Effects of cardiac pacemakers on left ventricular volumes and function assessed by 3D echocardiography, Doppler...

Many previous studies reported the negative effects of right ventricular (RV) pacing on the left ventricular (LV) structure and ejection fraction. Studying pacing hemodynamics is essential to understand these detrimental effects. In this study, we tried to understand RV pacing effects on LV volumes and function using advanced tools like 3D echo and global longitudinal strain (GLS). This was a prospective study of 175 consecutive patients (LVEF>50%) presented permanent pacing. Of 175 patients, only 50 patients met study criteria, divided into two groups (single or dual pacing). LV volumes and function were assessed by full-volume 3D echocardiography and GLS before pacing, at 1-week and 6-month post-pacing. Cardiac output (COP) was calculated by pulsed wave Doppler method and 3D echo.

Doppler method results were similar to 3D echo in calculating SV and COP. At 1-week post pacing, both groups showed a significant decrease in SV due to a drop in EDV while ESV did not change significantly. Despite the drop in SV, there was a significant increase in cardiac output (COP) due to achieving higher heart rates post-pacing. There was a significant drop in EF and GLS in both groups. At 6 months, SV continued to decrease with a corresponding decrease in COP and LVEF. This drop in SV was due to a significant increase in ESV while EDV did not show a significant change at a 6-month follow-up. Also, the drop EF and GLS became more significant. There were no significant differences between both groups regarding the changes in LV volumes (EDV, ESV, SV), LVEF or GLS throughout the study (pre-pacing, at 1-week and 6-months post pacing). However, dual-chamber pacing group provided higher heart rates and as a result higher COP than the single-chamber group.

RV pacing led to a significant drop in LV COP, ejection fraction (EF), and GLS over short- and long-term duration. Dual chamber pacing provided higher COP than a single chamber pacing. This was due to tracking the S. A node with pacing at higher heart rates not due to an increase in SV and preserving atrioventricular synchrony. Both Doppler method and 3D echo can be used to calculate SV and COP.