Abstract 15897: Optimizing Biventricular Pacing During Right Ventricle Pressure Overload Acutely Improves Mechanical Dyssynchrony and Function by 2-D Speckle Tracking
Background: Optimizing biventricular pacing (BiVP) with RV-first pacing increases cardiac output in acute RV pressure overload (RVPO). We tested the hypothesis that regional LV strain measurements would also show corresponding improvements.
Methods: Complete heart block and RVPO were induced in five open-chest pigs. In BiVP, cardiac output was optimized by aortic flow probe by adjusting atrio-ventricular and right-left ventricle delays. Speckle tracking was applied to 6 segments in mid-LV short axis views in atrio-RV pacing (RVP), atrio-LV pacing (LVP) and BiVP. Intraventricular synchrony was assessed by time to peak (TTP) strain difference between anterior septal and posterior walls and function by radial strain.
Results: In all cases BiVP optimized cardiac output with RV-first pacing. Cardiac output was higher with BiVP compared to LVP (0.96±0.26L/min vs. 0.89±0.27L/min; p=0.05). Anterior septal TTP strain was significantly prolonged during LVP vs. BiVP and RVP (502±19ms vs. 392±58ms and 390±53ms, respectively; p=0.0018). Posterior wall segment TTP strain preceded anterior septal during LVP (Anterior Septal: 502±19ms and Posterior: 396±72ms; p=0.0011) leading to a 106ms opposing wall difference, with no significant difference during BiVP or RVP (figure 1). Strain was 66% higher in posterior than the anterior septum during BiVP (Posterior: 20±5% and Anterior Septal: 12±6% p=0.0029) and RVP (Posterior: 20±3% and Anterior Septal: 12±7% p=0.0002), compared to LVP (figure 2).
Conclusions: RV pre-excitation unloads the high pressure state of the RV, reducing the duration of anterior septal wall contraction and allowing for greater LV synchrony and function.
- © 2010 by American Heart Association, Inc.