Why are women with ST-elevation myocardial infarction treated differently to men?

STEMI and coronary artery disease are major but underappreciated killers of Australian women

This issue of the Journal includes confronting data about inequities in the treatment and outcomes for men and women with ST-elevation myocardial infarction (STEMI).1 Khan and colleagues report that the 6-month mortality for women presenting with STEMI is twice that of men, a difference that persists after statistical correction for age and comorbid conditions. The article relates worrying evidence of a disparity in the delivery of evidence-based treatment, raising many important questions: What barriers are preventing women from presenting for treatment earlier? Why are there delays in providing women with recognised life-saving treatments? Why are women as a group treated less intensively than men despite having higher Global Registry of Acute Coronary Events (GRACE) risk scores? What biological differences require distinct therapeutic approaches and dedicated clinical trials?

Women were found to present later after symptom onset than men (median, 16 minutes: 120 v 104 min). Although the causes of this delay are not clear, efforts to improve public awareness of the incidence and potential differences in symptoms of heart attacks in women, such as those of the National Heart Foundation,2 need to be amplified, accompanied by clear messages about the importance of urgently seeking medical attention.

The speed of STEMI diagnosis in women must improve. Health care workers need to recognise that women with STEMI often present with non-specific or poorly localised chest pain, shortness of breath, or constitutional symptoms. Standardised treatment policies and “code STEMI” protocols need to be promoted and implemented more widely, as they have been shown to reduce sex differences in care.3

The report by Khan and colleagues also clearly shows that female STEMI patients, despite being at higher risk of mortality, are receiving guideline-directed invasive and reperfusion therapies less often than men.4 Potential explanations for this paradox include a failure to recognise markers of risk and concerns by physicians about the impact of other factors, including age, on the safety profile of revascularisation therapies. We need to ask whether clinicians’ fear of complications is contributing to unacceptably high mortality rates among women with myocardial infarction. There is no evidence that primary percutaneous coronary intervention or thrombolysis are less effective in women; on the contrary, their benefit is greatest in patients at greatest risk of death.5

In addition to these factors, the distinct pathophysiology of coronary artery disease and post-infarct ventricular remodelling in women probably contribute to worse clinical outcomes.6,7 The study by Khan and his co-authors confirmed that women with STEMI have non-obstructive coronary artery disease more frequently than men (12.1% v 3.7%); the absence of underlying coronary obstructions suggests that women presenting with STEMI may have had a reduced rate of ischaemic preconditioning and collateral development, worsening their prognosis.7 Clinical trials for treatment of myocardial infarction with non-obstructive coronary arteries (MINOCA) are needed to determine the efficacy of anti-platelet, lipid-lowering, and angiotensin-converting enzyme inhibitor therapies for these patients. Novel therapies may be needed for this challenging and poorly understood cause of myocardial infarction.

It has previously been reported that women are at increased risk of death after STEMI,8 and Khan and colleagues provide definitive evidence from a large, contemporary group of patients with STEMI that this is a problem in Australia. Action needs to be taken on three major fronts: community education to improve the timeliness of presentation by women with heart attack; improved adherence to guidelines in the treatment of women with STEMI; and increased attention to differences in the pathophysiology of women in the design of clinical trials. Together, these approaches will contribute to improving outcomes for women, for whom STEMI and coronary artery disease are major but underappreciated killers.