Effects of statins on six-month survival and clinical restenosis frequency after coronary stent deployment

Monocyte-mediated drug delivery systems for the treatment of cardiovascular diseases

Major advances have been achieved in understanding the mechanisms and risk factors leading to cardiovascular disorders and consequently developing new therapies. A strong inflammatory response occurs with a substantial recruitment of innate immunity cells in atherosclerosis, myocardial infarction, and restenosis. Monocytes and macrophages are key players in the healing process that ensues following injury. In the inflamed arterial wall, monocytes, and monocyte-derived macrophages have specific functions in the initiation and resolution of inflammation, principally through phagocytosis, and the release of inflammatory cytokines and reactive oxygen species. In this review, we will focus on delivery systems, mainly nanoparticles, for modulating circulating monocytes/monocyte-derived macrophages. We review the different strategies of depletion or modulation of circulating monocytes and monocyte subtypes, using polymeric nanoparticles and liposomes for the therapy of myocardial infarction and restenosis. We will further discuss the strategies of exploiting circulating monocytes for biological targeting of nanocarrier-based drug delivery systems for therapeutic and diagnostic applications.

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.

Stents and statins: history, clinical outcomes and mechanisms

The 1980s witnessed the inception of both stents and 3-hydroxy-3-methyl-glutaryl-CoA reductase inhibitors (statins). While they evolved separately, it was soon realized that they each offered a unique and powerful mechanism for targeting the major offender in cardiovascular disease, namely atherosclerosis. Coincidentally, the first statin was approved by the US FDA in 1987, the same year that the coronary stent was conceived. Since that time, stents and statins have revolutionized the field of cardiovascular medicine and their paths have been intertwined. Several pivotal randomized clinical trials have established statins as an effective therapy for improving clinical outcomes after percutaneous coronary intervention (PCI) among patients presenting with stable coronary artery disease and acute coronary syndromes. In addition, chronic statin therapy and acute loading of statins prior to PCI has consistently been shown to limit periprocedural myocardial necrosis. The mechanism for improved clinical outcomes with statins has clearly been associated with statin-induced reductions in LDL. In addition, statins may also exert 'pleiotropic' effects, independent of LDL lowering, that might counteract the inflammatory and prothrombotic mileu created with PCI. This article provides a brief historical perspective of the evolution of the use of statins and stents in patients with coronary artery disease, an evaluation of the available clinical data supporting the use of statins in patients undergoing PCI across a wide spectrum of clinical scenarios, and a discussion of the potential mechanisms of the benefit of statins in these patients.

Liposomal simvastatin attenuates neointimal hyperplasia in rats

Monocytes, macrophages, and inflammation play a key role in the process of neointimal proliferation and restenosis. The present study evaluated whether systemic and transient depletion of monocytes could be obtained by a single intravenous (IV) injection of simvastatin liposomes, for the inhibition of neointima formation. Balloon-injured carotid artery rats (n = 30) were randomly assigned to treatment groups of free simvastatin, simvastatin in liposomes (3 mg/kg), and saline (control). Stenosis and neointima to media ratio (N/M) were determined 14 days following single IV injection at the time of injury by morphometric analysis. Depletion of circulating monocytes was determined by flow cytometry analyzes of blood specimens. Inhibition of RAW264.7, J774, and THP-1 proliferation by simvastatin-loaded liposomes and free simvastatin was determined by the 3-(4, 5-dimethylthiazolyl-2)-2, 5- diphenyltetrazolium bromide assay. Simvastatin liposomes were successfully formulated and were found to be 1.5-2 times more potent than the free drug in suppressing the proliferation of monocytes/macrophages in cell cultures of RAW 264.7, J774, and THP-1. IV injection of liposomal simvastatin to carotid-injured rats (3 mg/kg, n = 4) resulted in a transient depletion of circulating monocytes, significantly more prolonged than that observed following treatment with free simvastatin. Administration to balloon-injured rats suppressed neointimal growth. N/M at 14 days was 1.56 +/- 0.16 and 0.90 +/- 0.12, control and simvastatin liposomes, respectively. One single systemic administration of liposomal simvastatin at the time of injury significantly suppresses neointimal formation in the rat model of restenosis, mediated via a partial and transient depletion of circulating monocytes.

Determinants of carotid endarterectomy anatomic durability: Effects of serum lipids and lipid-lowering drugs

OBJECTIVES

Carotid endarterectomy (CEA) remains the gold standard for treatment of carotid stenosis. With inevitable comparisons of catheter-based therapy to all aspects of CEA, this study of a large contemporary series was undertaken to evaluate the determinants of anatomic durability of CEA.

METHODS

During the interval (1989 through 1999), 2,127 primary, isolated CEAs with selective patching (50.2%) were performed in 1,853 patients (61.8% male, 36.1% symptomatic). End points included patient longevity and perioperative morbidity as well as evidence of CEA anatomic durability as defined by duplex evaluation: CEA restenosis (moderate, >50%, or greater recurrent stenosis), which included CEA anatomic failure (severe, >70%, restenosis/carotid occlusion). The incidence of CEA recurrent stenosis was temporally assessed early (<2 years) and late (>2 years) after operation. Clinical and surgical variables potentially associated with the study endpoints were analyzed by univariate and multivariate methods.

RESULTS

The perioperative stroke and death rate was 1.4% and the 2-year and 10-year survival was 88.1% and 44.9%, respectively. Anatomic failure after CEA developed in 3.9% at 2 years and in 8.5% at 5 years; only 3.2% of CEA patients underwent reoperation during a mean follow-up of 73.4 months. Early (<2 years) analysis revealed 12.2% restenosis, whereas late (>2 years) results identified 9.8% progression of carotid stenosis and a 5.8% rate of anatomic failure. Multivariate analysis determined elevated creatinine (odds ratio [OR], 1.719, P < .001) and female gender (OR, 1.564; P < .02) correlated with early restenosis. Surgical patch closure and lipid-lowering drugs were protective for both early restenosis, with ORs of 0.543 (P < .0.001) and 0.601 (P < .007) and early anatomic failure ORs of 0.469 (P < .02) and 0.517 (P < .03), respectively. Although only elevated serum cholesterol (OR, 1.009; P < .03) correlated with late anatomic failure, only lipid-lowering drugs were protective for both late freedom from progression of disease (OR, 0.202; P < .0002) or late CEA anatomic failure (OR, 0.128; P < .0003).

CONCLUSIONS

The association of female gender and elevated cholesterol with recurrent carotid stenosis is confirmed, elevated creatinine is introduced as a risk factor, and surgical patch repair is protective for early CEA recurrent carotid stenosis. The unique findings of the significant, beneficial effects of lipid-lowering drugs on both early and late CEA anatomic durability and patient survival indicate that such therapy should be instituted in most patients after CEA.

The drug-based pipeline against restenosis

More than 1 million percutaneous coronary interventions (PCIs) are performed yearly worldwide. Restenosis is the recurrent narrowing that can occur within 6 months following an initially successful PCI. Although drug-eluting stents have accomplished remarkable success, restenosis has not been eliminated and optimisation of both the polymers and drugs associated with them is desirable. This article reviews the presently available and potential preventive approaches against restenosis, including the sirolimus and paclitaxel drug-eluting stents.

Folate therapy and in-stent restenosis after coronary stenting

BACKGROUND

Vitamin therapy to lower homocysteine levels has recently been recommended for the prevention of restenosis after coronary angioplasty. We tested the effect of a combination of folic acid, vitamin B6, and vitamin B12 (referred to as folate therapy) on the risk of angiographic restenosis after coronary-stent placement in a double-blind, multicenter trial.

METHODS

A total of 636 patients who had undergone successful coronary stenting were randomly assigned to receive 1 mg of folic acid, 5 mg of vitamin B6, and 1 mg of vitamin B12 intravenously, followed by daily oral doses of 1.2 mg of folic acid, 48 mg of vitamin B6, and 60 microg of vitamin B12 for six months, or to receive placebo. The angiographic end points (minimal luminal diameter, late loss, and restenosis rate) were assessed at six months by means of quantitative coronary angiography.

RESULTS

At follow-up, the mean (+/-SD) minimal luminal diameter was significantly smaller in the folate group than in the placebo group (1.59+/-0.62 mm vs. 1.74+/-0.64 mm, P=0.008), and the extent of late luminal loss was greater (0.90+/-0.55 mm vs. 0.76+/-0.58 mm, P=0.004). The restenosis rate was higher in the folate group than in the placebo group (34.5 percent vs. 26.5 percent, P=0.05), and a higher percentage of patients in the folate group required repeated target-vessel revascularization (15.8 percent vs. 10.6 percent, P=0.05). Folate therapy had adverse effects on the risk of restenosis in all subgroups except for women, patients with diabetes, and patients with markedly elevated homocysteine levels (15 micromol per liter or more) at baseline.

CONCLUSIONS

Contrary to previous findings, the administration of folate, vitamin B6, and vitamin B12 after coronary stenting may increase the risk of in-stent restenosis and the need for target-vessel revascularization.

C-reactive protein and myocardial infarction during percutaneous coronary intervention

OBJECTIVE

To evaluate the prognostic information of preprocedural C-reactive protein (CRP) levels in serum to predict myocardial infarction during percutaneous coronary interventions (PCI).

DESIGN

Prospective study.

SETTING

University hospital.

PATIENTS

A total of 400 consecutive patients with normal serum troponin T levels (</=0.03 microg L-1) presenting with stable or unstable angina pectoris.

INTERVENTIONS

PCI.

MAIN OUTCOME MEASURES

C-reactive protein levels in serum measured by a high sensitive method. Myocardial infarction defined as a serum troponin T elevation the day after PCI to a level >0.05 microg L-1.

RESULTS

Eighty-three patients (21%) experienced a myocardial infarction during PCI. The median value of CRP before the procedure was 1.83 (0.12-99.7) mg L-1. No difference was seen in CRP levels before PCI between patients without or with myocardial infarction during PCI. Multivariate analysis identified stent implantation (OR 2.68, 95% CI 1.18-7.28, P = 0.03), procedure time (OR 2.15, 95% CI 1.28-3.67, P < 0.005) and complications during the procedure (OR 3.62, 95% CI 1.72-7.58, P < 0.001) as independent predictors of myocardial infarction during PCI.

CONCLUSION

Increased CRP levels in serum before PCI were not associated with myocardial infarction during the procedure. Furthermore, patients with an expected long procedure and a high probability of stent implantation have an increased risk of developing myocardial infarction during PCI. This finding may be useful to help the operator to decide the antithrombotic regime before, during and after the procedure and the need for observation after the procedure.

The cardioprotective effects of statins

In addition to their lipid-modulating properties, statins have a large number of beneficial cardiovascular effects that have emerged over time and that were not anticipated during drug development. The lipid and nonlipid effects act in a concerted way to reduce the ischemic burden of the myocardium and to protect it against injury. By acting on the vessel wall, statins may prevent lesion initiation and repair injuries, enhance myocardial perfusion, slow lesion progression, and prevent coronary occlusion. They may also directly reduce myocardial damage, favor myocardial repair, and protect against immune injury. This review focuses on properties of statins that contribute to their cardioprotective effect. The first section includes information on modulation of vascular tone, endothelial permeability and function, inhibition of complement injury, curbing of foam cell formation, antioxidant and anti-inflammatory properties, and profibrinolytic and anticoagulant activities. The second section relates to reduction of myocardial necrosis, myocardial hypertrophy, blood pressure, and heart failure, as well as mobilization of endothelial progenitor cells for repair, angiogenic effects, and immunomodulation. In many instances, results of in vitro and animal studies have raised expectations and prompted studies in humans. Several clinical trials have confirmed these expectations and have strengthened the value of statins as valuable antiatherosclerotic and cardioprotective agents.

Pharmacologic prevention of both restenosis and atherosclerosis progression: AGI-1067, probucol, statins, folic acid and other therapies

PURPOSE OF REVIEW

In this article, the authors intend to provide an update on clinical trials of pharmacologic prevention of restenosis after percutaneous coronary interventions, placed in the perspective of the use of orally administered therapy for the prevention of atherosclerosis progression and clinical events.

RECENT FINDINGS

AGI-1067, the mono-succinic acid ester of probucol, is a phenolic antioxidant member of a novel class of agents termed v-protectants. It has strong antioxidant properties equipotent to those of probucol and antiinflammatory properties. It inhibits gene expression of VCAM-1 and MCP-1 and has been effective at preventing atherosclerosis in all tested animal models including the non-human primate. In the Canadian Antioxidant Restenosis Trial (CART) 1, AGI-1067 and probucol improved lumen dimensions at the site of percutaneous coronary intervention. AGI-1067 also improved luminal dimensions of non-intervened coronary reference segments in the Canadian Antioxidant Restenosis Trial, which suggests a direct antiatherosclerosis effect. Probucol reduced post-percutaneous coronary intervention restenosis and progression of carotid atherosclerosis in other clinical trials. Although statins reduce atherosclerotic events, they do not appear to have a significant effect on restenosis. The failure of folate therapy to protect against restenosis in the Folate After Coronary Intervention Trial (FACIT) occurred despite significant reductions in homocysteine levels.

SUMMARY

Prevention of both post-percutaneous coronary intervention restenosis and atherosclerosis progression with a pharmacologic agent such as AGI-1067 may be an attractive treatment paradigm. Two important trials that test the antioxidant/antiinflammatory hypothesis are ongoing with AGI-1067: the Canadian Atherosclerosis and Restenosis Trial 2, which assesses its value for the reduction of both atherosclerosis progression and post-percutaneous coronary interventions restenosis, and the Aggressive Reduction of Inflammation Stops Events (ARISE) trial which is evaluating its effects on cardiovascular events.