Effects of Metabolically Ischemic, But Viable, Myocardium on QT Dispersion in Patients With Acute Myocardial Infarction

- A Study With Resting I-123-BMIPP/Thallium-201 Myocardial Single-Photon Emission Computed Tomography -

Abstract

In chronic Q-wave myocardial infarction, QT dispersion is closely correlated 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 resting iodine-123-15-iodophenyl 3-methyl pentadecanoic acid (BMIPP)/thallium-201(²⁰¹Tl) myocardial single photon emission computed tomography (SPECT) and electrocardiographic analysis in the subacute phase. The relationship between BMIPP and ²⁰¹Tl was defined as match when the total defect score for BMIPP was equal to or smaller than for ²⁰¹Tl, and as mismatch when the total defect score for BMIPP was larger than that for ²⁰¹Tl. Twenty-six patients (21%) demonstrated BMIPP-²⁰¹Tl match and 97 (79%) demonstrated mismatch. Infarct size was closely correlated with QT dispersion (r=0.67, p<0.001) in patients with BMIPP-²⁰¹Tl match, but weakly correlated (r=0.30, p<0.005) in patients with BMIPP-²⁰¹Tl mismatch. For small infarctions, QT dispersion was significantly larger in patients with BMIPP-²⁰¹Tl mismatch than in those with BMIPP-²⁰¹Tl match (62±24 ms vs 41±18 ms, p=0.03), but did not differ between the 2 groups for large infarctions. This study shows that QT dispersion is influenced by infarct size and by the presence of metabolically ischemic but viable myocardium in patients with AMI.