Changes in QTs Interval and QT Dispersion due to Incremental Atrial Pacing in Patients with Ventricular Tachyarrhythmia

Abstract

This study was conducted to establish the relationship between QT dispersion and QT duration due to incremental atrial pacing. The QT interval and dispersion were measured in 47 patients. Sixteen of the patients had ventricular tachycardia or ventricular fibrillation (VT/ VF) [10 with organic heart disease (OHD) and 6 without OHD] . The control group was 31 patients (15 with OHD and 16 without OHD) . The QT interval was measured from a surface 12-lead electrocardiogram in sinus rhythm and during incremental atrial paced rates, and was calculated using Bazett's formula. Moreover, the QT interval was divided into the interval between the onset of the QRS and the peak of the T wave (QT peak) and the interval between the peak of the T wave and the end of the T wave (QT end) . QT dispersion at rest was markedly increased in the VT/ VF with OHD group compared with that in the controls and the VT/ VF without OHD group (172±97.2 vs 78±41.1 vs 56.7±39.3 vs 52.5±25.9 p< 0.05) . In VT/ VF patients with OHD, QT dispersion decreased up to 100 beats per minute (bpm) due to the incremental atrial pacing, but increased beyond 100 bpm. The QTc minimum (QTc min) interval did not change with any of the pacing rates. The interval between QT peak and QT end is a nucleus of the fluctuation of the dispersion by the heart rate. The QT dispersion of the VT/VF with OHD patient group responded to heart rate changes.