Effects of metabolically ischemic, but viable, myocardium on QT dispersionin patients with acute myocardial infarction - A study with resting I-123-BMIPP/thallium-201 myocardial single-photon emission computed tomography

In chronic Q-wave myocardial infarction, QT dispersion is closely correlate d with infarct size, but this correlation has not been evaluated for acute myocardial infarction (AMI). The effects of abnormal fatty acid metabolism on QT dispersion were examined in 123 patients with AMI who underwent resti ng iodine-123-15-iodophenyl 3-methyl pentadecanoic acid (BMIPP)/thallium-20 1 (Tl-201) myocardial single photon emission computed tomography (SPECT) an d electrocardiographic analysis in the subacute phase. The relationship bet ween BMIPP and Tl-201 was defined as match when the total defect score for BMIPP was equal to or smaller than that for Tl-201, and as mismatch when th e total defect score for BMIPP was larger than that for Tl-201. Twenty-six patients (21%) demonstrated BMIPP-Tl-201 match and 97 (79%) demonstrated mi smatch. Infarct size was closely correlated with QT dispersion (r=0.67, p<0 .001) in patients with BMIPP-Tl-201 match, but weakly correlated (r=0.30, p <0.005) in patients with BMIPP-Tl-201 mismatch. For small infarctions, QT d ispersion was significantly larger in patients with BMIPP-Tl-201 mismatch t han in those with BMIPP-Tl-201 match (62+/-24 ms vs 41+/-18 ms, p=0.03), bu t did not differ between the 2 groups for large infarctions. This study sho ws that QT dispersion is influenced by infarct size and by the presence of metabolically ischemic but viable myocardium in patients with AMI.