Abstract 2911: The Long Term Mechanical Effects of Permanent Right Ventricular Pacing: The Effects of Pacing Site
Introduction Right ventricular apical (RVA) pacing is associated acutely with adverse effects on left ventricular (LV) synchrony. Short term hemodynamic studies demonstrate a small advantage of right ventricular outflow tract (RVOT) over RVA pacing. The long term benefit of RVOT over RVA pacing is uncertain however. Also the effect of RV pacing on left atrial (LA) function is unknown.
Long term RVOT pacing is associated with superior systolic LV function and synchrony to RVA pacing
The LV dyssynchrony induced by RV pacing adversely affects LA function
Methods We studied 57 patients (mean age 75±1.5 years, 33 male) who had undergone permanent pacing (31 RVOT and 26 RVA) over 30±1.3 months. A standardized echo protocol was performed during AV synchronous pacing and analyzed by an investigator blinded to lead position. Grey scale images for speckle tracking were acquired in 3 apical views. LV synchrony was measured by standard deviation of values for time-to-peak longitudinal 2D strain on an 18-segment model (2D DI). LA strain was measured using speckle tracking: a region of interest was marked on the left atrium in apical 4- and 2-chamber views and longitudinal strain values were averaged. Septal A’ was measured as the peak tissue velocity at the mitral annulus in late diastole. LA and LV volumes were measured by biplane method of discs.
Results RVOT and RVA groups were similar for baseline characteristics. RVA pacing was associated with inferior LV ejection fraction to RVOT pacing (52±2% v 60±1% p=0.0004) and greater LV dyssynchrony (2D DI 76±4ms v 65±3ms, p<0.05). In both groups the wavefront of mechanical activation propagated from the LV apex to the base but did so more rapidly with RVOT pacing. There was a negative linear association between 2D DI and both septal A’ and LA strain (r=0.26, p=0.04 and r=0.32, p=0.02 respectively). RVA pacing was associated with greater LA size than RVOT pacing (86±7 v 67±5mL, p=0.03).
Conclusions Long term RVOT pacing is associated with superior LV systolic function to RVA pacing and less dyssynchrony than RVA pacing, despite similar spatial patterns of mechanical activation. RVOT pacing is also associated with less adverse LA remodelling. LA function is inversely associated with LV dyssynchrony induced by pacing.