(26)
In our study; programming the pacemakers from AS-VP mode (group I) to
AP-VP mode at rate of 100 b/min in (group II) showed a significant
decrease in both global and regional LV LSS.
Hettrick et al observed that atrial pacing has been shown to
reduce overall LV stroke volume due to impaired filling caused by atrial
dysfunction. (27) In Liang et al .
study, atrial pacing in DDD mode resulted in sub-optimal ventricular
diastolic filling and consequently stroke volume compared to intrinsic
atrial derived rhythm in VDD mode. In addition, they also demonstrated
atrial mechanical dysfunction reflected by decreased active atrial
strain caused by atrial pacing in DDD mode.(25) In their study, although LVEF was not
statistically different between VDD (ventricular only pacing) and DDD
(dual chamber pacing) modes, the more sensitive strain measurements
demonstrated statistically significant differences in global strain of
LV. This indicated that LV systolic function is indeed lower in DDD mode
due to direct deleterious effect of atrial pacing on the atrium leading
to indirect effects on the LV strain. Therefore, they concluded that
atrial pacing in DDD mode led to atrial dysfunction causing decreased LV
preload and consequently reduced LV systolic mechanics, resulting in
sub-optimal LV performance when compared to VDD mode.