Pacemaker programming:
All patients underwent different programming modes for their devices and were thereby represented as 3 groups: group I (AS-VP mode): in atrial sensed and ventricular paced mode; the device sense the intrinsic atrial activity and pace the ventricles accordingly to maintain A-V synchrony, group II (AP-VP mode): in atrial paced and ventricular paced mode; the device was programmed to initiate atrial pacing at a rate of 100 b/min followed by ventricular pacing “maintaining A-V synchrony” and group III (VVI mode): in this mode, the atrial lead is switched off and the device functions as a single chamber pacemaker delivering ventricular pacing at 100 b/min dissociated from the intrinsic atrial activity i.e. asynchronous ventricular pacing mode.
2-D STE was used to measure the global and segmental systolic longitudinal strain of the LV walls in order to compare them between controls and patients during AS-VP mode (group I). We also compared LV LSS in the patients in the three pacing modes; group I (AS-VP mode), group II (AP-VP mode) and group III (VVI mode). The comparison of LV LSS between group (AS-VP) and group (AP-VP) was done to study the indirect effects of atrial pacing on LV LSS. The comparison of LV LSS between group (AP-VP) and group (VVI) was done to study the effects of A-V synchrony on LV LSS at the same heart rate of 100 b/min.