Update to Chapter 39: Evaluation and Management of Non-ST -Segment Elevation Myocardial Infarction

Study Summary

The HARP-MINOCA trial evaluated the underlying cause of myocardial infarction with non-obstructive coronary arteries (MINOCA) using coronary optical coherence tomography (OCT) and cardiac magnetic resonance (CMR) in women. This prospective, multicenter, observational trial included 301 women with clinical diagnosis of myocardial infarction, of whom 170 had <50% coronary stenosis (MINOCA) on catheterization (see accompanying Hurst’s Central Illustration). This group was further evaluated by multivessel OCT (N = 145) and CMR (N = 116). A definite or possible culprit lesion on OCT (plaque rupture, intra-plaque cavity, or layered plaque) was present in 46.2%. One patient had spontaneous coronary artery dissection (0.7%). CMR was abnormal in 74.1%, with an ischemic pattern (infarction or edema in a coronary territory) in 53.4% and a nonischemic pattern (myocarditis, takotsubo, or non-ischemic cardiomyopathy) in 20.7%. In 116 women undergoing both tests, the etiology of MINOCA could be identified in 85% (more than with each modality alone), with the majority being ischemic (64%). This study investigators propose atherothrombosis with possible contribution of coronary spasm as a common etiology of MINOCA in women and highlight the role of imaging for guiding secondary prevention.

Commentary

Study Strengths: This well-designed prospective, international, observational study was undertaken in 16 sites and multivessel OCT and CMR were performed in 170 women with MINOCA. Both modalities were reviewed by dedicated core labs. The close correspondence between the location of culprit lesions on OCT and the affected myocardial territory on CMR provided strong evidence that non-obstructive atherosclerosis frequently causes MINOCA in women.

Study Limitations: A relatively small sample size and recruitment of disproportionally high NSTEMI cases (97%) are among limiting factors. The complete CMR and OCT protocol could not be implemented in all patients, which may have caused underdetection of culprit lesions or myocardial injury. On CMR, myocardial edema in a coronary territory was considered evidence of ischemic injury although regional myocarditis cannot be excluded in such cases. Additionally, a control group was not included due to the potential risk of multivessel OCT. Short duration of follow-up and small sample size limited assessment of the prognostic significance of findings.

Next Steps/Clinical Perspective: Both OCT and CMR provided useful diagnostic information independently and, particularly, in combination. The imaging findings indicated that non-obstructive atherothrombosis is the common etiology of MINOCA in women. The next steps should include study of a larger sample size of men and women for a longer period of time. As high-resolution LGE imaging may be more sensitive, it should be considered as part of the CMR protocol. Ultimately, the goal should be to determine if guiding secondary prevention on the basis of imaging findings improves outcomes, although this will require large sample sizes.

Trial Reference