Autonomic influence on atrial fibrillatory process: head-up and head-down tilting.
BACKGROUND
Changes in the autonomic nervous system (ANS) tone are present before, during, and after episodes of atrial fibrillation (AF). Atrial fibrillatory rate (AFR, the inverse of the atrial cycle length) has been used as a surrogate marker for local refractoriness and is a key characteristic of the fibrillatory process in patients with AF. Aim of this study is to assess changes in AFR, as an effect of autonomic balance change.


METHODS
Forty patients undergoing cardiac cardioversion for symptomatic persistent AF were included in the study. Surface ECG was recorded during rest, head-down (HDT, -30°), and head-up tilt (HUT, +60°). A median value of AFR was computed in each phase of the protocol.


RESULTS
AFR decreased during HDT compared to the baseline (B) condition in all patients but three (median AFR_B = 391 fpm vs. AFR_HDT = 377 fpm, p < .0001). HUT increased AFR, making it significantly higher than HDT and baseline conditions (median AFR_HUT = 396 fpm, p < .0001 vs. B and HDT). Heart rate (HR) increased during HUT, but had a heterogeneous behavior in the population during HDT: about one third of the patients had an HR lower during HDT than during baseline, whereas the remaining two third had an increase in HR during HDT.


CONCLUSIONS
Dominant sympathetic/vagal tone during HUT/HDT significantly affects AFR, increasing/decreasing in respect to baseline. It may be worth exploring the possibility that patients with AF of shorter duration can convert to sinus rhythm during HDT.
Department of Internal Medicine and Department of Clinical Physiology, Central Hospital Kristianstad, Kristianstad, Sweden.
Sten
S
Östenson
Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milano, Italy.
Valentina D A
VD
Corino
Department of Cardiology, Clinical Sciences and Center for Integrative Electrocardiology at Lund University (CIEL), Lund, Sweden.
Jonas
J
Carlsson
Department of Cardiology, Clinical Sciences and Center for Integrative Electrocardiology at Lund University (CIEL), Lund, Sweden.|Arrhythmia Clinic, Skåne University Hospital, Lund, Sweden.
Pyotr G
PG
Platonov
D001281:Atrial Fibrillation / Q000503:physiopathology* / Q000628:therapy; D001341:Autonomic Nervous System / Q000503:physiopathology*; D004554:Electric Countershock; D004562:Electrocardiography; D005260:Female; D018475:Head-Down Tilt / Q000502:physiology; D006325:Heart Atria / Q000503:physiopathology; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D056888:Patient Positioning / Q000379:methods; D011187:Posture / Q000502:physiology*
atrial fibrillation; atrial fibrillatory rate; autonomic nervous system; head-down tilt; head-up tilt