Detailed endocardial mapping accurately predicts the transmural extent of myocardial infarction

OBJECTIVES This study delineates between infarcts varying in transmurality by using endocardial electrophysiologic information obtained during cathete r-based mapping. BACKGROUND The degree of infarct transmurality extent has previously been l inked to patient prognosis and may have significant impact on therapeutic s trategies. Catheter-based endocardial mapping may accurately delineate betw een infarcts differing in the transmural extent of necrotic tissue. METHODS Electromechanical mapping was performed in 13 dogs four weeks after left anterior descending coronary artery ligation, enabling three-dimensio nal reconstruction of the left ventricular chamber. A concomitant reduction in bipolar electrogram amplitude (BEA) and local shortening indicated the infarcted region. In addition, impedance, unipolar electrogram amplitude (U EA) and slew rate (SR) were quantified. Subsequently, the hearts were excis ed, stained with 2,3,5-triphenyltetrazolium chloride and sliced transversel y. The mean transmurality of the necrotic tissue in each slice was determin ed, and infarcts were divided into <30%, 31% to 60% and 61% to 100% transmu rality subtypes to be correlated with the corresponding electrical data. RESULTS From the three-dimensional reconstructions, a total of 263 endocard ial points were entered for correlation with the degree of transmurality (4 .6 +/- 2.4 points from each section). All four indices delineated infarcted tissue. However, BEA (1.9 +/- 0.7 mV, 1.4 +/- 0.7 mV, 0.8 +/- 0.4 mV in th e three groups respectively, p < 0.05 between each group proved superior to SR, which could not differentiate between the second (31% to 60%) and thir d (61% to 100%) transmurality subgroups, and to UEA and impedance, which co uld not differentiate between the first (<30%) and second transmurality sub groups. CONCLUSIONS The degree of infarct transmurality extent can be derived from the electrical properties of the endocardium obtained via detailed catheter -based mapping in this animal model. (J Am Coll Cardiol 2001;37:1590-7) (C) 2001 by the American College of Cardiology.