MINOCA: Looking for the Myocardial Infarction Culprit

MINOCA: Looking for the Myocardial Infarction Culprit Posted By:
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A 45-year-old female presents to the ER with chest pain, ST elevation on EKG, and a troponin of 2.5 ng/mL. She is rushed to the catheterization lab for a coronary angiogram, but there is no obstructive disease observed. What should be the next step?

February was American Heart Month, but it is always an opportune time to review myocardial infarction (MI) with non-obstructive coronary arteries (MINOCA). MINOCA is a syndrome accounting for 5% to 10% of all MI and one-third of patients will have ST elevation. Patients with MINOCA are more likely to be younger females or ethnic minorities compared with those who have MI related to coronary artery disease (MI-CAD). The 2019 Statement by the American Heart Association provides a framework for the diagnosis of MINOCA. Alternative conditions like sepsis, pulmonary embolism, and cardiac contusion should be excluded using clinical context. Non-MI cardiac conditions such as takotsubo syndrome, myocarditis, or spontaneous coronary artery dissection (SCAD) may clinically mimic MINOCA. Initially thought to be relatively benign compared to MI-CAD, a meta-analysis of MINOCA studies showed a pooled in-hospital mortality rate of 0.9%, and a pooled 12-month mortality rate of 4.7%.

Thankfully arteries are made bigger than we need them to be, though blockages still occur. When a patient presents with chest pain and a coronary angiogram shows a >70% blockage, it is easy to determine the cause and how to fix it. However, if the angiogram shows no significant stenosis (≤50%) but clinically mimics an MI, there are a few other explanations to explore.

Cardiac MRI (CMRI) can help investigate the cause of MINOCA. In pooled analyses of CMRI publications in patients with MINOCA, CMRI showed myocarditis in 33%, MI in 24%, takotsubo cardiomyopathy in 18%, and normal myocardial findings in 26%. This imaging can help determine if there are extracardiac or reversible conditions, such as myocarditis and takotsubo. CMRI can also help determine if further testing is warranted—such as further review of the angiogram for a dissection flap. If the cause was a spontaneous coronary dissection vs a small MI in a distal vessel seen on a CMRI, the indication for dual antiplatelet therapy would be very different.

The SWEDEHEART registry followed more than 9000 patients with MINOCA for 4 years. When analyzed for associations between treatments and long-term cardiovascular events, it was found that statin or angiotensin-converting enzyme inhibitors/angiotensin receptor blockers were associated with significantly reduced cardiovascular events. Beta blockers showed a trend toward long-term benefit, while the impact of dual antiplatelet therapy was neutral. Future research on MINOCA should include randomized controlled trials on secondary prevention treatment options.

For our original patient, we ordered a CMRI which showed myocarditis; 2 weeks later, it resolved. This test helped clarify our plan not to use dual antiplatelet therapy or a statin.

In summary, when MI is suspected, keep looking for the culprit—even if the first evaluation is unrevealing for an obstruction—as that will help determine the optimal care.

References
  • Eckenback C, et al. MINOCA from A to Z. www.acc.org/latest-in-cardiology/articles/2022/01/05/17/41/minoca-from-a-to-z. Accessed March 1, 2022.
  • Lindahl B, et al. Medical therapy for secondary prevention and long-term outcome in patients with myocardial infarction with nonobstructive coronary artery disease. Circulation. 2017;135:1481.
  • Pasupathy S, et al. Systematic review of patients presenting with suspected myocardial infarction and nonobstructive coronary arteries. Circulation. 2015;131:861.
  • Smilowitz NR, et al. Mortality of myocardial infarction by sex, age, and obstructive coronary artery disease status in the ACTION Registry-GWTG (Acute Coronary Treatment and Intervention Outcomes Network Registry-Get With the Guidelines). Circ Cardiovasc Qual Outcomes. 2017;10:e003443.
  • Sorensson P, et al. Early comprehensive cardiovascular magnetic resonance imaging in patients with myocardial infarction with nonobstructive coronary arteries. JACC Cardiovasc Imaging. 2021;14:1774.
  • Tamis-Holland J, et al. Contemporary diagnosis and management of patients with myocardial infarction in the absence of obstructive coronary artery disease: A scientific statement from the American Heart Association. Circulation. 2019;139:e891.

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Filed under: Cardiometabolic

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