Estrogen replacement therapy and outcome of coronary balloon angioplasty in postmenopausal women

Phytoestrogen derivatives differentially inhibit arterial neointimal proliferation in a mouse model

Neointimal proliferation is a key element in atherosclerotic plaque formation and in arterial restenosis following angioplasty. Estrogen-like compounds, including naturally occurring plant phytoestrogens, are known to alter the extent of neointimal proliferation. This study investigates the anti-atherogenic/restenotic effect of several synthetic metabolites of isoflavone phytoestrogens (dihydrodaidzein, tetrahydrodaidzein and dehydroequol) (Novogen, Sydney, Australia). Acute neointimal proliferation was induced in the iliac artery of cholesterol-fed mice, by mechanically damaging the endothelium. Phytoestrogens were administered orally for 4 weeks and the damaged arteries harvested. Intimal area, as a percentage of the iliac artery wall area, was measured. Dihydrodaidzein significantly halved the intimal response (intima approximately 25% of wall area; p < 0.01) compared with placebo diet-fed mice (intima approximately 50% of wall area), while tetrahydrodaidzein and dehydroequol showed no inhibitory effects. Immunohistochemistry demonstrated that alpha-actin-positive vascular smooth muscle cells were the major cell type in the proliferating neointima. A single layer of endothelium covered the thickened intima by 4 weeks. Thus, a specific phytoestrogen isoflavone compound (dihydrodaidzein) can selectively inhibit neointimal proliferation, either by inhibition of vascular smooth muscle cell migration and proliferation, and/or by enhancing endothelial proliferation and function, and inhibition of endothelial apoptosis.

Continuation of hormone replacement therapy during acute myocardial infarction after the women's health initiative study. Is it the time for change?

Hormone replacement therapy (HRT) was given for many years in order to relieve menopausal symptoms and was used for as long as symptom control was necessary. The Heart and Estrogen/Progestin Replacement Study (HERS) and Women's Health Initiative (WHI) studies showed that HRT should not be given for primary or secondary prevention of coronary heart disease (CHD). However, what about those patients during acute myocardial infarction who are already taking HRT? Is the 'don't stop don't start' rule still true? A 58-year-old white female, on HRT was admitted with acute myocardial infarction (MI). We tried to answer the above questions in light of the new information:Based on current evidence available from HERS and WHI trials, it is not advisable to initiate HRT in women with established CHD for the sole purpose of preventing first or recurring coronary events. A statement by the American Heart Association recommends that the decision to continue or stop HRT in women with CV disease should be based on established benefits and risks, taking patients preference into account. The WHI study did not change this policy in the acute phase. In most cases, we believe HRT should be continued for some period (our decision for 3 months long was arbitrary), and discontinued gradually. We believe that this should be the policy until we have a double-blind placebo-control data to revise.

HRT and heart disease: problems and prospects

The divergent findings of hormone replacement therapy (HRT) from observational and randomized clinical studies are summarized and reasons for the different results are postulated. Chronic use of HRT since menopause has no harmful effects on CHD event rate, while the initiation of therapy after a recent cardiovascular event causes an early increase in recurrent CHD events. Once endothelial dysfunction and atherosclerotic disease has developed, the starting of HRT promotes plaque instability, vascular inflammation and prothrombotic effects. The timing of HRT use since menopause is therefore crucial in the effectiveness and safety of HRT on the vascular system.

“Rise and fall” of hormone therapy in postmenopausal women with cardiovascular disease

Whereas observational data for postmenopausal women using hormone therapy (HT) have shown a protective effect against cardiovascular disease, prospective, randomized trials have demonstrated a harmful effect on the vascular system. This study describes the effects of HT on lipids, hemostatic parameters, inflammation, and the vascular wall. Reasons for the different results of observational and experimental studies of HT are postulated. The timing of hormonal supplementation seems crucial. Used chronically, HT has no harmful effects; however, first-time use of HT after a recent cardiovascular event results in an early increase in adverse cardiovascular events. In most observational studies, women started HT for postmenopausal symptoms, whereas in experimental studies, women started HT 10 to 20 years or longer after menopause. Cumulative evidence supports the hypothesis that HT has more effect in maintaining vascular health than in alleviating endothelial dysfunction. HT has not proven beneficial in the long term in women at risk of a cardiovascular event. The interval between menopause and the start of HT plays a crucial role in the effectiveness of HT in the vascular system.

The Osteoporosis Prevention and Arterial effects of tiboLone (OPAL) study: design and baseline characteristics

The Osteoporosis Prevention and Arterial effects of tiboLone (OPAL) trial is a three-arm, randomized, placebo-controlled, double-blind study to determine the effect of tibolone 2.5 mg (Org OD 14) and continuous combined conjugated equine estrogens plus medroxyprogesterone acetate (0.625 mg/2.5 mg respectively) on progression of intima-media thickness of the carotid arteries and bone mineral density of the lumbar vertebrae and proximal femur in postmenopausal women. A total of 866 healthy postmenopausal women were recruited in six U.S. centers and five European centers. Duplicate carotid ultrasound examinations of the common carotid artery, the carotid bifurcation, and the internal carotid artery were performed at baseline. Single measurements of bone mineral density of the lumbar vertebrae and proximal femur were obtained at baseline. After randomization, ultrasound examinations were repeated every 6 months for 36 months following baseline, with a duplicate examination at the end of the study. Bone mineral density was measured every 12 months throughout the trial. The primary outcome is change in mean common carotid intima-media thickness (CIMT), defined as the average of the intima-media thickness measurements performed circumferentially at predefined angles for the near and far wall of 10-mm segments of the right and left distal common carotid arteries. Unique new features of the OPAL study are the specifically developed OPAL ultrasound protocol, yielding highly reproducible CIMT measurements, and the use of two experienced core laboratories for CIMT readings (one in the United States and one in Europe) with one common quality assurance and control program. The OPAL study is a large, placebo-controlled trial evaluating the effects of tibolone, as well as one of the first large randomized studies to determine the effects of continuous combined estrogen-progestin therapy on carotid atherosclerosis in healthy postmenopausal women. The OPAL study results are expected to complement other studies on atherosclerosis progression in healthy postmenopausal women.

Cholesterol-fed ovariectomized monkeys are good animal models for human atherosclerosis of postmenopausal women

Although it is well known that the incidence of atherosclerosis is markedly increased in postmenopausal women, antiatherosclerotic effects of estrogen replacement therapies are not clear. One of the reasons for this is due to the lack of appropriate animal models for atherosclerosis of postmenopausal women. Therefore, we attempted to develop an animal model for atherosclerosis of postmenopausal women and examined the antiatherosclerotic effects of estrogen replacement therapy. Adult ovariectomized Japanese monkeys were fed 2% cholesterol diet alone (C-group) or in combination with conjugated estrogen (CE-group) for 30 months. The serum estradiol-17beta levels of the CE-group were varied between 10 and 204.5 ng/dl during treatment. In the C-group, the serum total cholesterol levels were increased from 110 to 270 mg/dl, and atheroma was first observed after 3-months treatment with angioscopy. In the CE-group, the levels of the serum total cholesterol during treatment were 30% lower than those of the C-group, and the aortic lesions were first observed after 12-months treatment with angioscopy. The aortic intimal thickness of the CE-group was 58% of the C-group. This finding showed good agreement with the angioscopic observation. The aortic lesions were of a fibromuscular type in both groups. In conclusion, a cholesterol-fed ovariectomized monkey is an appropriate animal model for atherosclerosis of postmenopausal women. Furthermore, angiofiberscopic and histopathological observations suggested that estrogen replacement therapy was valid for atherosclerosis of postmenopausal women.

Estrogen-eluting, phosphorylcholine-coated stent implantation is associated with reduced neointimal formation but no delay in vascular repair in a porcine coronary model

Estrogen can inhibit intimal proliferation and accelerate endothelial regeneration after angioplasty. This suggests that estrogen may prevent in-stent restenosis. Unlike other therapies to prevent restenosis, estrogen may also not delay endothelial regrowth, thereby avoiding the risk of late stent thrombosis. The purpose of this work was to determine the effect of a 17beta-estradiol-eluting stent on neointimal formation in a porcine model. Each artery of six pigs was randomized to either a control, low-dose, or high-dose 17beta-estradiol-eluting stent. All animals were sacrificed at 30 days for histopathological analysis. There was a 40% reduction in intimal area in the high-dose stents compared with control stents (2.54 +/- 1.0 vs. 4.13 +/- 1.1 mm(2), for high dose vs. control, respectively; P < 0.05). There was complete endothelial regeneration at 30 days and similar inflammatory response to stenting on histopathology in all the stent groups. This is the first study to show that 17beta-estradiol-eluting stents are associated with reduced neointimal formation without affecting endothelial regeneration in the pig model of in-stent restenosis. Estrogen-coated stents may have a potential benefit in the prevention and treatment of in-stent restenosis.

Hormone therapy and in-hospital survival after myocardial infarction in postmenopausal women

BACKGROUND

Although postmenopausal hormone therapy (HRT) commonly is used in hope of preventing coronary heart disease, the effect of HRT on case fatality of myocardial infarction has never been studied. We evaluated HRT as a predictor of survival after MI in postmenopausal women.

METHODS AND RESULTS

The present study was performed with 114 724 women of age >/=55 years with confirmed myocardial infarction who presented between April 1998 and January 2000 to 1 of 1674 hospitals participating in the National Registry of Myocardial Infarction-3. Presenting characteristics, treatment, and clinical outcome data were obtained by chart review. At time of hospitalization, 7353 (6.4%) women reported current use of HRT, defined as use of estrogen, progestin, or estrogen/progestin for reasons other than contraception. Unadjusted mortality was 7.4% in users of HRT and 16.2% in nonusers (odds ratio 0.41, 95% confidence interval 0.36 to 0.43). After adjustments were made for prior medical history, clinical characteristics, treatments received in-hospital, and likelihood of receiving HRT, HRT remained associated with an improved rate of survival (odds ratio 0.65, 95% confidence interval 0.59 to 0.72). Significant association of HRT with decreased mortality after myocardial infarction was observed in all age strata.

CONCLUSIONS

Postmenopausal HRT appears to be associated with reduced mortality after myocardial infarction. This finding could be caused by therapeutic effect of HRT, selection and adherence bias, or some combination of both.

Postmenopausal oestrogen replacement therapy and atherosclerosis: can current compounds provide cardiovascular protection?

The natural oestrogen, 17 beta-oestradiol, has been implicated in protection from atherosclerosis, a chronic systemic vascular disease with an inflammatory component accounting for the majority of morbidity and mortality in Western countries. Despite the protective effects of 17 beta-oestradiol in premenopausal women and experimental evidence demonstrating inhibitory effects of oestrogen on atherosclerosis progression, it is currently unclear whether hormone replacement therapy can affect cardiovascular morbidity and mortality in postmenopausal women. The recent advances in understanding the mechanisms of oestrogen action demonstrated roles for different oestrogen receptors and oestrogen metabolites in the pathogenesis of vascular injury and endothelial cell dysfunction. However, their respective role in the process of atherogenesis remains yet to be elucidated. Moreover, the availability of novel drugs with tissue- and/or receptor-specific actions will help to understand the role of oestrogen in cardiovascular diseases. Several ongoing large-scale clinical trials using opposed or unopposed replacement therapy with natural or synthetic oestrogens, or selective oestrogen receptor modulators (SERMs) will resolve the question whether the drugs currently available have therapeutic potential to interfere with the progression of atherosclerosis and its complications.

HRT to prevent cardiovascular disease. What studies show, how to advise patients

How should you advise postmenopausal patients who are considering estrogen therapy? Do the potential cardiovascular benefits outweigh the risks? Does hormone therapy improve the cardiovascular risk profile in women with established coronary artery disease? In this article, Drs Wood and Cox help clarify the current clinical data for and against hormone replacement therapy for prevention of cardiovascular disease. In addition, they discuss current treatment recommendations and future directions in hormone therapy.

Long-term (three years) effect of estrogen replacement therapy on major adverse cardiac events in postmenopausal women after intracoronary stenting

This study examined whether estrogen replacement therapy (ERT) in postmenopausal women impacts intermediate and long-term outcome after successful coronary stenting. Our findings offer evidence that ERT significantly reduces target lesion revascularization after intracoronary stenting in postmenopausal patients who are on ERT before the intervention.

Heart disease in women. Gender-specific statistics and prevention strategies for a population at risk

For decades, coronary artery disease (CAD) was thought to be primarily a disease of middle-aged men, in whom most research was conducted. But CAD afflicts a diverse patient population, and a major subset of those patients--women--present special diagnostic and therapeutic challenges for the primary care physician. In this article, Dr Rosenfeld provides an overview of CAD in women and discusses its causes and risk factors, prevention strategies, and gender-specific characteristics. She also examines the effect of gender-biased research on the views of both patients and physicians.

Effect of 6-wk estrogen withdrawal or replacement on myocardial ischemic tolerance in rats

Menopausal status is a risk factor for coronary artery disease death, but the mechanism underlying this association is uncertain. To test whether estrogen ameliorates the effects of acute myocardial ischemia in ways likely to translate into a mortality difference, we compared the response to brief (6-min) and prolonged (45-min) coronary occlusion in vivo in five groups (each n = 16) of rats: ovariectomized females; ovariectomized females after 6 wk 17beta-estradiol replacement; male rats supplemented with estradiol for 6 wk; normal males; and normal females. Coronary occlusion produced a uniform ischemic risk area averaging 53 +/- 3% of left ventricular volume. After a brief occlusion, reperfusion ventricular tachycardia/fibrillation occurred with >85% frequency in all groups. During a prolonged occlusion, ischemic ventricular tachycardia occurred in 100% and sustained tachycardia requiring cardioversion in >75% of rats in all groups. Myocardial infarct size averaged 52 +/- 4% of the ischemic risk area and was similarly unaffected by gender or estrogen status. We conclude that neither short-term estrogen withdrawal, replacement, nor supplementation significantly affects the potentially lethal outcomes from acute coronary occlusion in this species.

CME Paper: Hormone Replacement Therapy for Prevention or Treatment of Atherosclerosis in Postmenopausal Women: Promises, Controversies, and Clinical Trials

Cardiovascular disease is the leading cause of death among men and women in the U.S. and other developed societies. However, myocardial infarction and stroke are uncommon in women until their sixth decade and beyond. Clinicians have long suspected that the delay of a decade or more in cardiovascular disease expression in women relative to men is due to the protective effects of estrogen prior to menopause. Reports from population based observational studies of the favorable effects of hormone replacement therapy on cardiovascular morbidity and mortality have led to enthusiasm for widespread use of estrogen by postmenopausal women for the prevention of cardiovascular disease. In support of the antiatherogenic potential of estrogen are studies in postmenopausal women showing favorable effects on lipoprotein levels, fibrinolysis, and vascular function. However, a secondary prevention trial in postmenopausal women with coronary artery disease showed no cardiovascular benefit of hormone replacement therapy. Ongoing clinical trials and options to conventional hormone replacement therapy for cardiovascular protection will be discussed in this review. (c)2000 by CVRR, Inc.

Hormone replacement therapy and cardiovascular disease

A large amount of research continues to be conducted on the mechanisms of hormone replacement therapy (HRT) effects, and the first of the large clinical trials published its results during the past year. In addition to the well known effects on LDL-cholesterol, HDL-cholesterol, and triglycerides, recent studies confirmed that estrogen with or without a progestin lowers lipoprotein (a) concentrations in women (but not in men). In men, estrogen appears to have a similar effect on other lipids and lipoproteins and on plasminogen activator inhibitor-1 as in women. A comparison of estrogen with simvastatin indicated that simvastatin is better at lowering LDL-cholesterol while estrogen is better at raising HDL-cholesterol; when given in combination the additional effects were modest. Estrogen and simvastatin had similar beneficial effects on endothelial function. The estrogen effect on endothelial function may be blocked by medroxyprogesterone, but the data are inconsistent. These studies of intermediate outcomes were put in perspective by the results of a landmark secondary prevention trial of coronary heart disease (CHD). This randomized placebo-controlled trial (Heart and Estrogen/Progestin Replacement Study) of conjugated equine estrogens plus medroxyprogesterone failed to show the anticipated reduction in CHD, and at the same time the threefold increase in venous thromboembolism confirmed that HRT is procoagulant. Therefore, it is still not known whether HRT is a viable option for the prevention of CHD. The preliminary data on selective estrogen receptor modulators are not overly promising, but a definitive trial to test whether raloxifene will reduce CHD is ongoing.

Postmenopausal hormone use for cardioprotection: what we know and what we must learn

Coronary heart disease is a highly prevalent and lethal illness for women, particularly in their menopausal years, a fact that fostered interest in hormone use for cardioprotection. Despite the compelling evidence of cardiovascular benefit of estrogen therapy and estrogen and progestin therapy in observational studies of postmenopausal women, and multiple biologically plausible mechanisms for estrogen benefit, precise clinical outcome information from prospective randomized controlled trials is lacking. The only such trial reported, the Heart and Estrogen/Progestin Replacement Study, not only failed to demonstrate cardioprotection, but showed an early adverse outcome in women with documented coronary heart disease who received daily conjugated equine estrogen and medroxy-progesterone acetate. Several large randomized clinical trials of hormone and selective estrogen receptor moderator therapy for primary and secondary prevention are currently underway.

Arthur C. Corcoran Memorial Lecture. Hormones and vasoprotection

There is a strong link between menopause and increased cardiovascular disease incidence in women, and observational studies suggest that postmenopausal hormone replacement therapy reduces cardiovascular disease risk by about half. Observational studies suffer from important limitations, however, and the only published prospective controlled trial of the effects of hormone replacement therapy on cardiovascular outcomes, the Heart Estrogen-Progestin Replacement Study (HERS), showed no net benefit of continuous estrogen plus synthetic progestin treatment in women with established coronary disease. Fundamental mechanistic studies of the cellular and molecular events by which hormones protect (or fail to protect) blood vessels from damage are needed to define the role of postmenopausal hormone replacement therapy in cardiovascular disease prevention. Most studies suggest that estrogen inhibits the neointimal response to acute injury in normal blood vessels, but this vasoprotective effect was not seen in vessels with preexisting atherosclerosis. Studies from our laboratory in the rat carotid injury model have shown that estrogen inhibits neointima formation via effects on all 3 layers of the vascular wall, including inhibition of medial smooth muscle cell migration and proliferation, stimulation of regrowth of endothelium, and inhibition of adventitial cell migration into neointima. Our laboratory is currently using transduced (lacZ) syngeneic fibroblasts as 'reporter' cells to delineate the factors that stimulate migration of adventitial cells into neointima after vascular injury and their modulation by estrogen and the other sex hormones. These fundamental studies will establish more rational strategies for therapeutic intervention in vascular diseases, including the basis for future gene therapy.