The American Heart Association has issued revised guidelines on hormone replacement therapy (HRT) for postmenopausal women.
The new guidelines reverse previous recommendations and advise against the use of hormone replacement therapy for cardiovascular protection alone in postmenopausal women (Circulation 2001;104:499-503).
The revised recommendations were issued because of conflicting evidence about combined oestrogen and progestogen (known as progestin in the United States) therapy and its effects on the heart. Traditionally, hormone replacement therapy was believed to be good for the heart, and in recent years it has been prescribed not only to ward off menopausal symptoms, but also in the hope that it would reduce the risk of heart attack and stroke.
Epidemiological evidence supported this stance as heart attacks are rare in premenopausal women. Also, oestrogen replacement tends to improve lipid profiles because there is a shift towards increased production of high density lipoproteins and a reduction in low density lipoproteins, which are associated with atherosclerotic plaque formation.
Although conventionally thought to be beneficial, hormone replacement also changes coagulation proteins, increases thromboembolic events, and increases the risk of breast and endometrial cancers. Moreover, new data show that hormone replacement has either a negligible or a negative effect on the heart.
In arriving at its new guidelines, the American Heart Association relied on two main studies, the heart and oestrogen-progestin replacement study and the oestrogen replacement and atherosclerosis trial.
The heart and oestrogen-progestin replacement study was the first large scale, randomised, clinical outcome trial designed to test whether oestrogen-progestogen therapy was beneficial in secondary prevention of non-fatal infarcts and coronary heart disease. The study found a 52% increase in adverse cardiovascular events (from 28.0 to 42.5 per 1000 person years) in the first year of therapy in patients with a history of heart disease who underwent hormone replacement.
After 4.1 years of follow up the study found no significant difference in non-fatal heart attacks and coronary deaths between the hormone replacement and placebo arms.
Results from the oestrogen replacement and atherosclerosis trial supported the findings of the first study. This second study used angiographic imaging to document whether hormone replacement slowed the progression of arteriosclerosis in patients with a history of coronary stenosis. The study found no significant change when compared with placebo.
As a result of these studies, the American Heart Association has warned doctors against prescribing oestrogen-progestogen replacement for secondary prevention of heart disease. Moreover, it has recommended considering discontinuation of replacement therapy and instituting prophylaxis for venous thrombosis in women who develop an acute coronary event while taking oestrogen-progestogen replacement.
The association also stated that there are insufficient data to support a role for hormone replacement therapy for primary prevention of heart disease, and recommendation for primary prevention awaits the results of ongoing clinical trials.
In conclusion it stated that "initiation and continuation of hormone replacement therapy should be based on established non-coronary benefits and risks, possible coronary benefits and risks, and patient preference."