Janet Wei, MD
Myocardial infarction with nonobstructive coronary arteries (MINOCA) accounts for up to 10% of patients presenting with myocardial infarction and predominantly affects young women. The Barbra Streisand Women’s Heart Center at the Smidt Heart Institute is currently leading a multicenter clinical trial to assess whether standard therapy used for obstructive coronary artery disease is effective for women with MINOCA. Cardiologist Janet Wei, MD,co-director of the Stress Echocardiography Laboratory and associate medical director of the Biomedical Imaging Research Institute at Cedars-Sinai, explains why more research into MINOCA’s underlying causes is needed to improve treatment options.
1. Diagnosis Can Be Elusive
MINOCA patients present with nonobstructive coronary arteries on angiography (< 50% stenosis) and no clinically overt specific cause for the acute presentation. MINOCA can result from a number of conditions, but in a majority of MINOCA patients the underlying mechanisms remain unknown. There are some shared patient risk profiles with myocardial infarction—high blood pressure, high cholesterol, diabetes, smoking—but they are less frequent in MINOCA patients than in patients who have had AMI with obstructive CAD.
There are other underlying causes of MINOCA that are more common in women than men. These include coronary artery spasms and spontaneous coronary artery dissection. These are the most common causes of myocardial infarction in pregnant and postpartum women.
2. Ethnic Disparities May Play a Role
Compared to patients with myocardial infarction due to obstructive coronary artery disease, MINOCA patients are more likely to be female and younger, and they’re also more likely to be Black or Latino. Prior studies have shown that Black or Latino patients—in particular, young Black women—have a lower prevalence of obstructive coronary artery disease than white/non-Latino patients when they present with chest pain or are being evaluated for heart attack. It’s unclear if this difference may be due to disparities in healthcare referral patterns for testing or racial/ethnic differences.
3. Treatments Should Be Tailored
Currently, treatment protocols for MINOCA are often the same as for MI: anti-platelet therapy, statins, ACE-inhibitors/angiotensin receptor blockers (ACE-I/ARB) and beta-blockers. The SWEDEHEART registry demonstrated that statins, ACE-I/ARB and possibly beta-blockers were associated with fewer major adverse cardiac events in long-term follow-up of patients with MINOCA (Lindahl B, et al. 2017). However, these therapies should be tailored in patients with MINOCA, particularly in those without atherosclerosis. For example, it is still unknown whether this treatment strategy should be the same for those who had MINOCA due to coronary vasospasm, embolism or spontaneous coronary artery dissection. A stratified medical approach is being studied in MINOCA (https://clinicaltrials.gov/ct2/show/NCT05198791).
4. More Research Is Needed
The Barbra Streisand Women’s Heart Center participated in the Heart Attack Research Program, supported by the American Heart Association, in which advanced imaging techniques were tested to help better understand MINOCA in women. The study found that a combination of techniques that included optical coherence tomography (OCT) at the time of initial coronary angiography and cardiac magnetic resonance imaging (MRI) within one week of acute presentation allowed the team to diagnose the cause of MINOCA in over 80% of cases (Reynolds HR, et al. 2021). For example, OCT was able to detect plaque rupture, thrombus, intraplaque cavity, layered plaque, spontaneous coronary artery dissection and suspected vasospasm. Cardiac MRI with T2-weighted and late gadolinium-enhanced images helped to distinguish ischemic from nonischemic causes of elevated troponin (such as myocarditis, Takotsubo cardiomyopathy and nonischemic cardiomyopathy). Another study recently showed that earlier imaging with cardiac MRI (median three days after acute presentation) increased diagnostic utility compared to imaging at a median of twelve days (Sorensson P, et al., 2021).
5. What the WARRIOR Trial Is Revealing (and Why It Matters)
The Women’s Ischemia Trial to Reduce Events In Non-Obstructive CAD (WARRIOR) is a multicenter, prospective, randomized, blinded outcome evaluation of a pragmatic strategy of intense medical therapy versus standard of care in 4,422 symptomatic women with suspected INOCA (including recent MINOCA) in approximately 70 U.S. sites. The study utilizes web-based data capture, electronic consents, single IRB and centralized pharmacy distribution of strategy medications directly to patients’ homes to reduce site and patient burden. A biorepository will collect blood samples to assess potential mechanisms. The results will provide evidence necessary to inform future guidelines regarding how best to treat this growing population of patients and ultimately improve the patients’ cardiac health and quality of life and reduce healthcare costs.
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Lindahl B, et al. Circulation. 2017 Apr 18;135(16):1481-1489.
Reynolds HR, et al. Circulation. 2021 Feb 16;143(7):624-640.
Sorensson P, et al. JACC: Cardiovasc Imaging. 2021;14(9):1774-1783.