CORRELATION OF THALLIUM UPTAKE WITH LEFT-VENTRICULAR WALL THICKNESS BY CINE MAGNETIC-RESONANCE-IMAGING IN PATIENTS WITH ACUTE AND HEALED MYOCARDIAL INFARCTS

Myocardial infarction (MI) is characterized by cellular necrosis which undergoes fibrotic transformation over time. Cine magnetic resonance imaging (MRI) offers high-resolution 3-dimensional images of the left ventricular myocardium, allowing sampling of the myocardial wall thick ness over the entire left ventricle. Tomographic (single-photon emissi on computed tomography [SPECT]) thallium images also provide 3-dimensi onal information on the location and level of thallium uptake, which h as been shown to correlate with myocardial viability. The purposes of this study were: (1) to examine the relation between bath end-diastoli c and end-systolic wall thickness and normalized thallium-201 uptake o ver the left ventricle in a group of patients with MI, (2) to examine the relation between regional wall thickening and normalized thallium uptake, and (3) to examine the relation between thallium uptake and wa ll thickness both early and late after infarction. Twenty-four patient s with MI underwent stress, redistribution, and reinfectian thallium S PECT imaging and cine MRI within several days. Seventeen patients unde rwent imaging late after infarction and 7 underwent imaging early afte r infarction. Normalized thallium activity was correlated with MRI wal l thicknesses at both end-diastole and end-systole for 18 segments for each ventricle. In addition, end-diastolic and end-systolic wall thic knesses were grouped by their corresponding thallium activity levels i nto percentiles. End-systolic wall thickness correlated significantly with normalized thallium uptake in 14 of 18 segments, end-diastolic wa ll thickness in only 4 of 18 segments, and wall thickening in only 3 o f 18 segments. Mean valves for end-diastolic and end-systolic wall thi cknesses corresponding to severely reduced (< 50%) normalized thallium activity were 9.9 +/- 1.1 and 8.5 +/- 0.6, respectively. Using receiv er-operating curve analysis, end-systolic wall performed as a better d iagnostic parameter than end-diastolic wall for identifying severely r educed thallium activity levels, For all levels of tfiallium activity, end-diastolic wall thicknesses were all thinner late versus early aft er MI, whereas end-systolic wall thickness was thinner only in the seg ments corresponding to severely reduced thallium activity. Based on th ese results, end-systolic wall thickness is the best noninvasive anato mic parameter of myocardial scar. (C) 1997 by Excerpta Medica, Inc.