleeding events and clinical outcomes during in-hospital and at 8 months were compared.

RESULTS

The incidences of major and minor bleeding events were similar between the 2 groups. Multivariable Cox regression analysis showed that LMWH group had lower incidences of cardiac death (adjusted odds ratio [OR] 0.55, 95% CI 0.39-0.77, P < .001), total death (adjusted OR 0.50, 95% CI 0.37-0.68, P < .001), and total major adverse cardiac events (adjusted OR 0.77, 95% CI 0.62-0.95, P = .017) at 8 months as compared with UFH group. Similar results were obtained across different subgroups including different DESs, age, and sex.

CONCLUSIONS

The LMWH enoxaparin combined with reduced dose of UFH (50 U/kg) administration as an adjunctive antithrombotic therapy in STEMI patients undergoing primary PCI with DESs seems to be safe and efficacious. However, randomized clinical trials are needed to confirm this conclusion.

Drug-eluting stents for the treatment of acute myocardial infarction: the view to the HORIZONS

Drug-eluting stents (DES) offer an attractive option for the treatment of acute thrombotic lesions during acute ST-elevation myocardial infarction (STEMI) due to their ability to inhibit restenosis. Several randomised trials have demonstrated the efficacy of DES in reducing target vessel revascularisation (TVR) in this setting. However, several registries of real-world patients receiving DES for STEMI have raised long-term safety concerns about DES use in this patient subset. Given the inherent limitations of registry data, this issue is likely to remain unresolved until further data is made available from large-scale ongoing trials with long-term follow-up such as the HORIZONS-AMI trial.

Integrative genomics identifies DSCR1 (RCAN1) as a novel NFAT-dependent mediator of phenotypic modulation in vascular smooth muscle cells

Vascular smooth muscle cells (SMCs) display remarkable phenotypic plasticity in response to environmental cues. The nuclear factor of activated T-cells (NFAT) family of transcription factors plays a critical role in vascular pathology. However, known functional NFAT gene targets in vascular SMCs are currently limited. Publicly available whole-genome expression array data sets were analyzed to identify differentially expressed genes in human, mouse and rat SMCs. Comparison between vehicle and phenotypic modulatory stimuli identified 63 species-conserved, upregulated genes. Integration of the 63 upregulated genes with an in silico NFAT-ome (a species-conserved list of gene promoters containing at least one NFAT binding site) identified 18 putative NFAT-dependent genes. Further intersection of these 18 potential NFAT target genes with a mouse in vivo vascular injury microarray identified four putative NFAT-dependent, injury-responsive genes. In vitro validations substantiated the NFAT-dependent role of Cyclooxygenase 2 (COX2/PTGS2) in SMC phenotypic modulation and uncovered Down Syndrome Candidate Region 1 (DSCR1/RCAN1) as a novel NFAT target gene in SMCs. We show that induction of DSCR1 inhibits calcineurin/NFAT signaling through a negative feedback mechanism; DSCR1 overexpression attenuates NFAT transcriptional activity and COX2 protein expression, whereas knockdown of endogenous DSCR1 enhances NFAT transcriptional activity. Our integrative genomics approach illustrates how the combination of publicly available gene expression arrays, computational databases and empirical research methods can answer specific questions in any cell type for a transcriptional network of interest. Herein, we report DSCR1 as a novel NFAT-dependent, injury-inducible, early gene that may serve to negatively regulate SMC phenotypic switching.

p27kip1-838C>A single nucleotide polymorphism is associated with restenosis risk after coronary stenting and modulates p27kip1 promoter activity

BACKGROUND

The cyclin-dependent kinase inhibitor p27(kip1) is a key regulator of smooth muscle cell and leukocyte proliferation in vascular disease, including in-stent restenosis. We therefore hypothesized that common genetic variations or single nucleotide polymorphisms in p27(kip1) may serve as a useful tool in risk stratification for in-stent restenosis.

METHODS AND RESULTS

Three single nucleotide polymorphisms concerning the p27(kip1) gene (-838C>A, rs36228499; -79C>T, rs34330; +326G>T, rs2066827) were determined in a cohort of 715 patients undergoing coronary angioplasty and stent placement. We discovered that the p27(kip1)-838C>A single nucleotide polymorphism is associated with clinical in-stent restenosis; the -838AA genotype decreases the risk of target vessel revascularization (hazard ratio, 0.28; 95% confidence interval, 0.10 to 0.77). This finding was replicated in another cohort study of 2309 patients (hazard ratio, 0.61; 95% confidence interval, 0.40 to 0.93). No association was detected between this end point and the p27(kip1)-79C>T and +326G>T single nucleotide polymorphisms. We subsequently studied the functional importance of the -838C>A single nucleotide polymorphism and detected a 20-fold increased basal p27(kip1) transcriptional activity of the -838A allele containing promoter.

CONCLUSIONS

Patients with the p27(kip1)-838AA genotype have a decreased risk of in-stent restenosis corresponding with enhanced promoter activity of the -838A allele of this cell-cycle inhibitor, which may explain decreased smooth muscle cell proliferation.

Coating irregularities of durable polymer-based drug-eluting stents as assessed by scanning electron microscopy

AIMS

To classify and quantify post-expansion irregularities in durable polymer-based coatings of drug-eluting stents (DES).

METHODS AND RESULTS

Taxus Liberté, Endeavor Sprint, Endeavor Resolute and Xience V DES (three samples of each) were explored by light microscopy and scanning electron microscopy (SEM) following expansion at 14 atm in water. Incidence and size of irregularities were measured during thorough quantitative examinations of a 360 SEM images. DES types examined showed a significant difference in the incidence of irregularities (p<0.0001; 6.6+/-4.2/image at 60-fold magnification) with typical patterns specific for each DES. All types showed areas with bare metal-aspects, but incidence, shape, and size differed largely: Sprint showed the largest areas. Cracks were only found in Sprint and Resolute, while wrinkles were seen exclusively in Taxus Liberté and Xience V (p<0.0001). The coating of each DES type showed some inhomogeneity of distribution, but the incidence differed (p<0.0001) and was least in Taxus Liberté, which, on the other hand, was the only DES that showed webbing with large bare-metal exposure.

CONCLUSIONS

The incidence and size of various coating irregularities on different types of DES varied widely. These data may be considered in ongoing discussions on the differences between DES and may serve as reference to compare novel DES.

Triple Versus Dual Antiplatelet Therapy in Patients With Acute ST-Segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention

Background— Whether triple antiplatelet therapy is superior or similar to dual antiplatelet therapy in patients with acute ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention in the era of drug-eluting stents remains unclear.

Methods and Results— A total of 4203 ST-segment elevation myocardial infarction patients who underwent primary percutaneous coronary intervention with drug-eluting stents were analyzed retrospectively in the Korean Acute Myocardial Infarction Registry (KAMIR). They received either dual (aspirin plus clopidogrel; dual group; n=2569) or triple (aspirin plus clopidogrel plus cilostazol; triple group; n=1634) antiplatelet therapy. The triple group received additional cilostazol at least for 1 month. Various major adverse cardiac events at 8 months were compared between these 2 groups. Compared with the dual group, the triple group had a similar incidence of major bleeding events but a significantly lower incidence of in-hospital mortality. Clinical outcomes at 8 months showed that the triple group had significantly lower incidences of cardiac death (adjusted odds ratio, 0.52; 95% confidence interval, 0.32 to 0.84; P =0.007), total death (adjusted odds ratio, 0.60; 95% confidence interval, 0.41 to 0.89; P =0.010), and total major adverse cardiac events (adjusted odds ratio, 0.74; 95% confidence interval, 0.58 to 0.95; P =0.019) than the dual group. Subgroup analysis showed that older (>65 years old), female, and diabetic patients got more benefits from triple antiplatelet therapy than their counterparts who received dual antiplatelet therapy.

Conclusions— Triple antiplatelet therapy seems to be superior to dual antiplatelet therapy in patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention with drug-eluting stents. These results may provide the rationale for the use of triple antiplatelet therapy in these patients.

The neointimal response to stents eluting tacrolimus from a degradable coating depends on the balance between polymer degradation and drug release

AIMS

To study how the balance between tacrolimus elution and polymer degradation from drug-eluting stents (DES) affects neointimal thickening (NIT) in swine coronary arteries.

METHODS AND RESULTS

We assessed a fast-degrading high dose (2 microg/mm2), a slow degrading low dose (1 microg/mm2) or polymer-only coated DES (Pol) versus bare metal stent (BMS). Coronary segments were pre-injured with a balloon/artery ratio of 1.1 to 1.3. Then stents were implanted at that site with a stent/artery ratio of 1.1, with a follow-up period of 5 to 180 days. Histology showed a well endothelialised neointima (82 +/- 1% in high dose DES vs. 93 +/- 8% in BMS) already at five days, without differences in eNOS expression. Morphometry indicated that neointimal thickness in DES was significantly reduced as compared to BMS and Pol at 28 and 90 days. Polymer degradation products induced a distinct inflammatory response which was effectively suppressed in DES. Between 90 and 180 days, however, the slow degrading low-dose stent showed catch-up of NIT.

CONCLUSIONS

Tacrolimus eluted from a biodegradable stent coating can suppress the inflammatory effect of the coating degradation products if the balance between the drug levels and the degradation products is favorable.

Drug-eluting or bare-metal stents for large coronary vessel stenting? The BASKET-PROVE (PROspective Validation Examination) trial: study protocol and design

BACKGROUND

Based on a subgroup analysis of 18-month BAsel Stent Kosten Effektivitäts Trial (BASKET) outcome data, we hypothesized that very late (> 12 months) stent thrombosis occurs predominantly after drug-eluting stent implantation in large native coronary vessel stenting.

METHODS

To prove or refute this hypothesis, we set up an 11-center 4-country prospective trial of 2260 consecutive patients treated with > or = 3.0-mm stents only, randomized to receive Cypher (Johnson & Johnson, Miami Lakes, FL), Vision (Abbott Vascular, Abbott Laboratories, IL), or Xience stents (Abbott Vascular). Only patients with left main or bypass graft disease, in-stent restenosis or stent thrombosis, in need of nonheart surgery, at increased bleeding risk, without compliance/consent are excluded. All patients are treated with dual antiplatelet therapy for 12 months. The primary end point will be cardiac death/nonfatal myocardial infarction after 24 months with further follow-up up to 5 years.

RESULTS

By June 12, 229 patients (10% of the planned total) were included with a baseline risk similar to that of the same subgroup of BASKET (n = 588).

CONCLUSIONS

This study will answer several important questions of contemporary stent use in patients with large native vessel stenting. The 2-year death/myocardial infarction-as well as target vessel revascularization-and bleeding rates in these patients with a first- versus second-generation drug-eluting stent should demonstrate the benefit or harm of these stents compared to cobalt-chromium bare-metal stents in this relevant, low-risk group of everyday patients. In addition, a comparison with similar BASKET patients will allow to estimate the impact of 12- versus 6-month dual antiplatelet therapy on these outcomes.