Role of the atrioventricular node in atrial fibrillation: what have we learned from radiofrequency catheter modification of the atrioventricular junction in patients with refractory atrial fibrillation?

Determinants of ventricular rate during atrial fibrillation (AF) are controversial. Concealed conduction, summation, rate and irregularity of atrial impulses, pacemaker activity of the AV node, and the electrophysiologic parameters of AV nodal function may all contribute. Findings from series of patients who underwent AV nodal modulation suggest that AV nodal conduction plays some role in the ventricular response to AF. The data are consistent with the presence of dual (or more) atrionodal inputs that play a role in determining AV nodal conduction properties. The data also strongly support the role of summation rather than simple prolongation of refractory periods as a mechanism of ventricular rate control.