title: Effects of biventricular pacing on left heart twist and strain in a porcine model of right heart failure.
abstract: BACKGROUND
  Biventricular pacing (BiVP) improves cardiac output (CO) in selected cardiac surgery patients, but response remains variable, necessitating a better understanding of the mechanism. Accordingly, we used speckle tracking echocardiography (STE) to analyze BiVP during acute right ventricular pressure overload (RVPO).
  
  
  METHODS
  In nine pigs, the inferior vena cava (IVC) was snared to decrease CO and establish a control model. Heart block was induced, the pulmonary artery snared, and BiVP initiated. Echocardiograms of the left ventricular midpapillary level were taken at varying atrioventricular delay (AVD) and interventricular delay (VVD) for STE analysis of regional circumferential strain (CS) and radial strain (RS). Echocardiograms were taken of the left ventricular base, midpapillary, and apex during baseline, IVC occlusion, and each BiVP setting for STE analysis of twist, apical and basal rotations, CS, RS, and synchrony. Indices were correlated against CO with mixed linear models.
  
  
  RESULTS
  During IVC occlusion, CO correlated with twist, apical rotation, RS, RS synchrony, and CS (P < 0.05). During RVPO with BiVP, CO only correlated with RS synchrony and CS (P < 0.05). During AVD and VVD variations, CO was associated with free wall RS (P < 0.008). CO correlated with septal wall CS during AVD variation and free wall CS during VVD variation (P < 0.008).
  
  
  CONCLUSIONS
  In an open chest model, twist, RS, RS synchrony, and CS analyzed by STE may be noninvasive surrogates for changes in CO. During RVPO, changes in RS synchrony and CS with varying regional strain contributions may be the primary mechanism in which BiVP improves CO. Lack of correlation of remaining indices may reflect postsystolic function.
authors.affiliation: Department of Surgery, Columbia Presbyterian Medical Center, New York, New York; Department of Surgery, Duke University Medical Center, Durham, North Carolina.
authors.forename: Alice
authors.initials: A
authors.lastname: Wang
authors.forename: Santos E
authors.initials: SE
authors.lastname: Cabreriza
authors.forename: Vinod
authors.initials: V
authors.lastname: Havalad
authors.forename: Linda
authors.initials: L
authors.lastname: Aponte-Patel
authors.forename: Gerardo
authors.initials: G
authors.lastname: Gonzalez
authors.forename: Bryan
authors.initials: B
authors.lastname: Velez de Villa
authors.forename: Bin
authors.initials: B
authors.lastname: Cheng
authors.forename: Henry M
authors.initials: HM
authors.lastname: Spotnitz
mesh_terms: D000818:Animals; D002302:Cardiac Output / Q000502:physiology; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D004195:Disease Models, Animal; D004452:Echocardiography / Q000379:methods; D006327:Heart Block / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000628:therapy*; D006333:Heart Failure / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000628:therapy*; D006976:Hypertension, Pulmonary / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology; D013552:Swine; D054159:Torsion, Mechanical; D014682:Vena Cava, Inferior / Q000503:physiopathology; D017725:Ventricular Pressure / Q000502:physiology
keywords: Biventricular pacing; Right ventricular pressure overload; Speckle tracking echocardiography
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