Preserved parasympathetic cardiac innervation after atrioventricular node modification: evidence from circle maps of respiratory sinus arrhythmia.

Introduction: Respiratory sinus arrhythmia (RSA) and heart rate variability (HRV) are parameters of autonomic cardiac innervation. They decrease with age and after atrioventricular nodal modification (AVNM) suggesting vagal denervation in both situations. We hypothesized, however, that AVNM causes only a transient, functional decline in vagal activity, whereas aging causes permanent vagal denervation.