LEFT VENTRICULAR SYSTOLIC FUNCTION IN SELECTIVE AND NONSELECTIVE HIS BUNDLE PACING – A PILOT ECHOCARDIOGRAPHIC STUDY

Background: His bundle pacing (HBP) physiologically activates the ventricles through the His-Purkinje system. However, in some patients (pts), a nonselective His bundle pacing (NSHP) rather than a selective one (SHP) is achieved. Little is known about the mechanical cardiac function in this particular situation.
Purpose: To perform a comparative assessment of the parameters of the left ventricular (LV) systolic function in pts with nonselective and selective HBP.
Methods: We prospectively enrolled 10 pts (81±5 years) with HBP in which both selective and nonselective pacing was possible. A comprehensive echocardiogram was performed in all pts in both pacing modalities including speckle tracking analysis. The LV dyssynchrony index (LVdys) was defined as the maximal delay in time-to-peak radial strain at the papillary muscle level. Longitudinal LVdys was measured in apical views as standard deviation of time-to-peak systolic strain in 12 basal segments (SD¬t12s).
Results: The standard parameters of LV morphology and systolic function were not significantly different between groups (similar LV end-diastolic volumes, EF, stroke volumes) as well as LV global longitudinal systolic strain, circumferential strain and torsion (p>0.2 for all). No differences in LVdys and SD¬t12s were noted (53±68 vs 64±76ms, p=0.23 and 60±10 vs 64±20ms, p=0.55). In pts with NSHP, significantly shorter time to peak systolic strain values were noted in the basal and partially in the mid segments of the septum, most likely due to capture of the basal ventricular septum myocytes (343±34ms vs 274±78ms, p 0.01, after RR adjustment 38±5% vs 30±8%, p 0.02).
Conclusions: No significant differences in parameters of the LV systolic function and mechanical dyssynchrony were noted between SHP and NSHP in a small group of pts, suggesting that mechanical synchrony is not impaired in NSHP.