Ventricular Effective Refraction Period and Ventricular Repolarization Analysis in Experimental Tachycardiomyopathy in Swine.
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.


OBJECTIVES
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).


MATERIAL AND 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.
['Noszczyk-Nowak|Agnieszka|A|', 'Pasławska|Urszula|U|', 'Gajek|Jacek|J|', 'Janiszewski|Adrian|A|', 'Pasławski|Robert|R|', 'Zyśko|Dorota|D|', 'Nicpoń|Józef|J|']
D000818:Animals D001145:Arrhythmias, Cardiac D002304:Cardiac Pacing, Artificial D009202:Cardiomyopathies D004452:Echocardiography D004562:Electrocardiography D022062:Electrophysiologic Techniques, Cardiac D055724:Electrophysiological Phenomena D005260:Female D006329:Heart Conduction System D006352:Heart Ventricles D006801:Humans D008297:Male D013552:Swine D017180:Tachycardia, Ventricular D013997:Time Factors
repolarization tachycardiomyopathy swine pacemaker refractory period