Circulation, Vol 90, 884-894, Copyright © 1994 by American Heart Association
R Cappato, M Schluter, L Mont and KH Kuck
BACKGROUND: The use of bipolar endocardial electrogram characteristics to
guide radiofrequency (RF) current catheter ablation of accessory pathways
(APs) has been advocated by several investigators. However, the influences
of a varying anatomy of the AP and the atrioventricular groove, of
different ablative approaches, and of RF current pulses preceding the final
pulse have not been adequately addressed. METHODS AND RESULTS: Local
bipolar endocardial electrograms were retrospectively analyzed in a uniform
cohort of 62 consecutive patients with a single manifest AP located on the
left free wall; in all patients, the AP had been ablated by a uniform
approach with a single catheter advanced retrogradely toward the mitral
annulus. Electrogram parameters assessed were the presence or absence of a
presumed AP potential, the atrial-to-ventricular (A/V) amplitude ratio, the
A-V interval, and the onset of delta wave to local ventricular activation
(delta-V) interval. The AP location was classified on fluoroscopy as
anterior, lateral, or posterior. Catheter stability was verified by
comparing pre- and post-RF amplitudes of local atrial potentials. The
ablation site was ventricular in 52 patients (group A) and atrial in 10
(group B). In group A, 26 APs (50%) required a single RF current pulse for
ablation. These APs showed no anatomic predilection and no statistically
significant differences in electrogram parameters from 24 APs that were
ablated only after a median of three pulses had failed, suggestive of a
wider ventricular insertion of the latter APs. A lower A/V ratio and a
higher incidence of transient AP block found in the remaining 2 group A
patients, who had anteriorly located APs requiring > 10 failed pulses,
suggested an adverse anatomy of the A-V groove in that region. A stepwise
multivariate logistic regression analysis revealed that the simultaneous
presence of (1) a presumed AP potential, (2) an A/V ratio > or = 0.10,
(3) an A-V interval < or = 40 milliseconds, and (4) a delta-V interval
< or = 0 milliseconds was associated with a specificity of 94% and a
positive predictive accuracy of 87% for an RF pulse to be successfully
applied to the ventricular insertion to the AP. Compared with APs of group
A, APs of group B were distinguished by unsuccessful ventricular pulses
associated with a delta-V interval > 10 milliseconds in the presence of
an A/V ratio > 0.33 (specificity of 97% and positive predictive accuracy
of 82%), which is suggestive of a more epicardial ventricular insertion of
these APs. CONCLUSIONS: The effect of anatomic variations of the AP and the
A- V groove is reflected in the bipolar endocardial electrogram and needs
to be considered in the approach to AP ablation. The stepwise inclusion of
the four electrogram criteria introduced in this study may improve the
efficacy of RF catheter ablation of a manifest left free-wall AP at its
ventricular insertion. Whenever mapping cannot improve on a delta-V
interval > 10 milliseconds despite apparently close contact with the
mitral annulus ("good" A/V ratio), attempts at ablation are likely to be
successful at the atrial aspect of the mitral annulus.
ARTICLES
Anatomic, electrical, and mechanical factors affecting bipolar endocardial electrograms. Impact on catheter ablation of manifest left free-wall accessory pathways
Department of Cardiology, University Hospital Eppendorf, Hamburg, Germany.
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