Combined OCT, Cardiac MRI Unravels Root Cause in Most MINOCA

Patrice Wendling

November 14, 2020

Optical CT (OCT) plus cardiac MRI (CMR) provides a more specific diagnosis in the majority of women presenting with myocardial infarction with nonobstructive coronary arteries (MINOCA).

The multimodal imaging strategy identified the underlying cause of MINOCA in 85% of women in the HARP-MINOCA study. Overall, 64% of women had a true MI and 21% had an alternate nonischemic diagnosis, most commonly myocarditis.

"OCTCMR findings correlated well with OCT culprit lesions, demonstrating that nonobstructive culprit lesions frequently cause MINOCA," said study author Harmony Reynolds, MD, director of New York University Langone's Sarah Ross Soter Center for Women's Cardiovascular Research.

Dr Harmony Reynolds

The results were presented at the virtual American Heart Association (AHA) Scientific Sessions 2020 and published simultaneously in Circulation.

MINOCA occurs in up to 15% of patients with MI and is defined as MI meeting the universal definition but with less than 50% stenosis in all major epicardial arteries on angiography and no specific alternate diagnosis to explain the presentation.

It is three times more common in women than in men and also disproportionately affects Black, Hispanic, Maori, and Pacific persons. MINOCA has several causes, leading to uncertainty in diagnostic testing and treatment.

"Different doctors tell patients different messages about MINOCA and may incorrectly say the event wasn't a heart attack," Reynolds said in an earlier press briefing. "I had a patient who was told 'your arteries are open,' and they gave her Xanax."

As part of the Women's Heart Attack Research Program (HARP), researchers enrolled 301 women with a clinical diagnosis of MI, of whom 170 were diagnosed with MINOCA during angiography and underwent OCT at that time, followed by CMR within 1 week of the acute presentation.

All images were interpreted by an independent core laboratory blinded to results of the other tests and clinical information. The final cohort included 145 women with interpretable OCT images.

Their median age was 60 years, 49.7% were white non-Hispanic, and 97% presented with a provisional diagnosis of non–ST-segment MI. Their median peak troponin level was 0.94 ng/mL.

OCT identified a definite or probable culprit lesion in 46% of women, most commonly atherosclerosis or thrombosis. On multivariable analysis, having a culprit lesion was associated with older age, abnormal angiography findings at the site, and diabetes, but not peak troponin level or severity of angiographic stenosis.

CMR available in 116 women showed evidence of infarction or regional injury in 69%. Multivariate predictors of an abnormal CMR were higher peak troponin and diastolic blood pressure but not an OCT culprit lesion or angiographic stenosis severity.

When the OCT and CMR results were combined, a cause of MINOCA was identified in 84.5% of women. Three-fourths of the causes were ischemic (64% MI) and one-quarter were nonischemic (15% myocarditis, 3% Takotsubo syndrome, and 3% nonischemic cardiomyopathy). In the remaining 15%, no cause of MINOCA was identified.

To emphasize the effect multimodal imaging can have on treatment, Reynolds highlighted a 44-year-old woman with no risk factors for coronary artery disease who had chest pain in the context of heavy menstrual bleeding, a low hemoglobin level, and peak troponin level of 3.25 ng/mL.

Unexpectedly, imaging revealed a left anterior descending (LAD) plaque rupture in a thin-cap fibroatheroma, causing a small transmural infarction at the terminus of the LAD.

"Without this diagnosis, it's unlikely she would have received antiplatelet therapy or statins and might have been given a diagnosis of supply/demand mismatch, when the real diagnosis was MI," Reynolds observed.

"Finally we can say this is not just crazy women. There is really something going on," panelist Roxana Mehran, MD, Icahn School of Medicine at Mount Sinai in New York City, remarked. "You have now told us this is most likely atherosclerosis for pretty much 85% of the cases. So make the diagnosis and, of course, make sure you treat these patients accordingly for risk factor modification, really thinking about a ruptured plaque."

Combining OCT and MRI may result in a more specific diagnosis and better treatment but also raises costs and logistical considerations.

"Implementation challenges are that not every form of testing is available in every medical center," Reynolds told | Medscape Cardiology. "Many centers have cardiac MRI," whereas "OCT is not currently available at most medical centers where heart attack patients are treated but is available at specialized centers."

Asked during the session about the use of CT angiography, Reynolds said, "For me, CT is helpful when I'm not sure if there's any plaque because the angiogram looked really normal and there was no opportunity to do intracoronary imaging. And sometimes that will help me, in particular, if a patient doesn't want to take a statin."

Invited discussant, Martha Gulati, MD, president-elect of the American Society for Preventive Cardiology, pointed out that the European Society of Cardiology MINOCA guidelines recommend OCT and CMR, whereas the 2019 AHA statement on MINOCA, which she coauthored, also recommends OCT and CMR, but almost as one or the other.

"We already said that you should do cardiac MR to try to make a diagnosis, but I think the combination of the two needs to be emphasized when we next draft these guidelines. It really will help," Gulati told | Medscape Cardiology.

"But using OCT, particularly, needs to be in the setting of the MI. I don't think you want to do a procedure again," she said. "So we really need it to become more widely available because at the time of an MI, you won't necessarily know that you're not going to find an obstructive lesion."

Gulati pointed out several unanswered questions, including whether the diagnosis was missed in some patients, because OCT of all three vessels was available in only 59%, and how the use of high-sensitivity troponin, which was left up to the individual institution, might affect the usefulness of OCT and CMR.

It's also unknown whether the mechanism is different for ST-segment elevation MI, as the trial included very few cases, although MINOCA often occurs in this setting. Future OCT/CMR studies will also need to enroll men to determine potential sex differences, if any.

Commenting on the study for | Medscape Cardiology, B. Hadley Wilson, MD, Sanger Heart & Vascular Institute in Charlotte, North Carolina, said, "There would need to be further justification of this invasive interventional procedure to be sure that the benefit outweighed the risk of putting a wire and an OCT catheter down patients without any significant angiographic blockage and to assure interventional cardiologists of its value here."

He pointed out that noninvasive CMR appears helpful in the diagnosis of nearly three-quarters of these patients and perhaps could be done first to direct which of those with an ischemic cause might benefit from invasive OCT at catheterization. This seems most pertinent in patients with a high suspicion of coronary artery disease or recurrent MINOCA.

"Overall, we need to consider the expense, logistics, and small risk of these combined modalities, particularly in everyday practice, before making recommendations," Wilson said. "Additionally, since OCT is much less available than intravascular ultrasound, it would require a challenging marketplace paradigm shift to implement this multimodality imaging strategy regionally and locally in the U.S., including the added costs. However, further study to direct the more judicious use of either CMR and/or combined with OCT is warranted in these patients."

The study was funded by the AHA through a grant from the Go Red for Women Strategically Focused Research Network. Reynolds reported in-kind donations from Abbott Vascular and Siemens related to the study and nonfinancial support from BioTelemetry outside the study. Gulati and Wilson reported having no relevant disclosures.

American Heart Association (AHA) 2020 Scientific Sessions. Presented November 14, 2020.

Circulation. Published online November 14, 2020. Abstract

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