Circulation. 2003;107:1059.)
© 2003 American Heart Association, Inc.
Basic Science Reports
|
Youhua
Zhang, MD, PhD; Saroja Bharati, MD; Kent A. Mowrey, MS; Todor N. Mazgalev, PhD
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.).
Correspondence to Todor N. Mazgalev, PhD,
Research Institute FF1-02, The Cleveland Clinic Foundation, 9500 Euclid Ave, Cleveland, OH 44195. E-mail mazgalt@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.