Relation between postpacing T wave changes and myocardial scintigraphic characteristics in patients with ventricular demand pacemaker.

The aim of this study was to elucidate the cause of T wave changes after ventricular pacing using thallium 201 single photon emission computed tomography (Tl-SPECT). Tl-SPECT was performed in 20 patients with sick sinus syndrome who had negative T wave after ventricular pacing and had had a ventricular demand pacemaker (VVI) implanted. Patients who have stenotic coronary arteries were excluded from the study. From the analysis of Tl-SPECT, extent score was calculated as the ischemic region. Data in patients with SSS were compared with those in 20 normal controls (NC). Thallium perfusion defects in patients with VVI were observed and distributed mainly in apex and inferior regions on the polar map. The extent score in patients with VVI was significantly higher than that in NC (56.4 +/- 21.6% vs 3.2 +/- 6.4%, P < 0.01). The washout rate of thallium 201 in the defect area was significantly lower in patients with VVI than in NC (27.4 +/- 10.2% vs 46.8 +/- 12.3%, P < 0.01). These results suggest that T wave changes after ventricular pacing are closely related to myocardial ischemia.