Change with exercise in QT dispersion in infarct-related myocardium after angioplasty

Background: The aim of this study was to evaluate the relationship between exercise-induced QT dispersion and condition of infarct-related myocardium including myocardial scar after angioplasty assessed with exercise perfusion single photon emission computed tomography (SPECT). Methods: Exercise thallium-201 SPECT was performed 6 months after successful direct angioplasty in 67 male patients (60.6±11.5 years), who had Q wave infarction resulting from single vessel disease, and the number of perfusion defect areas (DS) was measured at rest and exercise together with QT (QTc) dispersion. Results: In 52 patients with resting perfusion defects, the exercise-induced change in DS was correlated to the change in QT (or QTc) dispersion (r=−0.51 or r=−0.531, p<0.0001). When the patients were grouped according to the patterns of transient perfusion defect, there were significant differences in ΔQT dispersion and ΔQTc dispersion among infarct-related three groups (reverse, fixed, and partial redistributions) and normal volunteers (ΔQT dispersion; −5.7±12.7 ms in 13 patients with reverse redistribution, −16.3±13.1 ms in 30 patients with fixed redistribution, −28.9±29.5 ms in 9 patients with partial redistribution, and +3.4±20.9 ms in 12 normal volunteers, p=0.0098; ΔQTc dispersion; +18.2±20.8 ms, +1.4±16.7 ms, −15.4±30 ms, and +19±27.5 ms, p=0.0017, respectively). ΔQTc dispersion estimated the SPECT image patterns (p=0.0002) with a sensitivity of 67.3%, a specificity of 83.7% and an accuracy of 78.2%. Conclusions: The change with exercise in QT dispersion may help detect the condition of infarct-related myocardium after angioplasty.