Clinical Electrophysiology -> Atrial Fibrillation & Atrial Flutter: -> Physiology D-PO03 - Poster Session III (ID 48) Poster

D-PO03-228 - Autonomic Dysregulation Of Cardiac Volume During AF In Comparison To Sinus Rhythm; Implications For Rhythm Control (ID 373)


Background: Patients with AF studied in sinus rhythm (SR) have impaired vasomotor response to decreased cardiac volume. The assessment of cardiovascular autonomic reflexes during AF is challenging.
Objective: To study haemodynamic responses during AF to lower body negative pressure (LBNP); which decreases cardiac volume, deactivates atrial stretch receptors and induces a reflex to maintain blood pressure by increasing vascular resistance (SVR).
Methods: We studied 23 consecutive patients with paroxysmal or persistent AF; during AF (n = 10) and SR (n = 13). Anti-arrhythmic/hypertensives were withheld. LBNP using a chamber to seal the lower limbs was applied at 0, -20 and -40 mmHg. Finger photo plethysmography was used for continuous blood pressure (BP). We measured forearm blood flow (FBF; inversely proportional to SVR) by forearm venous occlusion plethysmography (VOP) which gauges volume displacement due to arterial inflow. VOP is non-invasive, well validated and impervious to AF.
Results: Mean age in the AF group (63 ± 10 years) was similar to SR (57 ± 17; P = 0.4). Whilst resting mean BP (MBP) was similar (AF; 108 ± 26, SR; 95 ± 20: P = 0.2); HR was higher in the AF group (97 ± 20) vs. SR (60 ± 13: P <0.0001*). In response to LBNP; MBP was maintained in SR (- 0.1% ∆: P = 0.2) however it decreased during AF (- 4.7% ∆: P < 0.05*). HR response was different in SR (+ 10 ± 13 bpm) vs AF (- 3 ± 6 bpm: P = 0.02*). The reduction in FBF seen in SR (increased SVR due to vasoconstriction) was absent during AF. Figure 1.
Conclusion: AF is associated with the autonomic dysregulation of cardiac volume. This novel finding could explain falls and syncope due to AF and may also be implicated in atrial remodelling and thus, AF progression.