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

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).

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.

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 DeltaQT dispersion and DeltaQTc dispersion among infarct-related three groups (reverse, fixed, and partial redistributions) and normal volunteers (DeltaQT 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; DeltaQTc dispersion; +18.2 +/- 20.8 ms, +1.4 +/- 16.7 ms, -15.4 +/- 30 ms, and +19 +/- 27.5 ms, p = 0.0017, respectively). DeltaQTc 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%.

The change with exercise in QT dispersion may help detect the condition of infarct-related myocardium after angioplasty.