Female Cardiac Advantage Essentially Lost After MI

Patrice Wendling

October 07, 2020

Women are known to lag 5 to 10 years behind men in experiencing coronary heart disease (CHD), but new research suggests the gap narrows substantially following a myocardial infarction (MI).

"Women lose a considerable portion, but not all, of their coronary and survival advantage (ie, the lower event rates) after suffering a MI," study author Sanne Peters, PhD, George Institute for Global Health, Imperial College London, England, told theheart.org | Medscape Cardiology in an email.

Previous studies of sex differences in event rates after a coronary event have produced mixed results and were primarily focused on mortality following MI. Importantly, the studies also lacked a control group without a history of CHD and, thus, were unable to provide a reference point for the disparity in event rates, she explained.

Using the MarketScan and Medicare databases, however, Peters and colleagues matched 339,890 US adults hospitalized for an MI between January 2015 and December 2016 with 1,359,560 US adults without a history of CHD.

Over a median 1.3 years follow-up, there were 12,518 MIs in the non-CHD group and 27,115 recurrent MIs in the MI group.

The age-standardized rate of MI per 1000 person-years was 4.0 in women and 6.1 in men without a history of CHD, compared with 57.6 in women and 62.7 in men with a prior MI.

After multivariate adjustment, the women-to-men hazard ratio for MI was 0.64 (95% CI, 0.62 - 0.67) in the non-CHD group and 0.94 (95% CI, 0.92 - 0.96) in the prior MI group, the authors reported October 5 in the Journal of the American College of Cardiology.

Additional results show the multivariate adjusted women-to-men hazard ratios for three other cardiovascular outcomes follow a similar pattern in the non-CHD and prior MI groups:

  • CHD events: 0.53 (95% CI, 0.51 - 0.54) and 0.87 (95% CI, 0.85 - 0.89)

  • Heart failure hospitalization: 0.93 (95% CI, 0.90 - 0.96) and 1.02 (95% CI, 1.00 - 1.04)

  • All-cause mortality: 0.72 (95% CI, 0.71 - 0.73) and 0.90 (95% CI, 0.89 - 0.92).

"By including a control group of individuals without CHD, we demonstrated that the magnitude of the sex difference in cardiac event rates and survival is considerably smaller among those with prior MI than among those without a history of CHD," Peters said.

Of note, the sex differences were consistent across age and race/ethnicity groups for all events, except for heart failure hospitalizations, where the adjusted hazard ratio for women vs men age 80 years or older was 0.95 for those without a history of CHD (95% CI, 0.91 - 0.98) and 0.99 (95% CI, 0.96 - 1.02) for participants with a previous MI.

Peters said it's not clear why the female advantage is attenuated post-MI but that one explanation is that women are less likely than men to receive guideline-recommended treatments and dosages or to adhere to prescribed therapies after MI hospitalization, which could put them at a higher risk of subsequent events and worse outcomes than men.

"Sex differences in pathophysiology of CHD and its complications may also explain, to some extent, why the rates of recurrent events are considerably more similar between the sexes than incident event rates," she said. Compared with men, women have a higher incidence of MI with nonobstructive coronary artery disease and of heart failure with preserved ejection fraction, and evidence-based treatment options are more limited for both conditions.

"After people read this, I think the important thing to recognize is we need to push — as much as we can, with what meds we have, and what data we have — secondary prevention in these women," Laxmi Mehta, MD, director of preventive cardiology and women's cardiovascular health at The Ohio State University, Columbus, said in an interview.

The lack of a female advantage post-MI should also elicit a "really meaningful conversation with our patients on shared decision making of why they need to be on medications, remembering on our part to prescribe the medications, remembering to prescribe cardiac rehab, and also reminding our community we do need more data and need to investigate this further," she said.

In an accompanying editorial, Nanette Wenger, MD, Emory University School of Medicine in Atlanta, Georgia, also points out that nonobstructive coronary disease is more common in women and, "yet, guideline-based therapies are those validated for obstructive coronary disease in a predominantly male population but, nonetheless, are applied for nonobstructive coronary disease."

She advocates for aggressive evaluation and treatment for women with chest pain symptoms as well as early identification of women at risk for CHD, specifically those with metabolic syndrome, preeclampsia, hypertensive disorders of pregnancy, chronic inflammatory conditions, and high-risk race/ethnicity.

"Next, when coronary angiography is undertaken, particularly in younger women, an assiduous search for spontaneous coronary artery dissection and its appropriate management, as well as prompt and evidence-based interventions and medical therapies for an acute coronary event," Wenger writes. "However, basic to improving outcomes for women is the elucidation of the optimal noninvasive techniques to identify microvascular disease, which could then enable delineation of appropriate preventive and therapeutic approaches."

Peters is supported by a UK Medical Research Council Skills Development Fellowship. Mehta and Wenger disclosed no relevant financial relationships.

J Am Coll Cardiol. 2020;76:1751-60, 1761-62. Article, Editorial

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