Objective: To assess the risk of adverse cardiovascular events in women who discontinue hormone replacement therapy after myocardial infarction compared with those who continue.
Design: Nationwide register based cohort study.
Setting: All hospitals in Denmark.
Population: All 3322 women aged 40 years or over who survived 30 days after a myocardial infarction and were prescribed hormone replacement therapy at the time of myocardial infarction in the period 1997 to 2008.
Main outcome measures: Reinfarction, cardiovascular mortality, and all cause mortality 30 to 360 days after discharge.:
Results: A total of 282 (8.5%) women had a reinfarction, 218 (6.6%) died of cardiovascular causes, and 357 (10.7%) died of any cause during follow-up. Women who discontinued overall hormone replacement therapy in the first year after myocardial infarction did not have a significantly different risk of reinfarction (hazard ratio 0.90, 95% confidence interval 0.68 to 1.19), cardiovascular mortality (1.21, 0.90 to 1.62), or all cause mortality (1.22, 0.97 to 1.53) than women who continued use. However, discontinuation of vaginal oestrogen was associated with a lower risk of reinfarction (hazard ratio 0.54, 0.34 to 0.86).
Conclusion: No certain conclusions can be drawn regarding increased or decreased risk of adverse cardiovascular events with continuing hormone replacement therapy after myocardial infarction. The results rule out neither a modest benefit nor a worrisome increase in risk. These figures may be valuable when a possible cardiovascular risk of hormone replacement therapy needs to be balanced with menopausal symptoms for the individual patient.