title: Ventricular Effective Refraction Period and Ventricular Repolarization Analysis in Experimental Tachycardiomyopathy in Swine.
abstract: BACKGROUND
  Swine are recognized animal models of human cardiovascular diseases. However, little is known on the CHF-associated changes in the electrophysiological ventricular parameters of humans and animals.
  
  
  OBJECTIVE
  The aim of this study was to analyze changes in the durations of ventricular effective refraction period (VERP), QT and QTc intervals of pigs with chronic tachycardia-induced tachycardiomyopathy (TIC).
  
  
  METHODS
  The study was comprised of 28 adult pigs (8 females and 20 males) of the Polish Large White breed. A one-chamber pacemaker was implanted in each of the 28 pigs. Electrocardiographic, echocardiographic and electrophysiological studies were carried out prior to the pacemaker implantation and at subsequent 4-week intervals. All electrocardiographic, echocardiographic and short electrophysiological study measurements in all swine were done under general anesthesia (propofol) after premedication with midazolam, medetomidine, and ketamine.
  
  
  RESULTS
  No significant changes in the duration of QT interval and corrected QT interval (QTc) were observed during consecutive weeks of the experiment. The duration of the QTc interval of female pigs was shown to be significantly longer than that of the males throughout the whole study period. Beginning from the 12th week of rapid ventricular pacing, a significant increase in duration of VERP was observed in both male and female pigs. Males and females did not differ significantly in terms of VERP duration determined throughout the whole study period. Ventricular pacing, stimulation with 2 and 3 premature impulses at progressively shorter coupling intervals and an imposed rhythm of 130 bpm or 150 bpm induced transient ventricular tachycardia in one female pig and four male pigs. One episode of permanent ventricular tachycardia was observed.
  
  
  CONCLUSIONS
  The number of induced arrhythmias increased proportionally to the severity of heart failure and duration of the experiment. However, relatively aggressive protocols of stimulation were required in order to induce arrhythmia in the studied pigs.
authors.affiliation: Department of Internal Medicine and Clinic of Diseases of Horses, Dogs and Cats, Faculty of Veterinary Medicine, Wroclaw University of Environmental and Life Sciences, Poland.|Regional Specialist Hospital in Wrocław, Research and Development Center, Poland.
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Noszczyk-Nowak
authors.affiliation: Department of Internal Medicine and Clinic of Diseases of Horses, Dogs and Cats, Faculty of Veterinary Medicine, Wroclaw University of Environmental and Life Sciences, Poland.|Regional Specialist Hospital in Wrocław, Research and Development Center, Poland.
authors.forename: Urszula
authors.initials: U
authors.lastname: Pasławska
authors.affiliation: Department of Cardiology, Wroclaw Medical University, Poland.
authors.forename: Jacek
authors.initials: J
authors.lastname: Gajek
authors.affiliation: Department of Internal Medicine and Clinic of Diseases of Horses, Dogs and Cats, Faculty of Veterinary Medicine, Wroclaw University of Environmental and Life Sciences, Poland.
authors.forename: Adrian
authors.initials: A
authors.lastname: Janiszewski
authors.affiliation: Department and Clinic of Internal and Occupational Diseases and Hypertension, Wroclaw Medical University, Poland.
authors.forename: Robert
authors.initials: R
authors.lastname: Pasławski
authors.affiliation: Department of Emergency Medicine, Wroclaw Medical University, Poland.
authors.forename: Dorota
authors.initials: D
authors.lastname: Zyśko
authors.affiliation: Department of Internal Medicine and Clinic of Diseases of Horses, Dogs and Cats, Faculty of Veterinary Medicine, Wroclaw University of Environmental and Life Sciences, Poland.|Regional Specialist Hospital in Wrocław, Research and Development Center, Poland.
authors.forename: Józef
authors.initials: J
authors.lastname: Nicpoń
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000503:physiopathology; D002304:Cardiac Pacing, Artificial; D009202:Cardiomyopathies / Q000503:physiopathology*; D004452:Echocardiography; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac / Q000379:methods; D055724:Electrophysiological Phenomena; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006352:Heart Ventricles / Q000503:physiopathology; D006801:Humans; D008297:Male; D013552:Swine; D017180:Tachycardia, Ventricular / Q000503:physiopathology*; D013997:Time Factors
keywords: pacemaker; refractory period; repolarization; swine; tachycardiomyopathy