Abstract 5838: Arterial Baroreflex Control of Single-unit Muscle Sympathetic Nerve Activity in Chronic Heart Failure With Atrial Fibrillation
Prognosis of rate-control therapy in congestive heart failure (CHF) with atrial fibrillation has been shown to be similar to that of rhythm-control therapy. We reported that blood pressure changes induced by AF demonstrated major determinations of sympathetic nerve activity via arterial baroreflex. Sympathetic augmentation in CHF is assumed to be attributed to impaired baroreflex function. We hypothesized irregular R-R interval accompanying AF might not activate sympathetic nerve activity in CHF. In 35 closely age matched subjects with CHF (n=10), AF (n=11), CHF with AF (n=8) and healthy subjects (n=8), we measured resting multi-unit and single-unit muscle sympathetic nerve activity (MSNA). The single-unit MSNA in CHF with AF (61.6 +/− 12.3 spikes/min) was significantly greater (p<0.05) than that in CHF (46.4 +/− 9.3 spikes/min) and AF (38.6 +/− 14.5 spikes/min), and all these were significantly greater (p<0.01) than in healthy subjects (21.9±7.3 spikes/min). The multi-unit MSNA in CHF with AF was similar to that in CHF. Multiple firing of single-unit MSNA within one cardiac interval was augmented in AF groups (with or without CHF), especially during preceding long R-R interval and reduced diastolic pressure (p<0.05). The firing characteristics of sympathetic out flow were different between AF and sinus rhythm in both groups. Frequency of single-unit MSNA was augmented in CHF with AF. These results indicate that therapy for AF in CHF would be required to prevent sympathetic augmentation.