Localized Hypersensitivity and Late Coronary Thrombosis Secondary to a Sirolimus-Eluting Stent

Prevention of restenosis by a novel drug-eluting stent system with a dose-adjustable, polymer-free, on-site stent coating

AIMS

Drug-eluting stents (DES) represent a major advance in interventional cardiology. Along with the success shown, current DES also present limitations related to the presence of polymer-coating, fixed drug, and dose used. With the ISAR (Individualized Drug-Eluting Stent System to Abrogate Restenosis) project, a DES system has been developed that permits individualized choice of the drug and dose to use for the given patient. The objective of this prospective dose finding study was to assess the feasibility, safety, and efficacy of a polymer-free on-site stent coating with increasing rapamycin doses.

METHODS AND RESULTS

In this dose finding study, 602 patients were sequentially enrolled in four groups: microporous bare metal stent (BMS), DES stents coated with a 0.5, 1.0, and 2.0% rapamycin solution. The angiographic in-segment restenosis rate at follow-up angiography was the primary study endpoint. In-segment restenosis was significantly reduced from 25.9% with BMS to 18.9, 17.2, and 14.7% with 0.5, 1.0, and 2.0% rapamycin-eluting stents, respectively (P=0.024). Similarly, the need for target lesion revascularization at 1 year follow-up was reduced from 21.5% with BMS to 16.4, 12.6, and 8.8% with 0.5, 1.0, and 2.0% rapamycin-eluting stents, respectively (P=0.006).

CONCLUSION

The placement of polymer-free stents coated on-site with rapamycin is feasible and safe. Furthermore, a dose-dependent efficacy in restenosis prevention is achievable with this new DES concept.

Eosinophilic infiltration in restenotic tissue following coronary stent implantation

OBJECTIVES

The aim of our study was to compare the histopathological features of restenotic tissue after balloon angioplasty and after stent placement. We emphasized on specific types of inflammatory cells to evaluate the type of tissue immune response in both situations.

METHODS

A total of 32 patients underwent elective directional coronary atherectomy; 16 patients had restenosis after balloon angioplasty, 16 patients had in-stent restenosis (ISR). Atherectomy specimens were stained with antibodies against T cells, eosinophils, smooth muscle cell actin, macrophages and with antibodies against T cell activation markers. Quantitative morphometric analysis was performed using image analysis software.

RESULTS

In-stent restenotic tissue contained more smooth muscle cells (P < 0.001), anti-CD3 positive T cells (P < 0.001) and eosinophils (P = 0.012). Anti-CD40L positive activated T cells were more numerous in ISR lesions (P = 0.003) and were frequently clustered around stent imprints in the tissue. Five ISR specimens contained grossly visible stent fragments amidst the restenotic tissue. In all cases of balloon restenosis, T cells and eosinophils (if present) were concentrated around lipid rich tissue.

CONCLUSIONS

Our study indicates involvement of inflammatory responses in both types of restenosis, with significantly more eosinophils encountered in case of in-stent restenosis. In contrast with clustering of inflammatory cells around stent struts after stent placement, the inflammatory cells in balloon restenosis were located in association with lipid rich tissue, suggesting different inflammatory triggers in balloon restenosis and in-stent restenosis.

Coronary aneurysm after implantation of a paclitaxel-eluting stent

Formation of coronary aneurysm is a rare complication of stenting with bare metal stents, but based on experimental studies drug-eluting stents may induce toxic effects on the vessel wall with incomplete stent apposition, aneurysm formation and with the potential of stent thrombosis or vessel rupture. We present a 43-year-old man who developed a coronary aneurysm in the right coronary artery 6 months after receiving a paclitaxel-eluting stent. The patient was asymptomatic and the aneurysm was detected in a routine control. Angiography and intracoronary ultrasound demonstrated lack of contact between stent and vessel wall in a 15-mm long segment with maximal aneurysm diameter of 6.0 mm. The patient was successfully treated with a graft stent.

Randomized comparison of a titanium-nitride-oxide-coated stent with a stainless steel stent for coronary revascularization: the TiNOX trial

BACKGROUND

Stent coating with titanium-nitride-oxide has been shown to reduce neointimal hyperplasia in the porcine restenosis model. We designed a prospective, randomized, clinical study to investigate the safety and efficacy of titanium-nitride-oxide-coated stents compared with stainless steel stents.

METHODS AND RESULTS

Ninety-two patients with de novo lesions were randomly assigned to treatment with titanium-nitride-oxide-coated stents (n=45) or stainless steel stents of otherwise identical design (n=47; control). Baseline characteristics were similar in both groups. At 30 days, no stent thromboses or other adverse events had occurred in either group. Quantitative coronary angiography at 6 months revealed lower late loss (0.55+/-0.63 versus 0.90+/-0.76 mm, P=0.03) and percent diameter stenosis (26+/-17% versus 36+/-24%, P=0.04) in lesions treated with titanium-nitride oxide-coated than in control stents. Binary restenosis was reduced from 33% in the control group to 15% in the titanium-nitride oxide-coated stent group (P=0.07). Intravascular ultrasound studies at 6 months showed smaller neointimal volume in titanium-nitride-oxide-coated stents than in control stents (18+/-21 versus 48+/-28 mm3, P<0.0001). Major adverse cardiac events at 6 months were less frequent in titanium-nitride-oxide-coated stents than in control stent-treated patients (7% versus 27%, P=0.02), largely driven by a reduced need for target-lesion revascularization (7% versus 23%, P=0.07).

CONCLUSIONS

Revascularization with titanium-nitride-oxide-coated stents is safe and effective in patients with de novo native coronary artery lesions. Titanium-nitride-oxide-coated stents reduce restenosis and major adverse cardiac events compared with stainless steel stents of otherwise identical design.

Intravascular stents in the last and the next 10 years

The first balloon-expandable coronary stent was approved "for the prevention of restenosis" in 1994, the same year that the Journal of Endovascular Therapy was inaugurated. Since then, the development of the stent has paralleled the evolution of endovascular intervention as a new specialty. Innovators have pushed to explore new and varied stent applications outside the coronary arteries. Carotid stenting, transjugular intrahepatic portocaval shunts, and covered stents are a few of these new applications that have now become commonplace. Dozens of stent designs and several new materials have been tested to solve the problem of in-stent restenosis, but it is the drug-eluting stent (DES) that has emerged as the most promising, at least in the coronary arteries. However, the benefits of DES technology are not likely to be effective in the more pervasive forms of in-stent restenosis, such as encountered in the femoropopliteal segment. In the future, technologies aimed at stimulating rather than inhibiting tissue response to an implant may be part of the next wave of developments, as we take aim against the poor and/or slow tissue incorporation that manifests as leaks and dislodgement. In the superficial femoral artery, for example, mechanical stresses that cause fractures and dislocations may be addressed by using a very flexible endovascular device with a tissue-friendly inner surface that promotes rapid stent endothelialization to counter the biological effects of motion and microtrauma. The rapidly developing fields of nanotechnology, microelectronics, and advanced materials technology will enable the surface engineer to design molecular-specific surfaces for a new generation of vascular devices. Interactive implantable or injectable microdevices aimed at providing specific information upon demand from an external source will revolutionize disease prevention, as emphasis shifts toward monitoring cardiovascular risk exposure. There is no doubt that during the next 10 years, we will witness impressive technological progress in the field of cardiovascular implantable devices.

Inhibition of Neointima Formation by a Novel Drug-Eluting Stent System That Allows for Dose-Adjustable, Multiple, and On-Site Stent Coating

OBJECTIVE

The risk of in-stent restenosis can be considerably reduced by stents eluting cytostatic compounds. We created a novel drug-eluting stent system that includes several new features in the rapidly evolving field of stent-based drug delivery.

METHODS AND RESULTS

The aim of the present study was the preclinical evaluation of a stent-coating system permitting individual, on-site coating of stents with a unique microporous surface allowing for individualizable, dose-adjustable, and multiple coatings with identical or various compounds, designated ISAR (individualizable drug-eluting stent system to abrogate restenosis). Stents were coated with 0.75% rapamycin solution, and high-performance liquid chromatography (HPLC)-based determination of drug release profile indicated drug release for >21 days. Rapamycin-eluting microporous (REMP) stents implanted in porcine coronary arteries were safe. To determine the efficacy of REMP stents, this novel drug-eluting stent platform was compared with the standard sirolimus-eluting stent. At 30 days, in-stent neointima formation in porcine coronary arteries was similar in both groups, yielding a significant decrease of neointimal area and injury-dependent neointimal thickness compared with bare-metal stents.

CONCLUSIONS

The ISAR drug-eluting stent platform as a novel concept for stent coating allows for a safe, effective, on-site stent coating process, thus justifying further clinical evaluation to decrease in-stent restenosis in humans.

Role of oral rapamycin to prevent restenosis in patients with de novo lesions undergoing coronary stenting: results of the Argentina single centre study (ORAR trial)

OBJECTIVE

To assess the role of oral rapamycin in the prevention of coronary restenosis in patients undergoing coronary stenting.

METHODS

From December 2001 through February 2003, 76 patients with 103 de novo lesions treated percutaneously with bare stents received a loading dose of oral rapamycin 6 mg followed by a daily dose of 2 mg during 28 days in phase I (49 arteries in 34 patients) and 2 mg/day plus 180 mg/day of diltiazem in phase II (54 arteries in 42 patients). Rapamycin blood concentrations were measured in all patients. A six month follow up angiogram was performed in 82.5% (85 of 103 arteries). Follow up angiographic binary restenosis (> 50%), target vessel revascularisation, late loss, treatment compliance, and major adverse cardiovascular events were analysed and correlated with rapamycin concentrations.

RESULTS

Rapamycin was well tolerated and only three patients discontinued the treatment for mild side effects. Angiographic restenosis was found in 15% of the arteries with angiographic restudy (13 of 85). The target vessel had been revascularised at follow up in 13.6% of the 103 vessels initially treated (14 of 103) and in 18.4% of the 76 patients (14 of 76). In-stent restenosis in phase I was 19% compared with 6.2% in phase II (p = 0.06). Angiographic in-stent restenosis in lesions of patients with rapamycin blood concentrations > or = 8 ng/ml was 6.2% and with rapamycin concentrations < 8 ng/ml was 22% (p = 0.041). Late loss was also significantly lower when rapamycin concentrations were > or = 8 ng/ml (0.6 mm v 1.1 mm, p = 0.031). A Pearson test showed a linear correlation between follow up late loss and rapamycin blood concentration (r = -0.826, p = 0.008).

CONCLUSION

Oral rapamycin administered for one month after percutaneous coronary intervention was safe and with few minor side effects. High rapamycin blood concentrations were associated with significantly lower late loss and angiographic in-stent restenosis.

Meta-analysis comparing drug-eluting stents with bare metal stents

We performed a meta-analysis of 10 randomized trials of 5,066 patients with 6 to 12 months of follow-up. The summary risk differences excluded any major differences between the 2 types of stents for death (0.12%, 95% confidence interval [CI] -0.34% to 0.58%, p = 0.60) and overall myocardial infarction (0.04%, 95% CI -0.72% to 0.81%, p = 0.91). There was a modest increase in the risk of Q-wave myocardial infarction with drug-eluting stents (0.36%, 95% CI -0.04% to 0.77%, p = 0.080) but no difference in non-Q-wave myocardial infarction (-0.26%, 95% CI -0.95% to 0.43%, p = 0.47). The trend for increased risk of Q-wave myocardial infarction was seen for paclitaxel and sirolimus stents (risk differences 0.28% and 0.58%, respectively). Drug-eluting stents also had a nonsignificant trend for higher risk of thrombosis (0.29%, 95% CI -0.08% to 0.66%, p = 0.13). We conclude that sirolimus- and paclitaxel-eluting stents are equivalent to bare-metal stents in terms of mortality and overall myocardial infarction risk for the first year of follow-up; the meta-analysis excludes with considerable confidence the presence of large, clinically relevant differences for these outcomes.

Thirty-day incidence and six-month clinical outcome of thrombotic stent occlusion after bare-metal, sirolimus, or paclitaxel stent implantation

OBJECTIVES

We sought to determine the real-world incidence of angiographically confirmed and possible stent thrombosis (ST) in an unrestricted population during the first 30 days after bare-metal stent (BMS), sirolimus-eluting stent (SES), and paclitaxel-eluting stent (PES) implantation.

BACKGROUND

Current data on ST in drug-eluting stents (DES) have come from randomized trials with strict entry criteria, which limits their generalizability to daily practice.

METHODS

The study population comprised three sequential cohorts of 506 consecutive patients with BMS, 1,017 consecutive patients with SES, and 989 consecutive patients treated with PES.

RESULTS

In the first 30 days after stent implantation, 6 BMS (1.2%, 95% confidence interval [CI] 0.5% to 2.6%; p = 0.9), 10 SES (1.0%, 95% CI 0.5% to 1.8%), and 10 PES (1.0%, 95% CI 0.6% to 1.9%) patients developed angiographically proven ST. Multiple potential risk factors were identified in most patients with ST. Bifurcation stenting in the setting of acute myocardial infarction was an independent risk factor for angiographic ST in the entire population (odds ratio [OR] 12.9, 95% CI 4.7 to 35.8, p < 0.001). In patients with DES who had angiographic ST, 30-day mortality was 15%, whereas another 60% suffered a nonfatal myocardial infarction; no further deaths occurred during six months of follow-up. Including possible cases, 7 BMS (1.4%, 95% CI 0.7% to 2.8%), 15 SES (1.5%, 95% CI 0.9% to 2.4%), and 16 PES (1.6%, 95% CI 1.0% to 2.6%) patients had ST.

CONCLUSIONS

The unrestricted use of SES or PES is associated with ST rates in the range expected for BMS. Stent thrombosis was associated with a high morbidity and mortality. Bifurcation stenting, when performed in patients with acute myocardial infarction, was associated with an increased risk of ST.

Potent inhibitory effect of sirolimus on circulating vascular progenitor cells

BACKGROUND

Neointimal hyperplasia is the major cause of in-stent restenosis (ISR). The sirolimus-eluting stent (SES) has emerged as a promising therapy to prevent ISR; however, the exact mechanism by which locally delivered sirolimus, an immunosuppressive agent, prevents ISR remains unknown. Recent evidence suggests that circulating progenitor cells may contribute to neointimal formation.

METHODS AND RESULTS

Mononuclear cells (MNCs) were isolated from peripheral blood of healthy human volunteers. Smooth muscle (SM)-like cells outgrew from the culture of MNCs (1x10(6)) in the presence of platelet-derived growth factor-BB and basic fibroblast growth factor, whereas endothelial cell-like cells were obtained in the presence of vascular endothelial growth factor. Sirolimus potently inhibited SM-like cell outgrowth. The number of SM-like cells was significantly reduced at a concentration as low as 0.1 ng/mL (15.9+/-5.8% of control, P<0.001). Sirolimus also exerted an inhibitory effect on endothelial cell-like cells that originated from MNCs. Wire-mediated vascular injury was induced in femoral arteries of bone marrow chimeric mice. Either vehicle or sirolimus was administered locally to the perivascular area of the injured arteries. Sirolimus significantly reduced neointima hyperplasia at 4 weeks (intima/media ratio 2.0+/-0.3 versus 1.0+/-0.2, P<0.05) with a decreased number of bone marrow-derived SM-like cells and hematopoietic cells in the lesion. Reendothelialization was retarded in the arteries treated with sirolimus.

CONCLUSIONS

The potent inhibitory effects of sirolimus on circulating smooth muscle progenitor cells may mediate the clinical efficacy of SES, at least in part. Sirolimus potentially may affect reendothelialization after stent implantation.

The Mechanism of In-Stent Restenosis in Radius Stent-An Experimental Porcine Study-

BACKGROUND

We investigated the mechanism of in-stent restenosis in radius stents in comparison to balloon-expandable stent (NIR stent) in pigs, with a focus on extracellular matrix (ECM).

METHODS AND RESULTS

Radius (n = 4) or NIR (n = 4) stents were implanted in the left coronary arteries of miniature pigs. Quantitative coronary ultrasound (QCU) was performed before, immediately after, and at 1 and 4 weeks after the implantation. The stented-coronary arteries were harvested at 4 weeks after the implantation followed by immunohistochemical, histological, reverse transcription-polymerase chain reaction (RT-PCR) and real-time PCR studies. In QCU, mean luminal areas at 4 weeks did not differ between both groups, whereas the mean stent area and neointimal area were significantly greater in the radius (p < 0.01). The immunohistochemical study revealed a significantly decreased number of neointimal macrophages and neovascularizations (p < 0.05, p < 0.01, respectively), and a stronger expression of tenascin-C in the radius. The histological study showed a larger ECM area and less neointimal cell density in the radius than in the NIR. The RT-PCR and real-time PCR analysis revealed an enhanced expression of tanascin-C mRNA in the radius than in the NIR.

CONCLUSIONS

Increased production of ECM, especially tenascin-C, played a greater role in the neointimal formation in the radius stent than inflammation.

Late thrombosis of sirolimus-eluting stents following noncardiac surgery

We describe two patients with in-stent thrombosis occurring 4 and 21 months after implantation of sirolimus-eluting stents. Both cases occurred following noncardiac surgery. In both cases, aspirin had been stopped prior to surgery. Both patient sustained a severe myocardial infarction; one died. The occurrence of late thrombosis of sirolimus-eluting stents is of concern.

Angiographic and Clinical Outcomes of a Pharmacokinetic Study of Sirolimus-Eluting Stents Lesson From Restenosis Cases

BACKGROUND

A pharmacokinetic (PK) study was conducted to evaluate sirolimus-eluting stents (SES) in Japanese people, representing the first clinical trial of the use of drug-eluting stents in Japan.

METHODS AND RESULTS

The PK study was conducted in 20 patients with 30 lesions treated with sirolimus-coated BX Velocity stents. All lesions were treated with a single SES (3 x 18 mm). Angiographic follow-up was performed at 8 months after SES implantation, and the clinical outcomes were evaluated at 1 year in all cases. All procedures were successful, and all patients were discharged without any adverse cardiac events. The total restenosis rate was 10% (3 lesions) and target vessel revascularization was performed in those 3 cases (15%). Restenoses occurred at the proximal and distal stent margins. Intravascular ultrasound examination of restenosis cases revealed abundant plaque burden at the stent edges even though the luminal area was preserved.

CONCLUSIONS

The sirolimus-eluting BX Velocity stent is safe and useful for Japanese patients with coronary artery disease. However, restenosis at proximal stent edge seems to be a problem.

Inflammation as a mechanism and therapeutic target for in-stent restenosis

Restenosis following coronary stenting has long been attributed to neointimal proliferation, thrombosis, and negative remodeling. More recently, the important role of inflammation in vascular healing has also been increasingly well understood. From animal models and from clinical experience, we know that endothelial injury, platelet and leukocyte interactions, and subcellular chemoattractant and inflammatory mediators are pivotal in the development of the inflammatory response following stent implantation. By examining the specific mechanisms governing the inflammatory response to percutaneous coronary intervention, we may gain insight into potential therapeutic targets and strategies to prevent restenosis in clinical practice.

Renin-Angiotensin System Intervention to Prevent In-Stent Restenosis

The occurrence of in-stent restenosis is a major drawback of percutaneous transluminal coronary angioplasty with stent placement. Target vessel revascularization is necessary in 15% of patients who receive a stent. Recent advances in the development of drug-eluting stents have reduced these numbers tremendously. However refinement of antirestenotic therapies remains obligatory. The emerging interest in more physiological antirestenotic therapies might unchain an interest in the well-known inhibitors of the rennin-angiotensin system (RAS), the angiotensin-converting enzyme inhibitors, and the angiotensin II type I receptor blockers. Contradictory results overshadow the discussion of whether intervention in the RAS could prevent in-stent restenosis. This review discusses the pathophysiology of in-stent restenosis, the role of the RAS in in-stent restenosis, and the possible role of RAS intervention in the prevention of in-stent restenosis.

Possible anaphylactic reaction to taxus stent: A case report

We report a patient who experienced an anaphylactic reaction during coronary artery stenting. Immediately after a polymer-based paclitaxel-eluting stent (Taxus, Boston-Scientific) is deployed, the patient developed profound hypotension and an erythematous rash. The case complicated with coronary spasm and a new thrombus formation making a second stent implantation necessary. The reaction was successfully reversed with epinephrine, steroid, antihistaminic, a 9-hr infusion of dopamine, and intraaortic balloon counterpulsation.

Initial and Follow-up Results of the BiodivYsio Phosphorylcholine Coated Stent for Treatment of Coronary Artery Disease

BACKGROUND

The BiodivYsio stent is coated with a phosphorylcholine containing copolymer to confer biocompatibility. The present study was designed to assess the safety and efficacy of this coronary stent for the treatment of native coronary artery lesions in patients with coronary artery disease.

METHODS AND RESULTS

From August 2001 to April 2003, 130 patients with lesions were treated with this stent. Elective stenting (ES) was performed in 90 patients and bailout stenting (BS) was performed in 40 patients with small vessels. Pre-interventional reference diameter, minimal lumen diameter (MLD), and lesion length were 2.68+/-0.51, 1.00+/-0.30, 12.78+/-4.32, respectively, and post-interventional MLD was 2.24+/-0.45 mm. The initial success rate was 100%. However, 2 non-Q-wave myocardial infarctions (non-QMI) occurred post-procedurally due to branch occlusion. A 6-month follow-up was performed. No subacute thrombosis occurred. In the ES group, 1 non-QMI occurred after the interventional procedure in another vessel. There was no death or coronary artery bypass grafting (CABG). The angiographic restenosis rate was 15.6%. In the BS group, there was no death, myocardial infarction or CABG. The angiographic restenosis rate was 17.5%.

CONCLUSION

The BiodivYsio stent is safe and effective as a primary device for the treatment of native coronary artery lesions, especially in small vessels.

Biomimetic actuators: where technology and cell biology merge

The structural and functional analysis of biological macromolecules has reached a level of resolution that allows mechanistic interpretations of molecular action, giving rise to the view of enzymes as molecular machines. This machine analogy is not merely metaphorical, as bio-analogous molecular machines actually are being used as motors in the fields of nanotechnology and robotics. As the borderline between molecular cell biology and technology blurs, developments in the engineering and material sciences become increasingly instructive sources of models and concepts for biologists. In this review, we provide a--necessarily selective--summary of recent progress in the usage of biological and biomimetic materials as actuators in artificial environments, focussing on motors built from DNA, classical cellular motor systems (tubulin/kinesin, actin/myosin), the rotary motor F1F0-ATPase and protein-based 'smart' materials.

Late thrombosis in cypher stents after the discontinuation of antiplatelet therapy

Drug-eluting stents, since their approval in the United States, have become the treatment of choice for de novo coronary artery narrowing due to their ability to reduce restenosis and the need for repeat revascularization. We present two patients who underwent percutaneous coronary intervention for the treatment of multivessel coronary artery disease; both patients were treated with sirolimus-eluting stents (SES) and bare metal stents (BMS).

Probucol Protects Against Smooth Muscle Cell Proliferation by Upregulating Heme Oxygenase-1

Background— Evidence suggests that induction of heme oxygenase-1 (HO-1) inhibits proliferation of vascular smooth muscle cells and intimal thickening after arterial injury, and therapeutic molecules induce HO-1. Probucol is the only oral drug that inhibits restenosis in humans and intimal thickening in animals, although its underlying mechanism remains unclear.

Methods and Results— Aortas were harvested from New Zealand White rabbits fed normal or 0.75% (wt/wt) probucol-fortified chow, with or without endothelial denudation of the abdominal aorta on day 21, and analyzed for heme oxygenase and apoptosis. Uninjured aortas were harvested on day 21 and balloon-injured aortas on days 22 and 25. Probucol significantly increased mRNA of HO-1 assessed by real-time PCR and HO activity in aortas at all time points. Probucol also enhanced apoptosis of medial cells in the injured aorta, as evidenced by the TUNEL assay. Furthermore, probucol (100 μmol/L) increased HO-1 mRNA and HO activity when added to rabbit aortic smooth muscle cells (RASMCs) cultured in serum-free medium for 24 hours. Induction of HO-1 mRNA was inhibited by actinomycin D and was associated with inhibition of RASMC proliferation. This probucol-induced increase in HO-1 mRNA and inhibition of RASMC proliferation was prevented by the HO inhibitor Sn(IV) protoporphyrin or transfection with small interference RNA (siRNA) to knockdown HO-1, but not by inactive Cu(II) protoporphyrin or scrambled siRNA.

Conclusions— Probucol induces HO-1, and this contributes to the inhibition of vascular SMC proliferation. This novel finding may explain how probucol inhibits restenosis and highlights HO-1 as a target for therapeutic intervention against occlusive vascular disease.

[Drug eluting stents: lessons from registries and literature]

Discussion about drug eluting stents (DES) was a highlight of the High Tech 2004 congress. This new kind of coronary stent represents a new revolution in the field of coronary angioplasty. After the excellent results with the bare metal stent compared with balloon angioplasty, concerning clinical events and restenosis in the 90s, DES have showed a spectacular decrease in restenosis rate. If it does not mean the end of restenosis, its decrease opens new therapeutic perspectives in percutaneous coronary intervention. A lot of registries and trials are now available and allow to assess the current use of DES, assess the incidence of (acute) stent thrombosis, assess the new therapeutic indications (intra-stent restenosis, left main coronary artery, chronic total occlusion, acute myocardial infarction...) and experimentations concerning evolution of the device are in process.

The molecular mechanisms of congenital hypofibrinogenaemia

Congenital hypofibrinogenaemia is characterized by abnormally low levels of fibrinogen and is usually caused by heterozygous mutations in the fibrinogen chain genes (alpha, beta and gamma). However, it does not usually result in a clinically significant condition unless inherited in a homozygous or compound heterozygous state, where it results in a severe bleeding disorder, afibrinogenaemia. Various protein and expression studies have improved our understanding of how mutations causing hypo- and afibrinogenaemia affect secretion of the mature fibrinogen molecule from the hepatocyte. Some mutations can perturb chain assembly as in the gamma153 Cys-->Arg case, while others such as the Bbeta Leu-->Arg and the Bbeta414 Gly-->Ser mutations allow intracellular hexamer assembly but inhibit protein secretion. An interesting group of mutations, such as gamma284 Gly-->Arg and gamma375 Arg-->Trp, not only cause hypofibrinogenaemia but are also associated with liver disease. The nonexpression of these variant chains in plasma fibrinogen is due to retention in the endoplasmic reticulum, which in turn leads to hypofibrinogenaemia.

Stent Thrombosis After Successful Sirolimus-Eluting Stent Implantation

BACKGROUND

Stent thrombosis (ST) is a rare but devastating complication of coronary stent implantation, occurring in 0.5% to 1.9% of patients with bare metal stents. The incidence of ST with drug-eluting stents is less well studied, particularly among patients outside of clinical trials.

METHODS AND RESULTS

The aim of this study was to evaluate the incidence and potential risk factors for ST in patients receiving sirolimus-eluting stents (SES) in the "real world" after commercial release in the United States in April 2003. All 652 patients who underwent SES implantation (776 lesions treated) at our institution between April and October 2003 were followed up prospectively after the procedure (median follow-up 100 days). During that period, 7 patients (1.1%, 95% CI 0.4% to 2.2%) developed ST within a range of 2 to 13 days, and 1 patient had an ST-elevation myocardial infarction on day 39 with evidence of thrombus within the SES at angiography. Patients with an ST had significantly smaller final nominal balloon diameters (2.75 versus 3.00 mm, P=0.04), and in 4 (57%) of the 7 patients with ST versus 1.7% of patients without ST (P<0.001), antiplatelet therapy had been discontinued after the procedure. Among the ST patients, 1 died and 5 had myocardial infarctions.

CONCLUSIONS

In this single-center experience, the incidence of ST after SES implantation was approximately 1%, which is within the expected range of bare metal stents. The discontinuation of antiplatelet therapy was strongly associated with the development of ST in this patient population.

Drug-Eluting Stents: Are They Really Safe?

Drug-eluting stents have reduced the frequency of in-stent restenosis. However, most of the results have been derived from simple lesions in noncomplex patients. In preclinical normal pig and rabbit studies, bare-metal stents show complete healing at 28 days, whereas drug-eluting stents show incomplete healing with persistence of fibrin and incomplete coverage of the stent struts by endothelial cells. In human beings similar delayed healing has been observed at 6 and 12 months in atherectomy specimens or at autopsy. The US Food and Drug Administration posted adverse event information for physicians regarding subacute thrombosis and hypersensitivity reaction following deployment of sirolimus-eluting stents in human beings. The authors have seen, at autopsy, late (18 months) stent thrombosis, aneurysm formation, and extensive inflammatory reaction limited to the arterial wall surrounding the stent that they interpret as a hypersensitivity reaction to the polymer. The authors advocate caution and aggressive use of nontoxic systemic drugs to prevent the complications of atherosclerosis along with better postmarket surveillance of patients and histologic examination of tissue from patients with drug-eluting stents.

An evidence-based approach to the use of drug-eluting stents in clinical practice

Less than a year after their release, drug-eluting stents are being used in more than 70% of patients who undergo percutaneous intervention for obstructive coronary disease in the United States. This unprecedented quick adoption was fueled by results of several randomized trials that demonstrated a profound reduction in restenosis rates compared with bare-metal stents. Subset analysis of the drug-eluting stent trials shows a strong restenosis reduction rate across a wide range of patient characteristics; however, these broad beneficial effects are based on randomized subjects who may not represent the actual population currently being treated with coronary stents. This review presents an analysis of the available data on the approved drug-eluting stents, including patient subsets that may or may not benefit; potential stent-specific complications; and a discussion of costs, risks, and cost-effectiveness.

From balloon angioplasty to drug-eluting stents: revolution or evolution?

Drug-eluting stenting is part of the evolution of interventional cardiology that started with Gruentzig's introduction of balloon angioplasty in 1977. Numerous advances in interventional cardiology technique have occurred since that time, and drug-eluting stents hold promise for reducing the restenosis rate but as yet have not been shown to influence survival or freedom from myocardial infarction. The ability of stents to influence these hard end points will be tested against the most difficult patient subset for interventional cardiology: persons with diabetes mellitus and multivessel disease. As more data are accumulated, prudent selective use of drug-eluting stenting seems most appropriate.