Usefulness of fish oil supplements in preventing clinical evidence of restenosis after percutaneous transluminal coronary angioplasty

Protection from procedural myocardial injury by omega-3 polyunsaturated fatty acids (PUFAs): is related with lower levels of creatine kinase-MB (CK-MB) and troponin I?

OBJECTIVE

This study sought to investigate the effect of omega-3 polyunsaturated fatty acids (PUFAs) on cardiac biomarkers, CK-MB, and troponin I in patients undergoing PCI.

BACKGROUND

Restenosis remains as a major long-term complication following percutaneous coronary intervention (PCI). It appears that there is strong relationship between post-PCI creatine kinase-MB (CK-MB) and troponin I elevation and cardiovascular events after PCI.

METHODS

In this randomized clinical trial, a total of 90 patients planned to undergo PCI were randomly assigned into two groups: Group A-receiving omega-3 PUFAs (3 g, 12 h before PCI) plus standard treatment (n = 43) and Group B-control group, receiving only standard therapy (n = 47). Standard treatment included aspirin 325 mg and clopidogrel 600 mg loading dose. The plasma CK-MB level was measured before the procedure (baseline), at 8 and 24 h after PCI. The plasma troponin I was measured at baseline and 24 h after PCI.

RESULTS

In comparison with control, omega-3 PUFAs could significantly reduce the level of CK-MB in 8 (P = 0.001) and 24 h (P = 0.012) after its prescription in the omega-3 PUFAs group. Omega-3 PUFAs could not significantly decrease troponin I.

CONCLUSION

Our results revealed that omega-3 PUFAs can be considered as a safe adjunctive medication to the standard regimen before PCI for the aim of decreasing cardiovascular event after PCI.

Omega-3 fatty acids in high-risk cardiovascular patients: a meta-analysis of randomized controlled trials

BACKGROUND

Multiple randomized controlled trials (RCTs) have examined the cardiovascular effects of omega-3 fatty acids and have provided unexplained conflicting results. A meta-analysis of these RCTs to estimate efficacy and safety and potential sources of heterogeneity may be helpful.

METHODS

The Cochrane library, MEDLINE, and EMBASE were systematically searched to identify all interventional trials of omega-3 fatty acids compared to placebo or usual diet in high-risk cardiovascular patients. The primary outcome was all-cause mortality and secondary outcomes were coronary restenosis following percutaneous coronary intervention and safety. Meta-analyses were carried out using Bayesian random-effects models, and heterogeneity was examined using meta-regression.

RESULTS

A total of 29 RCTs (n = 35,144) met our inclusion criteria, with 25 reporting mortality and 14 reporting restenosis. Omega-3 fatty acids were not associated with a statistically significant decreased mortality (relative risk [RR] = 0.88, 95% Credible Interval [CrI] = 0.64, 1.03) or with restenosis prevention (RR = 0.89, 95% CrI = 0.72, 1.06), though the probability of some benefit remains high (0.93 and 0.90, respectively). However in meta-regressions, there was a >90% probability that larger studies and those with longer follow-up were associated with smaller benefits. No serious safety issues were identified.

CONCLUSIONS

Although not reaching conventional statistical significance, the evidence to date suggests that omega-3 fatty acids may result in a modest reduction in mortality and restenosis. However, caution must be exercised in interpreting these benefits as results were attenuated in higher quality studies, suggesting that bias may be at least partially responsible. Additional high quality studies are required to clarify the role of omega-3 fatty acid supplementation for the secondary prevention of cardiovascular disease.

Effect of fish oil on arrhythmias and mortality: systematic review

OBJECTIVE

To synthesise the literature on the effects of fish oil-docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA)-on mortality and arrhythmias and to explore dose response and formulation effects.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Medline, Embase, the Cochrane Library, PubMed, CINAHL, IPA, Web of Science, Scopus, Pascal, Allied and Complementary Medicine, Academic OneFile, ProQuest Dissertations and Theses, Evidence-Based Complementary Medicine, and LILACS. Studies reviewed Randomised controlled trials of fish oil as dietary supplements in humans.

DATA EXTRACTION

The primary outcomes of interest were the arrhythmic end points of appropriate implantable cardiac defibrillator intervention and sudden cardiac death. The secondary outcomes were all cause mortality and death from cardiac causes. Subgroup analyses included the effect of formulations of EPA and DHA on death from cardiac causes and effects of fish oil in patients with coronary artery disease or myocardial infarction.

DATA SYNTHESIS

12 studies totalling 32 779 patients met the inclusion criteria. A neutral effect was reported in three studies (n=1148) for appropriate implantable cardiac defibrillator intervention (odds ratio 0.90, 95% confidence interval 0.55 to 1.46) and in six studies (n=31 111) for sudden cardiac death (0.81, 0.52 to 1.25). 11 studies (n=32 439 and n=32 519) provided data on the effects of fish oil on all cause mortality (0.92, 0.82 to 1.03) and a reduction in deaths from cardiac causes (0.80, 0.69 to 0.92). The dose-response relation for DHA and EPA on reduction in deaths from cardiac causes was not significant.

CONCLUSIONS

Fish oil supplementation was associated with a significant reduction in deaths from cardiac causes but had no effect on arrhythmias or all cause mortality. Evidence to recommend an optimal formulation of EPA or DHA to reduce these outcomes is insufficient. Fish oils are a heterogeneous product, and the optimal formulations for DHA and EPA remain unclear.

Expert opinion: omega-3 fatty acids and bleeding-cause for concern?

Omega-3 fatty acid ethyl esters have well-known triglyceride-lowering properties and were shown >30 years ago to inhibit platelet function. With the recent US Food and Drug Administration (FDA) approval of these agents for treating severe triglyceride elevations, concerns about excess bleeding naturally arise. However, an objective assessment of the evidence for clinically significant bleeding reveals that such concerns are unfounded. As such, the benefits of triglyceride lowering with omega-3 fatty acids more than outweigh any theoretical risks for increased bleeding.

Antiatherogenic effects of n-3 fatty acids - evidence and mechanisms

N-3 (omega-3) (polyunsaturated) fatty acids are thought to display a variety of beneficial effects for human health. Clues to the occurrence of cardiovascular protective effects have been, however, the spur for the first biomedical interest in these compounds, and are the best documented. Historically, the epidemiologic association between dietary consumption of n-3 fatty acids and cardiovascular protection was first suggested by Bang and Dyerberg, who identified the high consumption of fish, and therefore, of fish oil-derived n-3 fatty acids, as the likely explanation for the strikingly low rate of coronary heart disease events reported in the Inuit population. Since their initial reports, research has proceeded in parallel to provide further evidence for their cardioprotection and to understand underlying mechanisms. Decreased atherogenesis is currently thought to be a part of the cardiovascular protection by n-3 fatty acids. This article summarizes the evidence for such a claim and the mechanisms putatively involved.

n-3 Fatty acids from fish or fish-oil supplements, but not alpha-linolenic acid, benefit cardiovascular disease outcomes in primary- and secondary-prevention studies: a systematic review

Studies on the relation between dietary n-3 fatty acids (FAs) and cardiovascular disease vary in quality, and the results are inconsistent. A systematic review of the literature on the effects of n-3 FAs (consumed as fish or fish oils rich in eicosapentaenoic acid and docosahexaenoic acid or as alpha-linolenic acid) on cardiovascular disease outcomes and adverse events was conducted. Studies from MEDLINE and other sources that were of > or =1 y in duration and that reported estimates of fish or n-3 FA intakes and cardiovascular disease outcomes were included. Secondary prevention was addressed in 14 randomized controlled trials (RCTs) of fish-oil supplements or of diets high in n-3 FAs and in 1 prospective cohort study. Most trials reported that fish oil significantly reduced all-cause mortality, myocardial infarction, cardiac and sudden death, or stroke. Primary prevention of cardiovascular disease was reported in 1 RCT, in 25 prospective cohort studies, and in 7 case-control studies. No significant effect on overall deaths was reported in 3 RCTs that evaluated the effects of fish oil in patients with implantable cardioverter defibrillators. Most cohort studies reported that fish consumption was associated with lower rates of all-cause mortality and adverse cardiac outcomes. The effects on stroke were inconsistent. Evidence suggests that increased consumption of n-3 FAs from fish or fish-oil supplements, but not of alpha-linolenic acid, reduces the rates of all-cause mortality, cardiac and sudden death, and possibly stroke. The evidence for the benefits of fish oil is stronger in secondary- than in primary-prevention settings. Adverse effects appear to be minor.

Effects of omega-3 fatty acids on coronary restenosis, intima–media thickness, and exercise tolerance: A systematic review

Greater omega-3 fatty acid consumption is associated with reduced cardiovascular disease risk. Though the mechanisms of their effect are unclear, they may involve lesion formation and heart function. We conducted a systematic review of the clinical literature on the effect of omega-3 fatty acids on measures of vascular structure and function. We included studies that assessed fish and plant sources of omega-3 fatty acids on coronary artery restenosis after angioplasty, carotid IMT, and exercise capacity. Compared to placebo, the summary risk ratio of coronary artery restenosis with fish oil is 0.87 (95% CI 0.73, 1.05) across 12 randomized controlled trials. Two prospective studies reported increased carotid IMT, whereas two cross-sectional studies reported a reduction of IMT, with fish, fish oil or ALA consumption. Three randomized trials and three uncontrolled studies reported small non-significant improvements in exercise capacity with fish oil. Overall, little or no effect of fish oil was found for a variety of markers of cardiovascular disease risk. There are insufficient studies to draw conclusions about the effect of ALA. The dearth of long term data on fish consumption or omega-3 fatty acid supplementation on measures of cardiovascular disease risk severely limits our ability to draw definitive conclusions at this time.

Fish oils in the care of coronary heart disease patients: a meta-analysis of randomized controlled trials

What is the place of fish oils in the care of coronary heart disease (CHD) patients? As several clinical trials have already addressed this question without giving definitive answers, we did a meta-analysis of trials regarding the efficacy of omega-3 fatty acids in preventing cardiovascular mortality and morbidity. We searched the MEDLINE (1966-2003), EMBASE databases, proceedings abstracts and references of reviewed articles. Randomized controlled trials (RCTs) of the efficacy of omega-3 fatty acids among adults with recent or acute myocardial infarction (MI), or angina were selected. Two reviewers abstracted data independently. Five relevant outcomes, mortality from all causes, fatal and non-fatal MI, non-fatal stroke and angina, were measured. Data were synthesized using a fixed effect model. Ten RCTs with 14,727 patients were included. No significant heterogeneity was detected. Daily intake of omega-3 fatty acids for a mean duration of 37 months decreased all causes of mortality by 16% (relative risk 0.84, 95% confidence interval [0.76; 0.94]) and the incidence of death due to MI by 24% (0.76, [0.66; 0.88]). No significant effect was found for the other outcomes. Because of the suboptimal quality of the studies included into the meta-analysis and the absence of data in patients receiving statins, these results do not justify adding fish oils systematically to the heavy pharmaceutical assortment already recommended in CHD patients.

Effects of omega-3 fatty acids on cytokines and adhesion molecules

The dietary intake of omega-3 (n-3) polyunsaturated fatty acids has emerged, over the past 20 years, as an important way to modify cardiovascular risk. This likely occurs through beneficial effects at all stages in the natural history of vascular disease, from the inception of atherosclerotic lesions, to their growth and acute complications (plaque rupture in most instances), up to protection of myocardium from the consequences of ensuing acute myocardial ischemia. This review specifically focuses on the modulating effects of n-3 fatty acids on biologic events involved in early atherogenesis, including important properties of these natural substances on endothelial expression of adhesion molecules and cytokines, processes collectively denoted as "endothelial activation." By decreasing the endothelial responsiveness to proinflammatory and proatherogenic stimuli, n-3 fatty acids act on molecular events not targeted by any other drugs or interventions, and thereby complementary to those of already implemented pharmacologic treatments.

Omega 3 fatty acids for prevention and treatment of cardiovascular disease

BACKGROUND

It has been suggested that omega 3 (W3, n-3 or omega-3) fats from oily fish and plants are beneficial to health.

OBJECTIVES

To assess whether dietary or supplemental omega 3 fatty acids alter total mortality, cardiovascular events or cancers using both RCT and cohort studies.

SEARCH STRATEGY

Five databases including CENTRAL, MEDLINE and EMBASE were searched to February 2002. No language restrictions were applied. Bibliographies were checked and authors contacted.

SELECTION CRITERIA

RCTs were included where omega 3 intake or advice was randomly allocated and unconfounded, and study duration was at least six months. Cohorts were included where a cohort was followed up for at least six months and omega 3 intake estimated.

DATA COLLECTION AND ANALYSIS

Studies were assessed for inclusion, data extracted and quality assessed independently in duplicate. Random effects meta-analysis was performed separately for RCT and cohort data.

MAIN RESULTS

Forty eight randomised controlled trials (36,913 participants) and 41 cohort analyses were included. Pooled trial results did not show a reduction in the risk of total mortality or combined cardiovascular events in those taking additional omega 3 fats (with significant statistical heterogeneity). Sensitivity analysis, retaining only studies at low risk of bias, reduced heterogeneity and again suggested no significant effect of omega 3 fats. Restricting analysis to trials increasing fish-based omega 3 fats, or those increasing short chain omega 3s, did not suggest significant effects on mortality or cardiovascular events in either group. Subgroup analysis by dietary advice or supplementation, baseline risk of CVD or omega 3 dose suggested no clear effects of these factors on primary outcomes. Neither RCTs nor cohorts suggested increased relative risk of cancers with higher omega 3 intake but estimates were imprecise so a clinically important effect could not be excluded.

REVIEWERS' CONCLUSIONS

It is not clear that dietary or supplemental omega 3 fats alter total mortality, combined cardiovascular events or cancers in people with, or at high risk of, cardiovascular disease or in the general population. There is no evidence we should advise people to stop taking rich sources of omega 3 fats, but further high quality trials are needed to confirm suggestions of a protective effect of omega 3 fats on cardiovascular health. There is no clear evidence that omega 3 fats differ in effectiveness according to fish or plant sources, dietary or supplemental sources, dose or presence of placebo.

n-3 fatty acids: antiatherosclerotic effects

The low incidence of cardiovascular disease associated epidemiologically with high consumption of food rich in n-3 fatty acids suggests the possibility that part of the beneficial cardiovascular effects of these natural substances may be due to a reduction of atherosclerosis. This has been recently confirmed in autoptic data and in at least one prospective trial evaluating the progression of coronary atherosclerosis in humans. This paper reviews published literature on n-3 fatty acids and atherosclerosis in animal models and in humans and in vitro experimental data yielding suport to the hypothesis of antiatherosclerotic effects of these substances.

Prevention of postcoronary angioplasty restenosis by omega-3 fatty acids: main results of the Esapent for Prevention of Restenosis ITalian Study (ESPRIT)

BACKGROUND AND OBJECTIVE

Previous trials of omega-3 fatty acids (omega-3 FA) for restenosis prevention after percutaneous transluminal coronary angioplasty (PTCA) have yielded conflicting results. We tested the hypothesis that long-term administration of omega-3 FA before PTCA may have significant effects on restenosis.

METHODS

We randomized 339 patients in a double-blind, placebo-controlled study of omega-3 FA (as an ethyl ester preparation given as 6 1-g capsules providing 3 g eicosapentaenoic acid and 2.1 g docosahexaenoic acid/d started 1 month before PTCA and given for 1 month thereafter, then continued at half-dose for 6 months) versus an olive oil placebo. Of these, 257 patients (125 on omega-3 FA, 132 on placebo) well matched for risk factors underwent successful balloon-only PTCA (280 total lesions) and were evaluable at 6 months with repeat angiography. Restenosis was defined at quantitative angiography as a recurrence of >50% diameter stenosis in the dilated vessel (Definition I) and as >50% loss of the short-term gain immediately after PTCA (Definition II).

RESULTS

Restenosis rates per vessel were 29.4% and 31.6% in the omega-3 FA group, and 39.6% and 35.4% in the placebo group according to Definitions I (P =.04) and II (P = not significant), respectively. Restenosis rates per patient were 31.2% and 33.6% in the omega-3 FA group, and 40.9% and 37.1% in the placebo group according to Definitions I (P =.05) and II (P = not significant), respectively.

CONCLUSIONS

With a long treatment before PTCA, omega-3 FA produced a small but significant decrease in the restenosis rate compared with placebo.

Fish oil supplementation prevents neointima formation in nonhypercholesterolemic balloon-injured rabbit carotid artery by reducing medial and adventitial cell activation

We asked whether balloon-injured neointima formation in the presence of high/low serum cholesterol (CT) levels might be affected by dietary supplementation with fish oil (FO). To test this hypothesis, we examined the differentiation, proliferation, or apoptosis profile of smooth muscle cell (SMC) and adventitial cell response to a mild injury induced via a Fogarty catheter in the carotid artery of adult rabbits that had been fed a standard chow or 0.5% CT-enriched diet starting 4 weeks before the lesion. One week before surgery, animals received FO supplementation. This regimen was continued for the following 3 weeks. The effect of FO on the early proliferative/migratory response of carotid SMCs was also examined in 2- and 7-day-injured normocholesterolemic rabbits. As controls, animals subjected to 3-week endothelial injury and animals kept on a 7-week CT diet were used. Carotid cryosections from the various animal groups were evaluated for morphometry (image analysis), differentiation (immunofluorescence with monoclonal antibodies specific for smooth muscle markers, ie, myosin isoforms, SM22, and fibronectin), proliferation (bromodeoxyuridine incorporation), and apoptosis (terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling). FO treatment significantly reduced the development of intimal thickening in normocholesterolemic rabbits but had no efficacy in the presence of relatively higher serum CT levels. At day 2 (adventitia) and day 7 (neointima, media, and adventitia), the proliferation index of SMCs in FO-treated injured rabbits was markedly lower than in untreated injured controls. Concomitantly with the antiproliferative effect, FO was able to decrease the size of 2 cell types involved in the cell growth response to endothelial injury, namely, the "fetal-type" medial SMC subpopulation and the fibroblast-derived adventitial myofibroblasts. Thus, in our experimental conditions, a low CT level is a permissive condition for FO to prevent neointima formation to a considerable extent. This event is attributable to the early postinjury effect of FO on SMC/adventitial cell proliferation/differentiation patterns.

N-3 fatty acids do not prevent restenosis after coronary angioplasty: results from the CART study. Coronary Angioplasty Restenosis Trial

OBJECTIVES

The aim of the study was to investigate whether omega-3 fatty acids (n-3 FA) reduce the occurrence of restenosis after percutaneous transluminal coronary angioplasty.

BACKGROUND

Meta-analyses have shown significant reduction of restenosis after coronary angioplasty upon supplementation with n-3 FA.

METHODS

In a prospective, placebo-controlled, double-blind study, 500 patients were randomly allocated to treatment with n-3 FA (Omacor, Pronova AS, Oslo, Norway) 5.1 g/day or corn oil (placebo) starting at least two weeks prior to elective coronary angioplasty. The treatment was continued until restenosis evaluation by quantitative coronary angiography after six months. Stenosis was defined as a minimal luminal diameter (MLD) < 40% of the reference diameter. Successful coronary angioplasty was defined as > or = 20% acute gain in MLD and a residual stenosis < 50%. Restenosis was defined as > or = 20% late loss of diameter and stenosis > 50% or an increase in stenosis of > or = 0.7 mm. Three-hundred ninety-two patients fulfilled the criteria for initial stenosis and successful coronary angioplasty, and, except four patients who died, none were lost for follow-up.

RESULTS

Restenosis occurred in 108/266 (40.6%) of the treated stenoses in the Omacor group and in 93/263 (35.4%) in the placebo group (odds ratio [OR] 1.25, 95% confidence interval [CI] [0.87-1.80] p = 0.21). In the Omacor group one or more restenoses occurred in 90/196 (45.9%) patients as compared with 86/192 (44.8%) in the placebo group (OR 1.05, 95% CI [0.69-1.59] p = 0.82).

CONCLUSIONS

Supplementation with 5.1 g n-3 FA/day for six months, initiated at least two weeks prior to coronary angioplasty did not reduce the incidence of restenosis.

Effect of pravastatin on angiographic restenosis after coronary balloon angioplasty. The PREDICT Trial Investigators. Prevention of Restenosis by Elisor after Transluminal Coronary Angioplasty

OBJECTIVES

This study sought to determine whether pravastatin affects clinical or angiographic restenosis after coronary balloon angioplasty.

BACKGROUND

Experimental data and preliminary clinical studies suggest that lipid-lowering drugs might have a beneficial effect on restenosis after coronary angioplasty.

METHODS

In a multicenter, randomized, double-blind trial, 695 patients were randomized to receive pravastatin (40 mg/day) or placebo for 6 months after successful balloon angioplasty. All patients received aspirin (100 mg/day). The primary angiographic end point was minimal lumen diameter (MLD) at follow-up, assessed by quantitative coronary angiography. A sample size of 313 patients per group was required to demonstrate a difference of 0.13 mm in MLD between groups (allowing for a two-tailed alpha error of 0.05 and a beta error of 0.20). To allow for incomplete angiographic follow-up (estimated lost to follow-up rate of 10%), 690 randomized patients were required. Secondary end points were angiographic restenosis rate (restenosis assessed as a categoric variable, > 50% stenosis) and clinical events (death, myocardial infarction, target vessel revascularization).

RESULTS

At baseline, clinical, demographic, angiographic and lipid variables did not differ significantly between groups. In patients treated with pravastatin, there was a significant reduction in total and low density lipoprotein cholesterol and triglyceride levels and a significant increase in high density lipoprotein cholesterol levels. At follow-up the MLD (mean +/- SD) was 1.47 +/- 0.62 mm in the placebo group and 1.54 +/- 0.66 mm in the pravastatin group (p = 0.21). Similarly, late loss and net gain did not differ significantly between groups. The restenosis rate (recurrence > 50% stenosis) was 43.8% in the placebo group and 39.2% in the pravastatin group (p = 0.26). Clinical restenosis did not differ significantly between groups.

CONCLUSIONS

Although pravastatin has documented efficacy in reducing clinical events and angiographic disease progression in patients with coronary atherosclerosis, this study shows that it has no effect on angiographic outcome at the target site 6 months after coronary angioplasty.

Fish oils and low-molecular-weight heparin for the reduction of restenosis after percutaneous transluminal coronary angioplasty. The EMPAR Study

BACKGROUND

Percutaneous transluminal coronary angioplasty (PTCA) is complicated by restenosis within 6 months in > 40% of patients. Theoretical, animal experimental, and human epidemiological and clinical trial findings have suggested that fish oils (n-3) might reduce restenosis. Low-molecular-weight heparin (LMWH) has reduced cellular proliferation and restenosis in several experimental systems.

METHODS AND RESULTS

We randomized 814 patients to fish oils (5.4 g n-3 fatty acids) or placebo a median of 6 days before PTCA and continued for 18 weeks. At the time of sheath removal, 653 patients with at least one successfully dilated lesion were randomized to LMWH (30 mg SC BID) or control for 6 weeks in a 2 x 2 factorial design. Follow-up with quantitative coronary angiography (QCA; target, 18 weeks) was interpretable on 96% of these patients. Restenosis rates per patient were for n-3, 46.5%; placebo, 44.7%; LMWH, 45.8%; and control, 45.4%. Restenosis rates per lesion were for n-3, 39.7%; placebo, 38.7%; LMWH, 38%; and control, 40.4%. At follow-up QCA, mean minimal lumen diameters were (mm) for n-3, 1.12; placebo, 1.10; LMWH, 1.12; and control, 1.10. Fifteen percent of patients permanently discontinued n-3/placebo before study completion, and 21% of patients discontinued LMWH early. There were no significant differences in the occurrences of ischemic events. Bleeding was more common with LMWH, usually was mild, and led to early discontinuation of study medication in only 0.9% of patients. Gastrointestinal side effects were more common in patients receiving n-3 than placebo.

CONCLUSIONS

There is no evidence for a clinically important reduction of PTCA restenosis in this trial by either n-3 or LMWH. Evaluation of the results for n-3 in the context of previously published data on the reduction of PTCA restenosis indicates that n-3 is not efficacious and that further trials are unwarranted.

Restenosis--an open file

The main procedural drawback to percutaneous coronary angioplasty is restenosis of the treated site within 6 months. Despite advances in equipment, technique, and adjunctive therapies, restenosis has occurred in approximately one-third to one-half of all patients. The biology of restenosis can be divided into plaque persistence and recoil, thrombus formation and transformation, and cellular proliferation and vascular remodeling. Animal models of restenosis have helped to elucidate these mechanisms of restenosis and provide a means to test pharmacologic and mechanical strategies to reduce stenosis recurrence. While numerous agents have been tested in animal models, until recently none has translated into benefit in large-scale clinical trials. Two therapeutic "hopefuls" which have recently emerged in clinical practice are the potent platelet inhibitors, glycoprotein IIb/IIIa receptor antagonists, and intracoronary metallic stents. The IIb/IIIa receptor antagonists target thrombus formation at the angioplasty site, thereby minimizing abrupt vessel closure acutely and neointimal growth chronically, while intracoronary stents safely produce a large coronary arterial lumen acutely and prevent vessel recoil. Separately, these therapeutic strategies have been shown to reduce clinical restenosis 20-30% at 6-month follow-up. With these encouraging results, the future will certainly provide more pharmacologic and mechanical therapies targeting restenosis. With increased understanding of the restenotic process and continued refinement of effective treatments, it may be possible one day to prevent stenosis recurrence.

Fish oil treatment decreases superoxide anions in the myocardium and coronary arteries of atherosclerotic monkeys

BACKGROUND

This experiment sought to determine the effects of fish oil on superoxide anion production in the myocardium and coronary arteries of atherosclerotic monkeys. Recent evidence indicates that dietary supplementation with fish oil preserves normal vasomotion of atherosclerotic coronary arteries and reduces damage to the myocardium after ischemia and reperfusion, although the mechanisms remain unclear.

METHODS AND RESULTS

Adult male cynomolgus monkeys were fed an atherogenic diet with (n = 15) or without (n = 15) half the fat calories from fish oil. After 12 months, chemiluminescence of lucigenin was used to measure superoxide anion production in coronary arteries and myocardium after 1 hour of ischemia and 2 hours of reperfusion. The signals were calibrated with known quantities of xanthine and xanthine oxidase. Superoxide anion production in ischemic myocardium was (mean +/- SEM, nmol/mg dry wt per minute) 1 +/- 1 and 4 +/- 1 in monkeys fed fish oil and not fed fish oil, respectively (P < .05). Superoxide anion production in coronary arteries not exposed to ischemia and reperfusion was (nmol/mg dry wt per minute) 4 +/- 1 and 8 +/- 2 in monkeys fed fish oil and not fed fish oil, respectively (P < .05). Superoxide anion production in coronary arteries was (nmol/mg dry wt per minute) 5 +/- 2 and 16 +/- 3 in monkeys fed fish oil and not fed fish oil after ischemia and reperfusion, respectively (P < .05).

CONCLUSIONS

Dietary supplementation with fish oil reduced vascular superoxide anion production and prevented the increase in vascular and myocardial superoxide anion production that accompanied ischemia and reperfusion. These phenomena may underlie some of the beneficial cardiovascular effects of fish oil.

Experimental therapeutics and clinical studies in (re)stenosis

Restenosis is defined functionally as loss of luminal vessel patency following various methods of interventional cardiology, but ultrastructurally, it represents a wound healing response that involves smooth muscle migration, proliferation and matrix deposition at the site of injury. Currently, despite intensive experimental and clinical studies, there are no therapeutic agents that are able to suppress pharmacologically the clinical restenosis. Ultrastructural pathology and animal modeling have played a pivotal role in defining new experimental therapies and rationales for clinical trials. However, concerns regarding the lack of suitable animal models persist and of the many compounds reported efficacious preclinically, none have demonstrated clinical benefit in preventing restenosis. Animal modeling studies now include the use of true restenosis studies, which may be more clinically relevant and pharmacologically predictive of clinical performance.

Lack of effect of lovastatin on restenosis after coronary angioplasty. Lovastatin Restenosis Trial Study Group

BACKGROUND

Experimental and clinical observations suggest that lowering serum lipid levels may reduce the risk of restenosis after coronary angioplasty. We report the results of a prospective, randomized, double-blind trial evaluating whether lowering lipid levels with lovastatin can prevent or delay restenosis after angioplasty.

METHODS

Seven to 10 days before angioplasty, we randomly assigned eligible patients to receive lovastatin (40 mg orally twice daily) or placebo. Patients who underwent successful, complication-free, first-time angioplasty of a native vessel (the index lesion) continued to receive therapy for six months, when a second coronary angiogram was obtained. The primary end point was the extent of restenosis of the index lesion, as assessed by quantitative coronary arteriography. Of 404 patients randomly assigned to study groups, 384 underwent angioplasty; 354 of the procedures were successful, and 321 patients underwent angiographic restudy at six months.

RESULTS

At base line, the patients in the lovastatin group (n = 203) and the placebo group (n = 201) were similar with respect to demographic clinical, angiographic, and laboratory characteristics. At base line the mean (+/- SD) degree of stenosis, expressed as a percentage of the diameter of the vessel, was 64 +/- 11 percent in the lovastatin group, as compared with 63 +/- 11 percent in the placebo group (P = 0.22). Despite a 42 percent reduction in the serum level of low-density lipoprotein cholesterol in the lovastatin group, after six months of treatment the amount of stenosis seen in the second angiogram was 46 +/- 20 percent in the placebo group, as compared with 44 +/- 21 percent in the lovastatin group (P = 0.50). Similarly, there were no significant differences in minimal luminal diameter or other measures of restenosis. A trend was noted toward more myocardial infarctions in the lovastatin group, as a result of acute vessel closure or restenosis at the site of angioplasty, but there were no other important differences between the two groups in the frequency of fatal or nonfatal events at six months.

CONCLUSIONS

Treatment with high-dose lovastatin initiated before coronary angioplasty does not prevent or delay the process of restenosis in the first six months after the procedure.

Do fish oils prevent restenosis after coronary angioplasty?

BACKGROUND

The omega-3 polyunsaturated fatty acids derived from fish oils have been shown to modulate many factors believed to affect the pathogenesis of atherosclerosis. Because certain features of restenosis following angioplasty mimic some of the early changes of atherogenesis, some researchers have suggested that fish oil might prevent restenosis following angioplasty. We report the effects of omega-3 fatty acids on the rate of restenosis following percutaneous intraluminal coronary angioplasty (PTCA).

METHODS AND RESULTS

From August 1989 through September 1992, 551 patients were randomized to start receiving a daily dietary supplement of ten 1.0-g capsules containing 80.6% ethyl esters of omega-3 fatty acids providing 4.1 g eicosapentaenoic acid (EPA) and 2.8 g docosahexaenoic acid (DHA) for 6 months or an equal amount of an ethyl ester of corn oil. Four hundred seventy subjects who were well matched for risk factors completed successful angioplasty of one or multiple lesions in native coronary vessels and constituted the study cohort, of whom 447 were evaluable at 6 months after PTCA. The criteria for restenosis were that the quantitative coronary angiography at 6 months show a > 30% increase in narrowing at the stenosis site or loss of at least half of the gain achieved at the time of PTCA and final restenosis with < 50% luminal diameter remaining. In 93% of the patients, the end point was determined by angiography and in all except 1% of these by quantitative coronary angiography. Compliance with the fish oil supplement was good as judged by incorporation of EPA and DHA in plasma and red blood cell phospholipids. The restenosis rate among analyzable patients was 46% for corn oil and 52% for fish oil (P = .37). The addition of 200 mg alpha-tocopherol for all subjects during the study had no effect on restenosis rates.

CONCLUSIONS

This was the largest of such trials to date, and a supplement of 8 g/d of omega-3 fatty acids failed to prevent the usual high rate of restenosis after PTCA. No adverse effects were attributable to this large daily supplement of omega-3 fatty acids.

Serum lipids and restenosis after successful percutaneous transluminal coronary angioplasty. Ichilov Magnesium Study Group

The effects of plasma lipids on the clinical and angiographic parameters of 134 patients, in whom coronary angioplasty was performed in 157 vessels, were prospectively examined. During a 6-month follow-up, restenosis was detected angiographically in 39 patients (29%; 45 vessels). None of the clinical, biochemical, or angiographic variables examined was predictive of stenosis and the tendency of a vessel to restenose was not patient-dependent but rather lesion-related. However, restenosis developed in 31 of 102 vessels (30%) in patients with high-density lipoprotein (HDL) cholesterol < or = 40 mg/dl, compared with restenosis in 10 of 55 vessels (19%) in patients with HDL cholesterol > 40 mg/dl (p = 0.092). No significant differences were observed when restenosis rates were compared in patients with total cholesterol levels > 250 mg/dl or < 250 mg/dl; no differences were seen in low-density lipoprotein (LDL) cholesterol levels when comparing patients with > 160 mg/dl and < 160 mg/dl. In 117 patients (132 vessels), complete serial blood specimens were obtained until the concluding angiography at 6 months. During follow-up, both groups (those with and without restenosis) had almost similar findings. Triglycerides decreased equally in both groups, and total cholesterol increased mildly in those who had restenosis; HDL and LDL cholesterol levels increased significantly in each group. No significant differences were observed with respect to extent of these changes between the groups. Thus, although lipid levels at the time of angioplasty and at 6 months follow-up were not found to predict the occurrence of restenosis, the association of low high-density lipoprotein levels and the tendency for restenosis should not be overlooked.

Fish oil and the prevention and regression of atherosclerosis

Epidemiological studies in the seventies have put forward that dietary rather than genetic factors are responsible for the lower incidence of ischemic heart disease in Greenland Inuit and have generated a large body of both in vitro and in vivo experimental studies, exploring the putative favorable effects of fish (oil) on atherogenesis and its risk factors. The first part of this report reviews the in vivo animal studies, concentrating on the hypercholesterolemic models and the arterialized vein graft model. In the hypercholesterolemic animal studies, the results are inconclusive as the studies reporting a protective effect are matched by the number of studies showing no effect or an adverse effect. The diversity in species, dose of fish oil, duration of study, type of vessel studied and type of fish oil preparation (content of n-3 fatty acids, unesterified n-3 fatty acids, ethylesters or triglycerides) could all contribute. Furthermore, the definitions and criteria used in the literature to evaluate atherogenesis are diverse and it appears that while one parameter is affected, another is not necessarily modified in the same direction, stressing the importance of extending the analysis of the effects on atherogenesis to more than one parameter. We also believe that it is time to reach a consensus as to which animal model mimics most closely a particular human situation. Only in appropriate models, investigating more than one atherosclerosis variable, can the effects of a putative anti-atherogenic drug or diet be verified. In the veno-arterial autograft model, mimicking the patient after coronary bypass grafting, dietary fish oil has been consistently effective in preventing accelerated graft intima proliferation. It could therefore be of interest to evaluate the effects of fish oil on graft patency in patients after coronary bypass surgery after a period of years. The results from studies on restenosis after percutaneous transluminal angioplasty are also reviewed and it is concluded that the two large scale trials, that are currently underway, might reliably answer the question whether fish oil is effective as a non-pharmacological adjuvants in the prevention of restenosis. Lastly, the studies on the effects of fish oil on the regression of experimental atherosclerosis are reviewed. In view of the small number of studies (i.e., four) investigating the effects of fish oil on the regression of atherosclerosis, it is premature to draw any conclusion, and therefore further experimental work is required.

Review of dietary intervention studies: effect on coronary events and on total mortality

The perfect randomised controlled dietary prevention trial of coronary heart disease has never been done. The best we can do is to look at all the trials together. Dietary trials should be separated from drug trials because they have different characteristics. Fourteen dietary trials which had disease or death as the end point are collected in this review for a meta-analysis. Three of the trials had two parts (male/female or low fat/increased fish), making a total of 17 trials. All were randomised trials, except the Finnish mental hospital trial which was a 12-year crossover in two hospitals. The trials were primary or secondary, diet only or multifactorial; numbers of subjects range from 52 to 57,460. For total deaths the ratio of intervention/control in all 17 trials is 0.94 (significantly less than 1.00) and for coronary events the pooled odds ratio is 0.87. But in the seven trials with most effective cholesterol lowering the odds ratios are 0.89 for all deaths and 0.70 for coronary events. There is thus no indication of excess all causes mortality in the dietary trials. Four recent secondary prevention trials had angiographic end points. There were a total of 275 subjects; trials were in Holland, USA, Germany and UK. In all trials plasma cholesterol was effectively lowered and coronary narrowing regressed a little, or progressed less in the diet group but significantly compared with controls. These angiographic trials strongly support the results of the major prevention trials. Lastly, a set of ten trials with fish oil after coronary angioplasty are reviewed. In some there appeared to be lower rates of restenosis, but not in all. The mechanism here is different from the major trials with plasma cholesterol-lowering diets for longer periods.

Perspectives on invasive cardiology: the 24th Louis F. Bishop Lecture

The fast growing and complex field of invasive cardiology offers a host of opportunities and challenges for the clinician. Scientific and technical advances ranging from molecular biology to microtechnology are changing how physicians make decisions concerning treatment of coronary artery disease, myocardial infarction, unstable angina and electrophysiologic dysfunction. The economic impact and ethical implications presented by these developments contribute to the difficulty of achieving optimal therapeutic solutions for individual patients.

Fish oils and their possible role in the treatment of cardiovascular diseases

The multifactorial origin of arteriosclerotic cardiovascular diseases is well recognized. It recently has been shown that n-3 fatty acids (FA), contained in fish oils, may correct some of the most important cardiovascular risk factors and may interfere with key steps in the formation of the atherosclerotic plaque. These findings have raised such interest that many reports have been published with somewhat conflicting results. In hypertensive patients, randomized controlled studies have confirmed that n-3 FA may reduce systolic blood pressure by 5 mmHg and diastolic by 4 mmHg. The decrease in pressure, which could be larger if dietary sodium restriction is added, is probably due to the shift of balance between vasoconstrictive and vasodilator eicosanoids toward vasodilatation. n-3 FA correct endogenous hypertriglyceridemia, but the effects on low-density lipoprotein and high-density lipoprotein cholesterol are less clear cut, since an increase in low-density lipoprotein and a decrease in high-density lipoprotein may be observed in selected patients. As far as the glucose metabolism in patients with diabetes mellitus is concerned, inhibition of the beta cell by n-3 FA has been reported. n-3 FA reduce platelet aggregation, blood viscosity, plasma levels of fibrinogen, PF4 and beta-thromboglobulin and increase capillary flow and red cell membrane fluidity, but their long-term effects on cardiovascular mortality are largely unknown. Medium-term studies, however, have shown a decreased risk of myocardial reinfarction and of restenosis after percutaneous transluminal coronary angioplasty with n-3 FA supplementation. Pure, highly concentrated triglycerides and ethyl esters of n-3 FA are available and will allow further investigations on the dose-response ratio in humans.

New antithrombotic strategies for resistant thrombotic processes

Life-threatening thrombo-occlusive events producing heart attacks and strokes develop in patients at sites of atherosclerotic arterial stenoses when plaques rupture, a process resistant to both aspirin and heparin. Resistant thrombotic complications are also troublesome during therapeutic thrombolytic or mechanical interventions for symptomatic atherosclerotic vascular disease, including angioplasty, various types of atherectomies, endarterectomy, endovascular stent deployment, or implanted small caliber vascular grafts. In this review therapeutic strategies for more effective management of these resistant, platelet-dependent, occlusive thrombi are discussed, including: a) inhibition of platelet recruitment by anti-GPIIb/IIIa monoclonal antibodies, naturally occurring peptides containing RGD sequences, or synthetic competitive analogs; b) direct inactivation of thrombin bound to thrombus by natural or synthetic antithrombin peptides; c) interruption of thrombin's production by natural or synthetic antagonists of Factor Xa or extrinsic and intrinsic coagulation pathways; and d) elimination of thrombogenicity at sites of vascular injury by immediately restoring confluent endothelium or prior therapy with dietary n-3 fatty acids. However, antagonists of both GPIIb/IIIa- and thrombin-dependent platelet recruitment produce equivalent inhibition of thrombus formation and platelet hemostatic function. Interestingly, hemostasis is spared by therapies that inhibit thrombin's production. Recommendations for development strategies are related to the relative hemostatic risks and antithrombotic benefits.

Southwestern internal medicine conference: restenosis: the Achilles heel of coronary angioplasty

Percutaneous transluminal coronary angioplasty has become the treatment of choice for many patients with symptomatic coronary artery disease. Increased experience with the procedure and improvements in equipment have resulted in high initial success rates; however, a significant number of patients develop restenosis. Insights into the pathophysiologic mechanisms of restenosis have led to the use of various pharmacologic agents and devices to prevent its occurrence. Although many have been successful in decreasing the incidence of restenosis in animal studies, none has yet proven successful in decreasing the incidence of restenosis in humans. Newer approaches and novel therapies are needed to prevent restenosis after percutaneous transluminal coronary angioplasty.

Restenosis after coronary angioplasty

Coronary angioplasty is used to treat coronary disease in many patients. Indications for angioplasty have expanded since it was first performed, mainly as a result of improvement in equipment and techniques. One problem with coronary angioplasty is the phenomenon of renarrowing of the treated coronary lesion, a process called restenosis. The events that constitute restenosis appear to be a universal response to the arterial wall injury of angioplasty. They are currently characterized as follows: platelet adhesion and aggregation on the damaged endothelium and within deep splits into the tunica media; release of platelet-derived growth factors; inflammation of the mechanically injured medial zone; transformation of smooth muscle cells of the tunica media after their activation by several of the growth-promoting substances; migration and proliferation of transformed smooth muscle cells, with secretion of copious amounts of extracellular matrix material; and, finally, termination of the growth process with regrowth of endothelium over the injured area. A decade of research work has helped identify clinical correlates of restenosis after coronary angioplasty procedures. This work is hindered by lack of a uniform angiographic definition of restenosis. In addition, much of the information has come from small studies, with incomplete follow-up and retrospective orientation. Nevertheless, some data are available. Patient-related correlates include male gender, unstable angina, diabetes, and continued smoking after angioplasty. Lesion-related correlates include multilesional and multivessel procedures, higher postangioplasty residual stenosis, proximal vessel location, location in the left anterior descending artery, location in a vein graft, long lesions, and total occlusions. The only consistent procedure-related correlate has been incorrect sizing of the angioplasty balloon to the treated artery. For the purposes of individual patient care, clinical correlates are not helpful. No group of variables has been found to be associated with complete freedom from restenosis, and no group is completely predictive of restenosis. All patients undergoing angioplasty procedures require some follow-up through subsequent months and years. Symptom status and the results of noninvasive studies have been investigated for purposes of follow-up. Symptoms are virtually useless by themselves for predicting restenosis or its absence. When symptom status is combined with exercise thallium 201 scintigraphy performed 4 to 6 months after an angioplasty procedure, the two factors are less than ideal but have a negative predictive value of more than 90%. This means that more than 90% of patients who have neither symptoms nor evidence of ischemia by thallium 201 scintigraphy will not have angiographic restenosis.(ABSTRACT TRUNCATED AT 400 WORDS)

Restenosis after coronary angioplasty

Coronary angioplasty is used to treat coronary atherosclerotic disease in many patients. One problem with coronary angioplasty is the phenomenon of restenosis. Restenosis appears to be a universal response to arterial wall injury. The biological events that underlie restenosis are characterized by: platelet adhesion and aggregation at sites of damaged endothelium, and within dissections into the medial layers, release of platelet derived growth-promoting substances, inflammation of the injured medial zone, transformation, migration, and proliferation of smooth muscle cells of the media following their activation by growth-promoting substances, secretion of copious amounts of extracellular matrix material, and finally, termination of the growth process following regrowth of endothelium over the damaged area. More than a decade of research work has helped identify clinical correlates of restenosis after coronary angioplasty. Patient-related correlates include male gender, unstable angina, diabetes, and continued smoking after angioplasty. Lesion-related correlates include multilesion and multivessel procedures, higher post-angioplasty residual stenosis, proximal vessel location, location in the left anterior descending coronary artery, location in a vein graft, long lesions, and total occlusions. However, for the purposes of individual patient care, clinical correlates are not particularly helpful. No group of variables has predicted complete freedom from restenosis, and conversely no group of variables has reliably indicated its presence. All patients undergoing angioplasty will require some form of follow-up evaluation. Symptom status by itself has not been found to be useful for predicting restenosis. However, when symptom status is combined with exercise thallium-201 scintigraphy, performed 4-6 months after angioplasty, it is less than ideal, but has a negative predictive value of over 90%. This means that over 90% of patients who are asymptomatic and have no evidence of ischemia by thallium-201 scintigraphy, will not have angiographic restenosis. Numerous clinical trials have been performed in order to reduce or prevent restenosis. Almost all have been disappointing, while a few have been encouraging. Studies of antiplatelet agents such as aspirin, dipyridamole (Boehringer Ingelheim Pharmaceuticals Inc., Ridgefield, CT, USA), and Ticlopidine (Syntex, Humgcao, Puerto Rico) have not shown efficacy, yet studies of an inhibitor of platelet-derived growth factor have been provocatively encouraging. No reduction in restenosis rates was found with the anticoagulants Coumadin (Du Pont Pharmaceuticals, Wilmington, DE, USA) and Heparin (Wyeth-Ayerst, Philadelphia, PA, USA). Fish oils (omega fatty acids) have been found in several clinical trials to provide modest, but encouraging, reductions in restenosis, but await further confirmation.(ABSTRACT TRUNCATED AT 400 WORDS)

N-3 fatty acids from fish oil. Effects on plasma lipoproteins and hypertriglyceridemic patients

In the experimental studies reported in this review, dietary n-3 fatty acids from fish and fish oil had profound hypolipidemic effects in normal subjects and in hypertriglyceridemic patients with combined hyperlipidemia (type II-b) and types IV and V hyperlipidemia. In these carefully controlled metabolic experiments, dramatic reductions occurred in plasma triglycerides and to a lesser extent in plasma total cholesterol. Reductions in VLDL, chylomicrons, remnants, LDL, apo B, and apo E were also noted. HDL changes varied from subject to subject. These plasma lipoprotein changes occurred in subjects with non-insulin-dependent diabetes mellitus as well, without deterioration of diabetic control. Similar results are reported in two other papers in this volume. Fish oil did not cause deterioration of diabetic control. Whereas the mechanism of the hypolipidemic action of the n-6 rich vegetable oils containing linoleic acid such as corn or safflower oil still remains obscure, the mechanism of the hypolipidemic action of the n-3 fatty acids in fish oil is well documented. The synthesis of triglyceride and VLDL in the liver is greatly reduced by n-3 fatty acids. At the same time, the turnover of VLDL in plasma is shortened. In another study, LDL production was decreased. Combined with other dietary manipulations, such as a reduction in saturated fat and dietary cholesterol, the use of n-3 fatty acids to treat hyperlipidemia, especially hypertriglyceridemia, appears to have a well-supported rationale. Fish oil combined with a low cholesterol, low saturated fat diet has been shown to produce complementary effects. Total plasma cholesterol and LDL cholesterol were lowered by the low cholesterol, low saturated fat diet, whereas plasma triglyceride and VLDL were decreased by the fish oil. In most situations, the use of fish oil supplements should be regarded as pharmacologic therapy, particularly effective in severe hypertriglyceridemic states (e.g., chylomicronemia). However, a lifelong diet rich in fish may be protective against atherosclerosis as well. Further studies are required to delineate exact doses and precise indications for the use of fish oil in different types of hyperlipidemias and to differentiate the effects, if any, of the two major n-3 fatty acids in fish oil, EPA and DHA. The hypolipidemic effects of n-3 fatty acids coupled with their known antithrombotic actions (secondary to changes in prostaglandin secretion, platelet function, inhibition of growth factors, and enhancement of endothelial-derived relaxation factor) appear to have an important potential role in the control of coronary heart disease and other atherosclerotic disorders. Moreover, fish oil may prevent the "chylomicronemia" syndrome of type V hyperlipidemia.

Dietary fish oil supplementation reduces myocardial infarct size in a canine model of ischemia and reperfusion

OBJECTIVES

This study was conducted to determine whether the long-term administration of fish oil attenuates myocardial necrosis in an occlusion-reperfusion model of myocardial ischemia.

BACKGROUND

Omega-3 fatty acids found in fish oil have various biologic properties that may modify myocardial injury caused by severe ischemia and reperfusion.

METHODS

Of 21 dogs fed an identical diet, 10 were given supplemental fish oil containing 0.06 g/kg per day of eicosapentaenoic acid for 6 weeks. Under anesthesia and open chest conditions, the left circumflex coronary artery was occluded for 90 min, followed by 6 h of reperfusion. Regional myocardial blood flow was measured with 15-microns spheres before and during occlusion and during reperfusion. The area at risk and infarct size were measured using standard staining techniques.

RESULTS

In the dogs receiving supplemental fish oil, the platelet cell membrane content of eicosapentaenoic acid increased from 0.9 +/- 0.56% to 7.1 +/- 4.0% (p < 0.001). Infarct size was 29 +/- 7% in the control group and 13 +/- 3% in the fish oil group (p < 0.05). There was no significant difference in the myocardial area at risk or rate-pressure product between the control and fish oil groups. There was no difference in regional myocardial blood flow between the groups at baseline study or during coronary occlusion and reperfusion.

CONCLUSIONS

Dietary fish oil supplementation significantly reduced myocardial infarct size in this model. The difference in infarct size did not appear to be related to dissimilarities in regional myocardial blood flow or determinants of oxygen consumption. Further investigation is needed to determine the nature of the protective mechanisms of omega-3 fatty acids on myocardial infarct size.

A prospective, randomized, and double-blind trial on the effect of fish oil on the incidence of restenosis following PTCA

Restenosis after successful coronary angioplasty (PTCA) occurs in 25-35% of all procedures. To date, most pharmacologic strategies have failed to reduce the restenosis rate significantly. However, recent studies have suggested a potential benefit of dietary supplementation with omega-3 fatty acids (fish oil) on restenosis following PTCA. The benefit of omega-3 polyunsaturated fatty acids on the incidence of coronary artery restenosis following elective PTCA was assessed in 212 consecutive patients (41 female, 171 male). Following a successful angioplasty, 204 patients received a dietary supplementation with either nine capsules containing fish oil (3.15 g omega-3 fatty acids) or nine placebo capsules containing olive oil. Treatment was started immediately after PTCA and maintained over 4 mon. Compliance was assessed by analysis of lipid fatty acids prior to angioplasty and at 4 mon follow-up. The angiographically determined incidence of restenosis (stenosis diameter > 50%) was 31.2% per lesion in patients receiving fish oil and 33.7% in patients receiving olive oil. Gross progression of coronary artery disease in vessels not subjected to angioplasty was 17% and 16%, respectively. In conclusion, low dose fish oil supplementation begun on the day of a successful coronary angioplasty failed to demonstrate any effect on coronary artery restenosis.

Pathophysiological mechanisms for restenosis following coronary angioplasty: possible preventive alternatives

Restenosis after successful percutaneous transluminal coronary angioplasty (PTCA) remains an unsolved medical problem. The search for the underlying pathophysiological mechanisms have identified intimal proliferation of smooth muscle cells (SMC) to be the prevailing cause of late restenosis, with endothelial cells (EC) and platelets being important participators in the process. According to the most accepted present theory, SMC would be stimulated to migrate and proliferate shortly after the angioplasty by the release of growth factors from injured EC and accumulated platelets. However, clinical trials of agents interfering with these mechanisms have not significantly diminished the rate of restenosis, which suggest both that our knowledge of the process is incomplete, and that new ways of administering the agents may be required.

Interruption of vascular thrombus formation and vascular lesion formation by dietary n-3 fatty acids in fish oil in nonhuman primates

BACKGROUND

Because of discrepant claims regarding the relative biological effects of n-3 fatty acids (n-3FAs), we have concurrently measured the effects of dietary n-3FAs on blood and vascular lipid composition, hemostatic function, blood thrombotic responses, vascular thrombus formation, and vascular lesion formation in baboons.

METHODS AND RESULTS

Dietary n-3FAs displaced n-6FAs in plasma, platelets, blood vessels, and corresponding urinary eicosanoid metabolites (p < 0.01 in all cases) within weeks after initiation of a semipurified diet containing 1 g/kg per day n-3FA-ethyl ester concentrate (composed of two thirds eicosapentanoic acid and one third docosahexanoic acid). Coincidentally, platelet hemostatic function became minimally impaired (template bleeding times prolonged from 4.3 +/- 0.5 minutes to 7.6 +/- 1.3 minutes, p = 0.039); concentrations of collagen producing half-maximal platelet aggregation increased (from 6.4 +/- 2.1 to 8.5 +/- 2.5 micrograms/mL, p = 0.045); and tissue factor expression by endotoxin-stimulated blood monocytes fell (from 6.5 +/- 1.2 to 1.7 +/- 0.14 mU/10(6) cells, p < 0.005). Dietary n-3FAs decreased deposition of platelets onto thrombogenic segments of Dacron vascular graft incorporated into chronic exteriorized femoral arteriovenous (AV) shunts, a thrombotic process resistant to the effects of both aspirin and heparin (111In-labeled platelet deposition decreased from 14.1 +/- 1.4 x 10(9) platelets/5-cm segment at 40-60 minutes with occlusion to 7.5 +/- 0.8 x 10(9) platelets/5-cm segment without occlusion; p < 0.001). Platelet deposition onto segments of endarterectomized homologous normal aorta in the AV shunts of n-3FA-treated animals was similarly reduced (from 4.4 +/- 0.9 to 1.8 +/- 0.4 x 10(9) platelets; p < 0.01). Dietary n-3FAs interrupted vascular thrombus formation at sites of surgical carotid endarterectomy (platelet deposition, 1.5 +/- 0.4 versus 4.4 +/- 1.0 x 10(9) platelets in untreated controls; p < 0.001). Moreover, endarterectomized aortic segments (EASs) from n-3FA-treated donors exhibited little capacity to induce thrombus formation when tested in the AV shunts of control recipient animals (0.24 +/- 0.10 versus 4.4 +/- 0.90 x 10(9) platelets). However, in the converse crossover experiments, EASs from control animals actively accumulated platelets when studied in the AV shunts of n-3FA-treated animals (1.8 +/- 0.4 x 10(9) platelets; p < 0.01 versus n-3FA-treated EASs in shunts of normal animals). Dietary n-3FAs also abolished vascular lesion formation at sites of carotid endarterectomy 6 weeks after surgery (cross-sectional area of neointima 0.048 +/- 0.031 mm2 compared with 0.428 +/- 0.104 mm2 in control arteries; p = 0.010).

CONCLUSIONS

In nonhuman primates, dietary n-3FAs in high doses eliminate both vascular thrombus formation and vascular lesion formation after mechanical vascular injury while largely sparing hemostatic function and modestly reducing blood thrombotic responses. These effects are attributed to selective n-3FA-dependent alterations in cellular membrane functions.

Use of fish oil to prevent coronary angioplasty restenosis

OBJECTIVE

To review the literature investigating the use of fish oil in preventing restenosis postangioplasty (RPA).

DATA SOURCES

An Index Medicus and bibliographic search of the English-language literature pertaining to the use of fish oil in preventing RPA. The key terms used were fish oil, angioplasty, and eicosapentaenoic acid.

STUDY SELECTION AND DATA EXTRACTION

The results of all trials, including abstracts, that were obtained are reviewed and critiqued.

DATA SYNTHESIS

Restenosis of a coronary vessel at the site of angioplasty occurs 30-40 percent of the time. Because fish oil has been theorized to prevent atherosclerosis and because atherosclerotic-like processes are theorized to be involved in RPA restenosis, fish oil has been studied to determine whether it can prevent RPA. Results of such trials have been mixed. Some have observed a reduction in the number of patients with angiographic or clinical evidence of restenosis. Two trials have failed to observe such an effect. Reasons for the differences are unknown. Possible explanations include differences in study design, endpoint parameters, definition of restenosis, and dosing methods of the fish oil. Bleeding was not of significant concern in any of the trials, even when fish oil was combined with antiplatelet therapy.

CONCLUSIONS

Fish oil may be considered for use in patients to prevent RPA. It probably should be continued for only six months following the procedure. Current data suggest that at least 3 g/d of eicosapentaenoic acid and 1 g/d of docosahexaenoic acid should be used. If possible, therapy should be started as soon as it is known that angioplasty will be performed or at least as soon as possible following the procedure. Many patients may not be able to tolerate fish oil because of its gastrointestinal effects.