Reproducibility of chronic and acute infarct size measurement by delayed enhancement-magnetic resonance imaging.

Objectives: The aim of this study was to evaluate the reproducibility of acute and chronic infarct size (IS) by delayed enhancement (DE) magnetic resonance imaging (MRI).

Background: Infarct size measurements can be used as surrogate end point to reduce the sample size in studies comparing different reperfusion strategies in myocardial infarction (MI). Delayed enhancement MRI is a rather new technique, and so far infarct IS reproducibility has not been established appropriately.

Methods: In 21 patients (10 acute MI and 11 chronic MI), IS was assessed repeatedly on consecutive days by DE-MRI. Reproducibility, interobserver, and intraobserver variabilities were assessed and compared by the Bland-Altman method.

Results: Acute and chronic IS were 17.1 +/- 19.6% (range 5.1% to 69.8%) of LV mass (%LV) and 16.9 +/- 9.9 %LV (range 2.0% to 36.0%), respectively. Infarct size difference (bias) between scan I and scan II was -0.5 %LV, and limits of agreement were +/-2.4 %LV. Mean bias (-0.7 %LV) and limits of agreement (+/-3.2%) were slightly higher for acute in comparison with chronic MI with -0.4 +/- 1.3 %LV. Intraobserver and interobserver variability was low with a mean bias of 0.3 %LV (limits of agreement +/- 1.7 %LV) and -0.7 %LV (limits of agreement +/- 2.2 %LV), respectively.

Conclusions: Infarct size measurement by DE-MRI is an excellent tool for IS assessment, owing to its excellent repeatability in chronic and acute MI. It has therefore the potential to serve as a surrogate end point to uncover advantages of new reperfusion strategies.