Background:
Myocardial infarction with non-obstructive coronary arteries (MINOCA) occurs in 6-15% of MI and disproportionately affects women. Scientific statements recommend multi-modality imaging in MINOCA to define the underlying cause. We performed coronary optical coherence tomography (OCT) and cardiac magnetic resonance imaging (CMR) to assess mechanisms of MINOCA.
Methods:
In this prospective, multicenter, international, observational study, we enrolled women with a clinical diagnosis of MI. If invasive coronary angiography revealed <50% stenosis in all major arteries, multi-vessel OCT was performed, followed by CMR (cine imaging, late gadolinium enhancement, and T2-weighted imaging and/or T1 mapping). Angiography, OCT, and CMR were evaluated at blinded, independent core laboratories. Culprit lesions identified by OCT were classified as definite or possible. The CMR core laboratory identified ischemia-related and non-ischemic myocardial injury. Imaging results were combined to determine the mechanism of MINOCA, when possible.
Results:
Among 301 women enrolled at 16 sites, 170 were diagnosed with MINOCA, of whom 145 had adequate OCT image quality for analysis; 116 of these underwent CMR. A definite or possible culprit lesion was identified by OCT in 46.2% (67/145) of participants, most commonly plaque rupture, intra-plaque cavity or layered plaque. CMR was abnormal in 74.1% (86/116) of participants. An ischemic pattern of CMR abnormalities (infarction or myocardial edema in a coronary territory) was present in 53.4% of participants undergoing CMR (62/116). A non-ischemic pattern of CMR abnormalities (myocarditis, takotsubo syndrome or non-ischemic cardiomyopathy) was present in 20.7% (24/116). A cause of MINOCA was identified in 84.5% of the women with multi-modality imaging (98/116), higher than with OCT alone (p<0.001) or CMR alone (p=0.001). An ischemic etiology was identified in 63.8% of women with MINOCA (74/116), a non-ischemic etiology was identified in 20.7% (24/116), and no mechanism was identified in 15.5% (18/116).
Conclusions:
Multi-modality imaging with coronary OCT and CMR identified potential mechanisms in 84.5% of women with a diagnosis of MINOCA, three-quarters of which were ischemic and one-quarter of which were non-ischemic, alternate diagnoses to MI. Identification of the etiology of MINOCA is feasible and has the potential to guide medical therapy for secondary prevention.
Clinical Trial Registration:
URL: https://clinicaltrials.gov Unique Identifier: NCT02905357
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Beta-Blockers [BB] have been used extensively in the last 40 years after acute myocardial infarction [AMI] as part of therapy and in secondary prevention. The evidence for “routine” therapy with beta-blocker use post AMI rests largely on results of trials conducted over 25 years ago. However, there remains no clear recommendation regarding the appropriate duration of treatment with BBs in post AMI patients with normal left ventricular ejection fraction [LVEF] who are not experiencing angina, or who require BB for hypertension or dysrhythmia. Based on the latest ACC/AHA guidelines, BBs are recommended for early use in the setting of AMI, except in patients who are at low risk and then indefinitely as secondary prevention after AMI. This recommendation was downgraded to class IIa in low risk patients and the updated 2007 ACC/AHA guidelines suggest that the rationale for BB for secondary prevention is from limited data derived from extrapolations of chronic angina and heart failure trials. In this review, we examine the key trials that have shaped the current guidelines and recommendations. In addition, we attempt to answer the question of the duration of BB use in patients with preserved LVEF after acute MI, as well as which subgroups of patients benefits most from post AMI use of beta blockers.
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