title: Speckle-tracking echocardiography elucidates the effect of pacing site on left ventricular synchronization in the normal and infarcted rat myocardium.
abstract: BACKGROUND
  Right ventricular (RV) pacing generates regional disparities in electrical activation and mechanical function (ventricular dyssynchrony). In contrast, left ventricular (LV) or biventricular (BIV) pacing can improve cardiac efficiency in the setting of ventricular dyssynchrony, constituting the rationale for cardiac resynchronization therapy (CRT). Animal models of ventricular dyssynchrony and CRT currently relay on large mammals which are expensive and not readily available to most researchers. We developed a methodology for double-site epicardial pacing in conscious rats. Here, following post-operative recovery, we compared the effects of various pacing modes on LV dyssynchrony in normal rats and in rats with ischemic cardiomyopathy.
  
  
  METHODS
  Two bipolar electrodes were implanted in rats as follows: Group A (n = 6) right atrial (RA) and RV sites; Group B (n = 7) RV and LV sites; Group C (n = 8) as in group B in combination with left coronary artery ligation. Electrodes were exteriorized through the back. Following post-operative recovery, two-dimensional transthoracic echocardiography was performed during pacing through the different electrodes. Segmental systolic circumferential strain (Ecc) was used to evaluate LV dyssynchrony.
  
  
  RESULTS
  In normal rats, RV pacing induced marked LV dyssynchrony compared to RA pacing or sinus rhythm, as measured by the standard deviation (SD) of segmental time to peak Ecc, SD of peak Ecc, and the average delay between opposing ventricular segments. LV pacing and, to a greater extend BIV pacing diminished the LV dyssynchrony compared to RV pacing. In rats with extensive MI, the effects of LV and BIV pacing were markedly attenuated, and the response of individual animals was variable.
  
  
  CONCLUSIONS
  Rodent cardiac pacing mimics important features seen in humans. This model may be developed as a simple new tool to study the pathophysiology of ventricular dyssynchrony and CRT.
authors.affiliation: Cardiac Arrhythmia Research Laboratory, Department of Physiology and Cell Biology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
authors.forename: Michal
authors.initials: M
authors.lastname: Mor
authors.affiliation: Cardiac Arrhythmia Research Laboratory, Department of Physiology and Cell Biology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
authors.forename: Wesam
authors.initials: W
authors.lastname: Mulla
authors.affiliation: Cardiac Arrhythmia Research Laboratory, Department of Physiology and Cell Biology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
authors.forename: Sigal
authors.initials: S
authors.lastname: Elyagon
authors.affiliation: Cardiac Arrhythmia Research Laboratory, Department of Physiology and Cell Biology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel; Department of Emergency Medicine, Recanati School for Community Health Professions, Faculty of Health Sciences and PREPARED Center for Emergency Response Research, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
authors.forename: Hovav
authors.initials: H
authors.lastname: Gabay
authors.affiliation: Cardiac Arrhythmia Research Laboratory, Department of Physiology and Cell Biology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
authors.forename: Shani
authors.initials: S
authors.lastname: Dror
authors.affiliation: Cardiac Arrhythmia Research Laboratory, Department of Physiology and Cell Biology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel; Division of Internal Medicine, Soroka University Medical Center, Beer-Sheva, Israel.
authors.forename: Yoram
authors.initials: Y
authors.lastname: Etzion
authors.affiliation: Cardiology Department, Soroka University Medical Center, Beer-Sheva, Israel.
authors.forename: Noah
authors.initials: N
authors.lastname: Liel-Cohen
mesh_terms: D000818:Animals; D002304:Cardiac Pacing, Artificial; D054326:Coronary Sinus / Q000000981:diagnostic imaging / Q000503:physiopathology; D004452:Echocardiography; D006325:Heart Atria / Q000000981:diagnostic imaging / Q000503:physiopathology; D006333:Heart Failure / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology; D006352:Heart Ventricles / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D008297:Male; D008955:Models, Cardiovascular; D009203:Myocardial Infarction / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D017202:Myocardial Ischemia / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013599:Systole