Hormone therapy might be protective in postmenopausal women during a first myocardial infarction (MI), but could increase the risk — and severity — of a second, results from an observational Finnish study suggest.
“Our data show that hormone therapy has some protective effect on vascular health, probably due to the vasodilatory effect of estradiol on blood vessels,” said Pauliina Tuomikoski, MD, from Helsinki University, who presented the results at the North American Menopause Society 2015 Annual Meeting.
“However, women should probably not continue hormone therapy use after the first MI, since it seems to increases the risk of a second MI, which may be fatal,” she said.
The 7258 women in the study cohort experienced their first MI from 1995 to 2009, and were entered in FINAMI, a population-based register of acute coronary events in Finland.
At the time of their MI, 625 of the women were using hormone therapy and 6633 were not.
In an age-adjusted analysis, women on hormone therapy were less likely than women on nonhormone therapy to die before reaching the hospital (22% vs 25.8%; odds ratio [OR], 0.77; P = .023). They also had a lower fatality rate in the month after MI (18.5% vs 24.7%; OR, 0.68; P = .007) and in the year after MI (42.5% vs 51.7%; OR, 0.62; P < .001).
“MI is quite fatal, but maybe a little bit less fatal in women who use hormone therapy,” said Dr Tuomikoski.
Duration of hormone therapy had an effect on the fatality rate in the 28 days after the MI. For the 415 women who had been on hormone therapy for less than 5 years, the fatality rate was 38.5% (OR, 0.83); for the 210 who had been on hormone therapy for at least 5 years, it was 29.8% (OR, 0.54); and for women who had never been on hormone therapy, it was 43.4% (P < .001).
However, age at the initiation of hormone therapy had little effect on MI fatality risk.
Table 1. MI Fatality by Age Group and Hormone Use
|Age at Initiation of Hormone Use||Odds Ratio|
|All hormone users|
|Hormone users at the time of MI|
There was also an association between fatality and the use of hormone therapy after MI.
In fact, “the odds ratio for getting a second MI with continued hormone therapy use was 1.6, and there was a threefold risk for that second MI to be fatal with continued use,” Dr Tuomikoski reported.
Table 2. Use of Hormone Therapy After MI
|Hormone Use After MI||n||Rate of Recurrent MI, %||1-Year Fatality Rate, %|
“This might be due to the fact that the women who get the first MI likely have other unstable plaques that are prone to rupture, and estrogen is known to destabilize plaques,” senior author Tomi Mikkola, MD, PhD, also from Helsinki University, said.
“These registry data should be interpreted with caution,” said Mary Norine Walsh, MD, medical director of the heart failure and cardiac transplantation programs at the St. Vincent Heart Center of Indiana in Indianapolis, who is vice president of the American College of Cardiology.
“For decades, observational studies led to the belief that hormone therapy protected women from coronary heart disease. Randomized controlled trials later showed that postmenopausal women with coronary heart disease were at increased risk if they were on estrogen,” she said. In this study, the researchers looked at the association between prescription data and data in an MI registry, but important information is lacking, she pointed out.
“Prospective data on the use of hormone therapy initiated at the time of menopause in large populations of women without coronary heart disease will help answer the question about the cardiovascular effect of hormone therapy.”
Source: North American Menopause Society (NAMS) 2015 Annual Meeting: Abstract S-13. Presented October 2, 2015.