Abstract 2313: Atrial Fibrillation Augments Single-unit Sympathetic Nerve Activity
Background: Although prognosis of rate-control therapy in atrial fibrillation (AF) has recently been shown to be similar to that of rhythm-control therapy, the sympathetic neural activity in rate-controlled AF remained uncertain. We hypothesized that irregular R-R interval influenced sympathetic nerve function and that AF itself augmented sympathetic nerve activity.
Methods and results: In the present study, we measured single-unit muscle sympathetic nerve activity (single-unit MSNA) in 8 lone AF patients without rapid ventricular rate, and compared 8 age-matched healthy subjects. All patients with AF have normal left ventricular systolic function (Ejection fraction, 66.2 +/− 2.4 %). Heart rate in AF patients was 62.9 +/− 4.1 bpm, which was not different in healthy subjects (60.5 +/− 9.3 bpm). Multiunit MSNA analysis did not differ between two groups. However, resting single-unit MSNA in AF patients were significantly greater than that in control subjects (61.6+/−12.3 spikes/min, 24.9+/−6.0 spikes/min, p<0.01, respectively). During reduced diastolic arterial pressure with long RR interval in AF patients, firing patterns of single-unit spikes were significantly shifted toward multiple spikes within a given burst (p<0.05). The relationship between single-unit MSNA and R-R interval was significantly correlated in AF patients (r=0.53 +/− 0.1, P<0.01)
Conclusions: These results indicate that multiple firing of single-unit MSNA within a burst increase in rate-controlled AF patients, suggesting that AF augments sympathetic nerve activity and restoring regular sinus rhythm may be beneficial.