Thallium-201 perfusion defects during right ventricular pacing in normal subjects

To study on the regional myocardial perfusion during right ventricular endocardial high rate pacing (150bpm) , thallium-201 (Tl-201) myocardial scintigraphies were performed during pacing and exercise as comparative study in 20 normal subjects. Echocardiogram (UCG) and electrocardiogram (ECG) were simultaneously recorded. Fourteen of these 20 subjects had low uptake of Tl-201 in the interventricular septum (IVS) during pacing, whereas none had low uptake of Tl-201 during exercise. The ratio of the Tl-201 uptake in the IVS to that in the posterolateral wall (PL) (Tl-201 uptake ratio) was significantly decreased during pacing compared to that during exercise (0.99 ± 0.09 (mean ± SD)vs 0.81 ± 0.18, p < 0.001). During pacing, without rate (%) in the IVS was significantly decreased compared to that in the PL (43 ± 12% vs 26± 13%