Prevention of restenosis after coronary angioplasty

An unusual no-reflow phenomenon due to neointimal tissue embolization during drug eluting balloon intervention in stent restenosis: A case report

Acute coronary syndrome is one of the leading causes of death worldwide. Percutaneous coronary intervention (PCI), along with various devices, have been technically developed to dramatically improve mortality risk in patients with acute myocardial infarction. However, no-reflow phenomenon still remains a problematic complication during a PCI, even in the era of drug eluting stents. There are various hypotheses and mechanisms for no-reflow phenomenon, but none have been confirmed. Treatment for no-reflow phenomenon also depends on various underlying conditions, but have not yet shown effective improvement. We presented a case of no-reflow phenomenon caused by an unusual cause.

The-374T/A Variant of the Rage Gene Promoter is Associated with Clinical Restenosis after Coronary Stent Placement

Upregulation of the receptor for advanced glycation end products (RAGE) may play a crucial role in neointimal formation upon vessel injury. The −374T/A variant of the RAGE gene promoter, which has been associated with an altered expression of the cell-surface receptor, could exert a protective effect toward the development of vascular disease. The aim of this study is to determine the impact of this common genetic variant in the occurrence of clinical in-stent restenosis after coronary stent implantation. The −374T/A polymorphism of the RAGE gene promoter was evaluated by PCR-RFLPs in 267 patients with coronary artery disease who underwent coronary stent implantation and a subsequent coronary angiography 6–9 months later for suspected restenosis. In-stent restenosis was assessed by means of quantitative angiography. Carriers of the-374AA genotype showed a significantly reduced risk of developing restenosis after percutaneous transluminal intervention than non-carriers. To determine whether the protective effect of the homozygous AA genotype toward clinical restenosis was independent of potential confounders, we performed multivariable logistic regression analysis. After allowance for clinical and biochemical risk factors and stent length, the AA genotype remained significantly associated with a reduced prevalence of in-stent restenosis. No relation was evident between the RAGE genotype and established cardiovascular risk factors. In conclusion, the −374AA genotype of the RAGE gene promoter could be associated with a reduced risk of in-stent restenosis after coronary stent implantation.

Interfacial biology of in-stent restenosis

Percutaneous angioplasty is a nonsurgical method able to restore patency in atherosclerotic blood vessels through the expansion of a balloon. The clinical outcome of this technique has been significantly enhanced by the combined deployment of a stent. Although stents are successful in the majority of cases, a large percentage of patients (20-30%) still suffer a second vessel lumen reduction known as in-stent restenosis. In-stent restenosis is recognized to be caused by the mechanical and foreign body challenges elicited by the device. Drug-eluting stents have been recently made available to tackle restenosis, but their short clinical history and high costs may limit their future use. The present review links the most recent biologic findings related to in-stent restenosis to the devices' phyisico-chemical features in an attempt to demonstrate that a new generation of stents may be developed without the need of drug elution.

Urinary trypsin inhibitor reduced inflammatory response after stent injury in minipig

This study investigated whether urinary trypsin inhibitor (UTI) inhibits neointimal formation by reducing inflammatory response after stent injury. Twenty minipigs having undergone oversized bare material stent implantation in the left anterior descending artery were randomly subdivided into two groups: a UTI group (n=10) and a control group (n=10). Two systemic markers of inflammation (serum macrophage chemoattractant protein-1 and interleukin-6 levels measured by ELISA) were increased after stent implantation, and two days after stem implantation, their levels were positively correlated with the maximal percentage of area stenosis on day 28 (r(2)=0.889 and 0.743, respectively). This effect was abolished by UTI administration. Twenty-eight days after implantation, morphometric analysis of the stented arteries revealed significantly reduced luminal stenosis (38±6% vs. 64±12%, P<0.05), a neointimal area (3.22±0.57 mm(2) vs. 5.21±1.04 mm(2), P<0.05), neointimal thickness (0.31±0.13 mm vs. 0.46±0.16 mm, P<0.05), and an inflammatory score of 1.02±0.05 vs. 1.30±0.08 in UTI-treated animals as compared with controls. Twenty-eight days after stenting, arterial nuclear factor-κB expression was 36.93±7.16% in all of the cells in controls and 23.32±4.54% in UTI-treated minipigs. UTI could reduce neointimal formation after stenting by inhibiting the local and the systemic inflammatory response. Percutaneous coronary intervention could benefit from precocious anti-inflammatory treatment.

Drug-eluting stents: a comprehensive appraisal

Cardiovascular medicine has evolved over the last few decades, with the advent of percutaneous interventional treatments. In particular, balloon angioplasty and, subsequently, coronary stenting has revolutionized our current perspective of stable and unstable coronary artery disease management. However, the long-term results of stent usage have been blighted by the dual problems of in-stent restenosis and stent thrombosis. Whilst stent thrombosis became much less frequent with the introduction of dual-antiplatelet therapy, restenosis remained a significant problem. Intense work on stent development has successfully led to the introduction of drug-eluting stents (DES) in an effort to address this problem. Randomized trials have consistently proven the superior efficacy of DES over bare metal stents, in elective patients, acute coronary syndromes and patients with diabetes mellitus. Nevertheless, the routine use of DES in by-pass venous graft disease remains debatable. The initial DES used sirolimus and paclitaxel are now being joined by newer stents releasing drugs, such as everolimus, zotarolimus and tacrolimus. Ongoing developments with the stent platform and the polymer coating are also gradually improving the performance of these stents in clinical practice. More recently, the idea of antibody-coated stents that would encourage epithelialization of stent struts by endothelial progenitor cells recruitment has gained attraction among interventionists, with a possible beneficial impact on reducing the incidence of restenosis.

Enhancement in anti-proliferative effects of paclitaxel in aortic smooth muscle cells upon co-administration with ceramide using biodegradable polymeric nanoparticles

PURPOSE

Using a combination of paclitaxel (PTX), and the apoptotic signaling molecule, C6-ceramide (CER), the enhancement in anti-proliferative effect of human aortic smooth muscle cells (SMC) was examined by administering in polymeric nanoparticles.

METHODS

PTX- and CER-loaded poly(ethylene oxide)-modified poly(epsilon caprolactone) (PEO-PCL) nanoparticles were formulated by solvent displacement and characterized. The uptake and intracellular localization of the nanoparticle in SMC was examined using Z-stack fluorescent confocal microscopy. Anti-proliferative and pro-apoptotic effects of SMC were determined upon administration of PTX and CER, either as single agent or in combination, in aqueous solution and in PEO-PCL nanoparticle formulations.

RESULTS

High encapsulation efficiencies (i.e., >95%) of PTX and CER at 10% (w/w) loading were attained in the PEO-PCL nanoparticles of around 270 nm in diameter. Fluorescence confocal analysis showed that nanoparticle delivery did facilitate cellular uptake and internalization. Additionally, combination of PTX and CER delivery in PEO-PCL nanoparticles was significantly more effective in decreasing the proliferation of SMC, probably by enhancing the apoptotic response.

CONCLUSIONS

The results of this study show that combination of PTX and CER when administered in PEO-PCL nanoparticles can significantly augment the anti-proliferative effect in SMC. This strategy may potentially be useful in the treatment of coronary restenosis.

Drug-eluting stent: a review and update

The development of stent has been a major advance in the treatment of obstructive coronary artery disease since the introduction of balloon angioplasty. However, neointimal hyperplasia occurring within the stent leading to in-stent restenosis is a main obstacle in the long-term success of percutaneous coronary intervention (PCI). The recent introduction of drug-eluting stents (DES) contributes a major breakthrough to interventional cardiology. Many large randomized clinical trials using DES have shown a remarkable reduction in angiographic restenosis and target vessel revascularization when compared with bare metal stents. The results of these trials also appear to be supported by evidence from everyday practice and noncontrolled clinical trials. However, the expanded applications of DES, especially in treating complex lesions such as left main trunk, bifurcation, saphenous vein graft lesions, or in-stent restenosis, are still under evaluation with ongoing studies. With the availability of different types of DES in the market, the issue of cost should not be a deterrent and DES will eventually be an economically viable option for all patients. The adoption of DES in all percutaneous coronary intervention may become a reality in the near future. In this review article, we summarize the recent development and progress of DES as well as compare and update the results of clinical trials.

Is inflammation a contributor for coronary stent restenosis?

The development of coronary stent has revolutionized the field of interventional cardiology by reducing the incidence of restenosis after balloon angioplasty. Despite significant progress in its prevention and treatment, however, in-stent restenosis (ISR) is still common, and remains a challenge for the interventional cardiologist. Restenosis after stent implantation is mainly caused by neointimal proliferation through the stent struts. Currently, there are three major factors has been demonstrated to be contributors for ISR, namely patients-, lesion- and genetic-related factors in large number of clinical trials. However, the triggers and pathophysiological mechanisms for ISR are not fully elucidated. Experimental as well as clinical studies indicate a marked activation of inflammatory cells at the site of stent structs, which are likely to play a key role in the process of neointimal proliferation and stent restenosis. Those data suggest that inflammation may be a major contributor for ISR. In fact, coronary stenting is a strong inflammatory stimulus and the acute systemic response to local inflammation produced by coronary stenting is highly individual and predicts restenosis and event-free survival. Thus, the attention should be paid on anti-inflammatory therapeutic approaches for ISR, and the benefit of anti-inflammatory therapy during the periprocedural period and long-term follow-up is dependent on the inflammatory status. Measurement of cytokine and acute phase proteins, such as C-reactive protein, therefore, may be important to identify high-risk subjects and develop specific treatment tailored to the individual patients.

Expandable tracheal stenting for benign disease: worth the complications?

OBJECTIVES

To characterize the limitations of self-expandable stents in the management of benign tracheal stenosis, we performed a retrospective review at a tertiary care medical center.

METHODS

Patients who underwent tracheal stenting were assessed for the cause and severity of tracheal stenosis, comorbidities, stent-related complications, and follow-up airway procedures.

RESULTS

Sixteen adults (12 women, 4 men; mean age, 47 years) had a total of 26 stents placed for benign disease. Intubation-related stenoses were most frequent (81%). The average follow-up time was 20 months (range, 1 to 40 months). Each stent remained functional for an average of 12.4 months. In the study group, 87% had a complication that required surgical intervention to maintain a patent airway. The most common problem was granulation tissue formation at the ends of the stent causing airway restenosis (81%), and 5 patients (31%) required tracheotomy as a result of restenosis around the stent. Fourteen of the stents (56%) were removed or expelled from the patients.

CONCLUSIONS

The implantation of self-expandable stents is a minimally invasive method of managing benign tracheal stenosis. Although a small subset of patients may benefit from placement, the majority of patients have complications that require intervention to maintain a patent airway. Thoughtful discretion is critical in selecting patients for this intervention.

Transluminal Stenting for Femoropopliteal Occlusive Disease: Analysis of Restenosis by Serial Arteriography

Our objective was to evaluate restenosis after stenting of femoropopliteal occlusions and the impact of percutaneous transluminal angioplasty (PTA) on recurrent stenosis. We used a retrospective analysis of contrast angiograms obtained during follow-up of stented limbs. Subjects included 27 claudicants (34 limbs) who had complete superficial femoral artery occlusion treated with PTA and Wallstents at the Veterans Adminstration Medical Center. During follow-up, 31 PTAs, three thrombolytic treatments, and one additional stenting were performed. Outcome was measured by contrast angiography. Primary patency at 1 and 3 years was 38% and 8% after stenting, and secondary patency (PTA required at least once in 21/34 limbs) was 89% and 55%, respectively. PTA performed during follow-up reduced within-stent restenosis on average from 48.3 +/- 13.6% to 22.8 +/- 18.0%. Recurrent stenosis after PTA measured 14.9 +/- 10.9 months later was 46.8 +/- 16.7%, showing little permanent impact of PTA on stenosis. Severe within-stent stenosis develops commonly after initial stenting of complete femoropopliteal occlusions. Supplemental PTA performed during follow-up provides immediate improvement in lumen diameter, but severe restenosis is still likely to recur.

Drug-Eluting Coronary Stents

The introduction and widespread use of coronary stents have been the most important advancement in the percutaneous treatment of coronary artery disease since the introduction of balloon angioplasty. Coronary artery stents reduce the rate of angiographic and clinical restenosis compared to balloon angioplasty. This angiographic restenosis was further reduced with the introduction of drug-eluting stents and hence further reduction in the frequency of major adverse cardiac events. Herein we present a comprehensive and up-to-date review about the use of drug-eluting stents in the treatment of coronary artery disease.

Correction of cellular phenotypes of Hutchinson-Gilford Progeria cells by RNA interference

The great majority of cases of the Hutchinson-Gilford progeroid syndrome (HGPS) ("Progeria of Childhood'') are caused by a single nucleotide mutation (1824 C->T) in the LMNA gene which encodes lamin A and C, nuclear intermediate filaments that are important components of the nuclear lamina. The resultant mutant protein (Delta50 lamin A) is thought to act in a dominant fashion. We exploited RNA interference technology to suppress Delta50 lamin A expression, with the long range goal of intervening in the pathogenesis of the coronary artery atherosclerosis that typically leads to the death of HGPS patients. Short hairpin RNA (shRNA) constructs were designed to target the mutated pre-spliced or mature LMNA mRNAs, and were expressed in HGPS fibroblasts carrying the 1824 C->T mutations using lentiviruses. One of the shRNAs targeted to the mutated mRNA reduced the expression levels of Delta50 lamin A to 26% or lower. The reduced expression was associated with amelioration of abnormal nuclear morphology, improvement of proliferative potential, and reduction in the numbers of senescent cells. These findings provide a rationale for potential gene therapy.

How should patients with unstable angina and non-ST-segment elevation myocardial infarction be managed? A meta-analysis of randomized trials

PURPOSE

Patients with unstable angina or non-ST-segment elevation myocardial infarction (MI) may be managed with either an "invasive" or "conservative" strategy. It is unclear which of these strategies is superior.

METHODS

We identified studies with MEDLINE and EMBASE searches (1966-September 2003) and by reviewing reference lists. Studies were included if they were randomized controlled trials comparing management strategies for patients in the early post-unstable angina/non-ST-segment elevation MI period and had follow-up data for at least 3 months.

RESULTS

Seven trials that randomized a total of 9212 patients were included. The pooled odds ratio (OR) for all-cause mortality was 0.96 (95% confidence interval [CI]: 0.72 to 1.27). The occurrence of fatal or nonfatal re-infarction was reduced with an invasive strategy (OR 0.73; 95% CI: 0.61 to 0.88) as was readmission to hospital (OR 0.67; 95% CI: 0.48 to 0.94). The endpoints of nonfatal MI and the composite of death or nonfatal MI showed nonsignificant trends favoring an invasive strategy. Trials that included a higher proportion of patients with ST-segment depression on admission and trials in which a larger proportion of patients underwent revascularization showed a greater magnitude of benefit for an invasive strategy.

CONCLUSION

For patients with unstable angina/non-ST-segment elevation MI, an invasive strategy reduces rates of fatal or nonfatal re-infarction and hospital readmission, but not all-cause mortality, when compared with a noninvasive strategy. These results suggest that an invasive management strategy should be considered for all patients with unstable angina/non-ST-segment elevation MI and perhaps in particular those with ST-segment depression.