Cardiac MRI improves risk stratification for STEMI patients

For revascularized ST-segment elevation myocardial infarction (STEMI) patients, early post-infarction cardiac MRI parameters offer long-term predictive value that is superior to that offered by traditional outcome predictors, a large, long-term European study has found.

The paper was published online Aug. 16 in JACC: Cardiovascular Imaging.

“Early post infarction cardiac MR-based microvascular obstruction (MVO) is a strong independent prognosticator in reperfused STEMI patients at long-term follow-up,” wrote the authors, led by Rolf Symons with the University Hospital Gasthuisberg in Leuven, Belgium.  “Remarkably, MVO extent > 2.6 percent of left ventricle was the strongest independent predictor of death and heart failure hospitalization, overriding the prognostic performance of traditional outcome predictors and leading to better long-term risk stratification,” they stated.

The most recent guidelines for STEMI patients issued by the American Heart Association/American College of Cardiology and the European Society of Cardiology recommend that clinicians factor in left ventricular (LV) ejection fraction quantification as part of their decision-making and risk stratification processes, according to the researchers. However, LV ejection fraction is heavily influenced by post-infarction stunning and compensatory hyperkinesis of noninfarcted myocardium, diminishing its usefulness as a prognostic marker.

For STEMI patients, cardiac MRI, on the other hand, provides quantitative multiparametric characterization of the infracted myocardium, as well as a full assessment of LV function and morphology. The authors of the JACC study maintain, though, that previous studies of cardiac MRI in STEMI patients had serious limitations, including single-center designs, small sample sizes, brief follow-up and the adoption of soft clinical endpoints.

The JACC: Cardiovascular Imaging study addressed these limitations. The cohort comprised 810 revascularized STEMI patients who were enrolled between May 2003 and August 2015. The patients, who came from six tertiary referral hospitals throughout Europe, were all older than 18 years and had been successfully treated by percutaneous coronary intervention within 12 hours of the onset of symptoms.

Follow-up began at the time of the CMR, and patients were followed for a minimum of one year and up to the closing date of August 2016. The median duration of follow-up was 5.5 years (range from 1.0 to 13.1 years), for a total of 4,305 years of patient follow-up.