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Figure 1 Electrophysiological Recordings of the Change From Sinus Rhythm to High-Septal Pacing
Electrophysiological recordings obtained from a single anesthetized dog in sinus rhythm (t = –2 weeks) (A), in atrially triggered high-septal pacing (VDD) directly after atrioventricular (AV)-nodal ablation (t = –2 weeks) (B), and in continued VDD pacing, 2 weeks after pacemaker implantation (t = 0 weeks) (C). In each panel, electrocardiographic (ECG) leads II and AVR and left (LV) and right ventricular (RV) monophasic action potential (LV and RV monophasic action potential [MAP], respectively) recordings are shown. From top to bottom are indicated: RT, QRS, RR, duration of LV and RV MAP, and activation time (all ms). Horizontal and vertical calibrations represent 1 s (paper speed 25 mm/s) and 1 mV for ECG recordings and 20 mV for monophasic action potential (MAP) signals. Altering origin of ventricular activation from AV nodal to high septal preserves QRS axis but increases QRS duration and alters activation time to negative values. In contrast, VDD pacing does not alter ventricular repolarization parameters.
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