Electrocardiographic changes during postnatal development in conscious swine with cardiac autonomic imbalance

Using a conscious swine model, we studied the effects of different patterns of cardiac autonomic denervation on alterations of R-R and Q-T intervals f or 8 postnatal weeks. Newborn pigs were assigned randomly to four different groups: sham-operated controls (C), stellate ganglion ablation (SGX), eith er left (LSGX) or right (RSGX), and the right cardiac vagus nerve (RCVX) tr ansection. The ECGs were recorded by telemetry while animals rested quietly or were judged behaviorally to he asleep. Analyses of the ECG included mea surements of R-R and Q-T intervals, as well as corrected Q-T intervals (QTc ). Poincare plots were used to display age-related differences in R-R and Q -T intervals. For stellectomized animals, significantly prolonged R-R inter vals were first observed at post-surgical week 3 in the RSGX group and at w eek 5 in the LSGX group. Significantly prolonged QTc was found only in the RSGX group. In the RCVX group, shortened QTc and R-R intervals were noted a t 6 and 7 weeks after denervation. Furthermore, three of six RSGX animals ( 50%) and one of four RCVX animals (25%) exhibited marked pauses in sinus rh ythm that were unrelated to changes in heart rare or to sinus arrhythmia. T hese results in conscious animals support our hypothesis that abnormal auto nomic innervation of the heart during maturation, e.g., withdrawal of vagal cardiac modulation or asymmetry of sympathetic innervation, impairs cardia c electrical stability. (C) 2001 Published by Elsevier Science B.V.