Effects of ablation, digitalis, and beta-blocker on dual atrioventricular nodal pathways and conduction during atrial fibrillation.
BACKGROUND
Modification of AV nodal conduction by radiofrequency ablation (RFA) results in a variable reduction in heart rate during atrial fibrillation (AF). Using AF induced in patients with dual AV nodal pathways as a model, we tested the effect of additional treatment with digitalis (ouabain) and beta-blocker (esmolol).


RESULTS
Ten patients were randomized to control (group I) and studied only before ablation. AF was induced in 30 patients before and after slow pathway ablation (group II). Mean ventricular cycle lengths (AF CLmean) were recorded. Slow pathway conduction was eliminated after ablation in 10 patients (group IIA), whereas slow pathway conduction was still present in 20 patients (group IIB). Compared to pre-RFA there was a 10% increase in AF CLmean post-RFA (P < 0.01). During isoproterenol infusion the increase was 8% (P = NS). Adding digitalis and beta-blocker during isoproterenol infusion increased AF CLmean by 75% (95% in group IIA) compared to 36% in group I (P < 0.001 II vs I).


CONCLUSIONS
Slow pathway ablation reduces ventricular rate during AF. Addition of digitalis and beta-blocker during isoproterenol infusion significantly decreases ventricular rate after ablation compared to the control group. The finding suggests that beta-blocker has significant effects on fast AV nodal pathway conduction during induced AF with isoproterenol infusion.
Hegbom
Finn
F
Heart & Lung Center, Ullevål University Hospital, Oslo, Norway. finn.hegbom@IOKS.uio.no
Orning
Otto M
OM
Heldal
Magnus
M
Gjesdal
Knut
K
D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use*; D001281:Atrial Fibrillation / Q000139:chemically induced / Q000503:physiopathology* / Q000628:therapy*; D001283:Atrioventricular Node / Q000187:drug effects / Q000502:physiology*; D017115:Catheter Ablation; D004071:Digitalis Glycosides / Q000627:therapeutic use*; D005260:Female; D006329:Heart Conduction System / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007545:Isoproterenol; D008297:Male; D008875:Middle Aged
D000319:Adrenergic beta-Antagonists; D004071:Digitalis Glycosides; D007545:Isoproterenol