title: Acute Effects of Pacing at Different Ventricular Sites on Left Ventricular Rotational Mechanics in a Porcine Model.
abstract: OBJECTIVE
  The purpose of this study was to examine the acute effects of pacing at different ventricular sites on hemodynamics and left ventricular (LV) rotational mechanics using speckle-tracking echocardiography (STE) in a porcine model.
  
  
  METHODS
  A prospective laboratory investigation.
  
  
  METHODS
  University research laboratory.
  
  
  METHODS
  Yorkshire pigs.
  
  
  METHODS
  In 9 pigs, after midline sternotomy, epicardial pacing was performed from the right ventricular outflow tract (RVOT), right ventricular apex (RVA), and LV free wall.
  
  
  RESULTS
  Two-dimensional STE and conductance catheter-derived LV pressure-volume measurements were made to determine the impact of pacing from various sites on LV rotational parameters (twist/untwist) and hemodynamics. RVOT pacing caused the least decrease in end-systolic pressure from baseline (-9.5%), when compared with RVA (-19.1%) and LV (-23.4%). Systolic and diastolic parameters (Emax, Tau) also were different among RVOT (4.7±0.8 mmHg/mL, 32±4 ms), RVA (3.9±0.7 mmHg/mL, 37±6 ms), and LV sites (3.6±0.8 mmHg/mL, 42±7 ms). Similar to the effects of pacing on hemodynamics, RVOT pacing better preserved LV twist (11.1±1.8 v 8.6±1.7, 5.9±0.7 °) and untwisting rate (64.6±8.5 v 56.2±5.3, 48.2±8.5 °/s) when compared with RV apical pacing and LV pacing. Furthermore, prolongation of conduction from LV lateral to anteroseptal at LV base (26.5±3.8 v 13.8±3.3 ms, p<0.05) and LV midpapillary muscle level (35.6±5.6 v 14.1±2.4 ms, p<0.05) was observed with LV pacing compared with RVOT pacing.
  
  
  CONCLUSIONS
  The present data showed that the LV twist/untwist and cardiac systolic and diastolic function were least affected by RVOT pacing. This finding may be explained by the proximity of this location to the native ventricular conduction system.
authors.affiliation: Departments of *Anesthesiology.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhou
authors.affiliation: Cardiovascular Surgery, University of California Los Angeles, Los Angeles, CA.
authors.forename: Peyman
authors.initials: P
authors.lastname: Benharash
authors.affiliation: Departments of *Anesthesiology.
authors.forename: Jason Han
authors.initials: JH
authors.lastname: Chua
authors.affiliation: Dokkyo Medical University, Tochigi, Japan.
authors.forename: Shiro
authors.initials: S
authors.lastname: Nakahara
authors.affiliation: Departments of *Anesthesiology.
authors.forename: Jonathan K
authors.initials: JK
authors.lastname: Ho
authors.affiliation: Departments of *Anesthesiology. Electronic address: amahajan@mednet.ucla.edu.
authors.forename: Aman
authors.initials: A
authors.lastname: Mahajan
mesh_terms: D000818:Animals; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D006352:Heart Ventricles / Q000000981:diagnostic imaging; D006439:Hemodynamics / Q000502:physiology; D011446:Prospective Studies; D013552:Swine; D014463:Ultrasonography; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D016277:Ventricular Function, Left / Q000502:physiology*
keywords: LV twist; pacing site; synchrony; ventricular tachycardia