Cardiac MRI Improves Culprit Lesion Identification in NSTEMI

USA: Identification of the infarct-related artery (IRA) by coronary angiography can be challenging in patients with non–ST-segment–elevation myocardial infarction (MI). A new study published in the journal Circulation: Cardiovascular Interventions, has found that delayed-enhancement cardiac magnetic resonance (DE-CMR) may lead to a new IRA diagnosis or elucidate nonischemic pathogenesis in patients with non–ST-segment–elevation MI (heart attack).

Determining the infarct-related artery (IRA) in non–ST-segment–elevation MI can be challenging. DE-CMR can accurately identify small MIs. John F. Heitner, NewYork-Presbyterian Brooklyn Methodist Hospital, Brooklyn, NY, and colleagues conducted the study to determine whether DE-CMR improves the ability to identify the IRA in patients with non–ST-segment–elevation MI.

The study showed that the infarct-related-artery (IRA) could not be identified by invasive coronary angiography in 37% of 114 patients with NSTEMI. DE-CMR, however, identified the IRA in 60% of these patients and led to a new nonischemic diagnosis in a further 19%.

The researchers enrolled 114 patients presenting with their first MI in this 3-center, prospective study. The interventional cardiologist was blinded to the DE-CMR results. Later, coronary angiography and DE-CMR images were reviewed independently and blindly for identification of the IRA. The pattern of DE-CMR hyperenhancement was also used to determine whether there was nonischemic pathogenesis for myocardial necrosis.

Key findings of the study include:

• In 72 patients whose IRA was picked up by angiography, DE-CMR found hyperenhancement consistent with MI in a different territory in 14%.


• Another 10 patients (12.5%) were deemed to have a nonischemic diagnosis, including myocarditis in seven, Takotsubo cardiomyopathy in one, and amyloidosis in one.


• For the entire population, DE-CMR significantly increased IRA identification vs coronary angiography (72% vs 63%), driven primarily by those without significant coronary artery disease (CAD; 54% vs 22%).


• DE-CMR led to a new IRA diagnosis in 35 patients, a nonischemic diagnosis in 17, or either in 52 patients, although the 95% confidence interval was wide, at 37% to 55%.


• Of 55 patients undergoing revascularization, 27% had revascularization solely to nonculprit coronary artery territories as determined by DE-CMR.

"The main findings are that identification of the IRA by coronary angiography is challenging, and DE-CMR may lead to a new diagnosis or elucidate a new nonischemic etiology in nearly half the cohort," wrote the authors.

"Identification of the IRA by coronary angiography can be challenging in patients with non–ST-segment–elevation MI. In nearly half, DE-CMR may lead to a new IRA diagnosis or elucidate nonischemic pathogenesis. Revascularization solely of coronary arteries that are believed to be nonculprit arteries by DE-CMR is not uncommon," they concluded.

For detailed study log on to https://doi.org/10.1161/CIRCINTERVENTIONS.118.007305