Atrial fibrillation is associated with decreased cardiac sympathetic response to isometric exercise in CHF in comparison to sinus rhythm.
BACKGROUND
The presence of atrial fibrillation (AF) in congestive heart failure (CHF) is accompanied by increased mortality, although the exact mechanism is unclear. In previous studies, we have demonstrated cardiac baroreceptor abnormalities in association with AF and CHF. In this study, we sought to examine the effect of cardiac rhythm on the cardiac sympathetic response to exercise in CHF.


METHODS
In 13 CHF patients (six AF, seven SR, left ventricular ejection fraction 31 +/- 2%, age 61 +/- 1 years), we measured the hemodynamic and cardiac sympathetic response isometric handgrip (IHG) exercise.


RESULTS
At baseline the groups were well matched. Baseline hemodynamics and cardiac sympathetic activity did not significantly differ between the cohorts. In response to IHG exercise, both groups demonstrated significant hemodynamic responses. In conjunction, the sinus rhythm (SR) group demonstrated a significant increase in cardiac sympathetic response to exercise (P = 0.04) while in contrast the AF group did not (P = 0.6).


CONCLUSIONS
In this study, we demonstrate for the first time that the combination of AF and CHF is accompanied by a marked attenuation of the cardiac sympathetic response to acute hemodynamic stress. This implies AF is associated with a further impairment of baroreceptor response in CHF compared to SR. These findings present possible insights to the associated increased mortality and pathogenesis of AF with CHF.
Wynn Department of Metabolic Cardiology, Baker Heart Research Institute, Melbourne, Australia.
Paul A
PA
Gould
Murray D
MD
Esler
David M
DM
Kaye
D001281:Atrial Fibrillation / Q000175:diagnosis* / Q000503:physiopathology*; D001794:Blood Pressure; D005080:Exercise Test; D005260:Female; D006333:Heart Failure / Q000175:diagnosis* / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D008875:Middle Aged; D013564:Sympathetic Nervous System / Q000503:physiopathology*