Estimation of the functional and anatomic extent of myocardial infarction using magnetic resonance imaging

Abstract This study assesses magnetic resonance (MR) imaging for the evaluation of both the functional and anatomic extent of damage to the left ventricle (LV) from myocardial infarction (MI). This was accomplished by blinded region-of-interest analysis of 36 MR examinations (orthogonal-transaxial, electrocardiographically-gated, multiphasic, single spin-echo) for determination of ejection fraction (EF) and relative MI volume (i.e., percent of total LV myocardial volume). Comparison of the results was then made with a measure of global residual LV function (i.e., score quotient or SQ) derived from segmental scoring of LV wall motion on a two-dimensional echocardiogram (Echo) and with an EF value from a left ventriculogram (LVG), both performed relatively concurrently with MR. Significant ( p r = 0.56) and LVG-EF ( r = 0.78), and these relationships were relatively stronger when MI was located in the right coronary artery (RCA) than when it was found in the left anterior descending (LAD) distribution (e.g., MR-EF compared with LVG-EF: r = 0.87, p r = 0.48, p = NS for LAD). The best expression of relative MI volume appeared to be based upon absolute volume of regionally-thinned LV wall multiplied by a correction factor for its residual contractility and then the addition of a volume correcting for the amount of regional wall thinning by necrosis (i.e., “total-Fxn” MI volume). The overall correlations between “total-Fxn” MI volume and both Echo-SQ ( r = 0.73) and LVG-EF ( r = 0.86) were significant ( p r = 0.64, p r = 0.93, p r = 0.02, p = NS, and r = 0.47, p = NS, respectively). Regional differences in the results are probably at least partially related to limitations with orthogonal-transaxial imaging. For the evaluation of both functional and anatomic extent of MI, MR imaging (transaxial, multiphasic) is valuable, but its relative value varies between regions of the LV.