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Cardiac magnetic resonance imaging may allow physicians to discern which patients are at highest risk for complications following myocardial infarction, according to US researchers.

The technique allows for differentiation between viable and nonviable myocardial tissue to evaluate infarct size.

The study group looked at CMR images from 122 patients who had had an ST-elevation myocardial infarction (STEMI) followed by percutaneous coronary intervention.

The findings showed a correlation between the size of the acute infarct and the initial end-systolic and end-diastolic volume indices and ejection fraction.

Over two years of follow-up, the researchers reported one death, one recurrent MI and 14 admissions with heart failure. The acute infarct size was significantly greater in all these patients, and was the strongest predictor of major cardiac events after multivariate analysis.

Using a cut-off infarct size of 18.5 per cent gave a sensitivity of 88 per cent and a negative predictive value of 96 per cent for adverse clinical events.

The authors concluded: "The negative predictive value [of infarct size] for both predicting which patients following STEMI will not develop [major cardiac events] or adverse LV remodelling were both high at over 90 per cent."

They added: "This high negative predictive value would suggest that quantifying the amount of infarcted myocardium can be a good negative screening test in patients. Therefore, CMR can prospectively discern which patients warrant close monitoring."

[1] Infarct size by contrast enhanced cardiac magnetic resonance is a stronger predictor of outcomes than left ventricular ejection fraction or end-systolic volume index: prospective cohort study

Heart 2008;94:730-736