QT dispersion has been proposed as a noninvasive measurement of the degree of inhomogeneity เท myocardial repolarization. Increased QT dispersion has been reported after myocardial ischemia. We investigated whether QT dispersion at baseline and after dipyridamole injection correlate with the imaging patterns obtained from dipyridamole stress tecnitium-99 MIBI single photon emission computed tomography (dipyridamole SPECT). Method and Results: QT dispersion was determined in 56 patients who underwent dipyridamole-SPECT from 12-lead electrocardiograms obtained at baseline and 8 minutes after beginning of dipyridamole injection. Based on the results of dipyridamole-SPECT, patients were divided into 2 groups: negative and positive group. Baseline QT dispersion in both groups were 37.3 ± 14.0 and 43.3 ± 17.4 ms, respectively. QT dispersion after injection of dipyridamole were 43.2 ±16.0, 59.7 ± 25.8 ms, respectively. Baseline QT dispersion and QT dispersion after dipyridamole injection were significantly greater in the group with positive for dipyridamole-SPECT. The change of QT dispersion before and after dipyridamole injection is significantly greater in patient with positive for dipyridamole-SPECT compared with patients with negative for dipyridamole-SPECT (5.9±10.3, 16.5±16.8 ms, p=0.032). These findings suggest that the change in QT dispersion before and after dipyridamole injection is significantly greater in patient with ischemic heart disease. But it is not very sensitive and specific for use as diagnostic tool for detecting myocardial ischemia.
