on February 3, 2003
Published online before print February 3, 2003, doi: 10.1161/01.CIR.0000051464.52601.F4
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Submitted on September 30, 2002
From the Cleveland Clinic Foundation, Cleveland, Ohio (Y.Z., K.A.M. T.N.M.), and the Heart Institute for Children, Hope Children's Hospital, Oak Lawn, Ill (S.B.). * To whom correspondence should be addressed. E-mail: mazgalt{at}ccf.org.
Background--Traditional tools to study dual-pathway atrioventricular nodal (AVN) electrophysiology are not applicable in subjects with permanent atrial fibrillation (AF). The presence of fast-pathway (FP) and slow-pathway (SP) wavefronts and their possible modification remain uncertain in this condition. We demonstrated previously that His electrogram (HE) alternans can determine whether the FP or the SP reaches the His bundle on a beat-by-beat basis. We have now applied this novel index to monitor dual-pathway conduction and the effects of SP modification during AF. Methods and Results--In 12 rabbit AVN preparations, HE alternans were confirmed during a standard A1A2 pacing protocol. During AF, in 9 of the 12 hearts, HE alternans indicated the presence of dual pathways. Successful SP modification guided by the HE alternans eliminated the SP, resulting in a predominantly FP conduction during AF in all hearts. This increased the average His-His interval (204±14 versus 276±51 ms, P<0.001). Morphological studies revealed that SP modification damaged only the posterior extension of the AVN. Conclusions--We have demonstrated for the first time in rabbits that HE alternans permit "visualization" of dual-pathway electrophysiology and confirmed the presence of both FP and SP wavefronts during AF. This novel index has been used in a selective SP ablation that resulted in a significant slowing of the ventricular rate. HE alternans provide a new insight into the mechanisms of AVN conduction and could guide AVN modification for ventricular rate control in AF clinically.
Revised on November 7, 2002
Accepted on November 8, 2002
His Electrogram Alternans Reveal Dual Atrioventricular Nodal Pathway Conduction During Atrial Fibrillation. The Role of Slow-Pathway Modification
Youhua Zhang MD, PhD,
Key words: fibrillation • atrioventricular node • His bundle • alternans • electrophysiology
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