Differences in left ventricular dyssynchrony between high septal pacing and apical pacing in patients with normal left ventricular systolic function.

Background And Purpose: Permanent right ventricular apical pacing can result in heart failure due to ventricular mechanical dyssynchrony. The purpose of the study was to define differences in left ventricular dyssynchrony between high septal pacing and apical pacing using tissue Doppler imaging (TDI) and two-dimensional (2D) speckle-tracking echocardiography (STE).

Methods: The subjects were 60 patients with normal left ventricular systolic function who underwent implantation of a permanent pacemaker. Patients were divided into two groups with high septal pacing (n=36) and conventional right apical pacing (n=24). Left ventricular dyssynchrony was measured using TDI and 2D-STE. The time difference (TD) between the earliest and latest activated segments obtained from each systolic velocity curve by TDI was defined as TD-TDI. The time differences obtained from systolic strain curves obtained by 2D-STE were defined as TD-RS for radial strain, TD-CS for circumferential strain, and TD-LS for longitudinal strain.

Results: The high septal pacing group had significantly shorter TD-TDI (20.0+/-24.3ms vs. 59.7+/-43.0ms, p<0.0001), TD-RS (13.5+/-19.9ms vs. 45.8+/-24.6ms, p<0.0001), and TD-LS (42.7+/-22.0ms vs. 66.6+/-26.8ms, p=0.001) values compared to the apical pacing group. There was no significant difference in TD-CS between the two groups.

Conclusion: Left ventricular dyssynchrony was smaller in patients with high septal pacing. The results show that 2D-STE is useful for detection of differences in left ventricular mechanical dyssynchrony in patients with permanent pacemaker implantation, in addition to TDI.