Comparison of the acute effects of right ventricular apical pacing and biventricular pacing in patients with heart failure.

Objective: Upgrading to biventricular (BiV) pacing benefits heart failure patients with right ventricular (RV) apical pacing. However, the impact of switching from RV apical pacing to BiV pacing on the left ventricular (LV) function accompanied by changes in the QRS duration remains unknown. We aimed to investigate the effects of BiV pacing in heart failure patients under RV apical pacing.

Methods: In 37 patients with heart failure (LV ejection fraction: 22±9%), the maximum rate of LV pressure rise (LV dP/dtmax) and time constant of LV relaxation (tau) were determined in order to assess LV contractility and diastolic relaxation, respectively, under RV apical pacing and BiV pacing. Switching from RV pacing to BiV pacing, the QRS duration was shortened from 209±42 to 162±28 ms (p<0.001) and the LV dP/dtmax values were increased in all patients (+18.4±11.3%, p<0.001), whereas the LV tau values varied (-1.5±13.0%, p=0.723). Shortening of the QRS duration correlated with the increase in LV dP/dtmax (r=-0.689, p<0.001); however, it was not closely associated with the changes in LV tau.

Conclusions: Switching from RV apical pacing to BiV pacing improves the LV contractile function in proportion to the degree of QRS shortening. BiV pacing is recommended in patients with systolic heart failure and a prolonged RV-paced QRS duration.