Changes in R-R and Q-T intervals following cardiac vagotomy in neonatal swine

Asymmetric innervation of the myocardium, especially a predominance of symp athetic innervation, may establish conditions whereby electrical instabilit y could result. Using a swine animal model, we studied the effect of right cardiac vagal denervation on the variability of R-R and Q-T intervals. Newb orn pigs were assigned randomly to two groups: sham-operated controls (C), or denervation of the right cardiac vagus nerve (RCVX). EKGs were recorded weekly until the two groups exhibited significant heart rate differences. A nalysis of the EKG included measurements of R-R and Q-T intervals and corre cted Q-T intervals (QTc). Poincare plots were used to display age-related d ifferences in R-R and Q-T intervals. For RCVX animals, decreased QTc and R- R intervals were noted at 6 and 7 weeks after denervation, respectively. Un expectedly, one RCVX animal exhibited marked sudden pauses in sinus rhythm. These data indicated that reduced vagal cardiac modulation during developm ent might alter cardiac electrical stability in conscious swine.