Localization of Left Free‐Wall and Posteroseptal Accessory Atrioventricular Pathways by Direct Recording of Accessory Pathway Activation

Abstract

With the advent of catheter ablation techniques, precise localization of accessory AV pathways (AP) assumes greater importance. In an effort to define the course of AP fibers, we attempted to record activation of 56 left free-wall and 23 posteroseptal APs in 62 patients undergoing electrophysiological study. The coronary sinus (CS) and great cardiac vein (GCV) were mapped using orthogonal catheter electrodes, which provide a recording dipole perpendicular to the AV groove. The tricuspid annulus (TA) was mapped using a 2 mm spaced octapolar electrode catheter. Potentials were considered to represent AP activation only if they could be dissociated from both atrial and ventricular activation by programmed stimulation. Orthogonal catheter electrodes in the CS and GCV were advanced beyond the site of earliest retrograde atrial activation and/or earliest antegrade ventricular activation in 45 of the 56 left free-wall APs, and AP potentials were recorded from 42 (93%). An oblique course was identified in 36 APs, with the ventricular insertion being recorded 4-30 mm (median 15 mm) distal or anterior to the atrial insertion. In three patients, antegrade and retrograde conduction proceeded over different (but close) parallel fibers. AP potentials were recorded from 19 of 23 posteroseptal pathways. Ten pathways (left posteroseptal) were recorded from the CS, beginning 5-11 mm (median 9 mm) distal to the os, with potentials extending 8-18 mm (median 11 mm) distally. Four pathways (mid-septal) were recorded along the TA, anterior to the CS ostium and posterior to the His bundle catheter. Five pathways (right posteroseptal) were recorded along the TA, directly opposite or immediately posterior to the CS ostium. One of the patients had both midseptal and left posteroseptal pathways and three patients had both right posteroseptal and left posteroseptal pathways. We conclude: 1) left free-wall APs transit the AV groove obliquely and may be comprised of multiple, closely spaced, parallel fibers; 2) the anatomical location of "posteroseptal" pathways is variable and the presence of fibers at multiple sites is common; and 3) direct recordings of AP activation facilitate tracking of the accessory pathway along its course from atrium to ventricle and help identify the presence of multiple fibers.

New catheter technique for recording left free-wall accessory atrioventricular pathway activation. Identification of pathway fiber orientation.

“…block.32 The absence of an increase in the ventriculoatrial interval may be explained by the observation that, in almost half of the patients with "posteroseptal" accessory pathways, accessory pathway potentials are recorded across the tricuspid anulus rather than from the coronary sinus. 29 The demonstration of significant lateral excursion in left free-wall accessory pathways seems consistent with what is known of the embryological development of the heart at the AV boundary. In the primitive, fused cardiac tube, circumferential rings of histologically distinct specialized tissue have been described that later contribute variously to the cardiac fibroskeleton and the several divisions of the specialized cardiac conduction system.33-38 In the course of looping of the primitive cardiac tube, the common atrial region migrates upward and posteriorly, coming to lie above and behind the primitive ventricle and bulbus cordis.…”

“…Viable islets of anatomic continuity along with developing left AV groove would then presumably be subject to the effects of torsion upon growth and would exhibit counterclockwise rotation from atrium to ventricle as viewed from the apex. As part of the developmental expansion of the primitive ventricle and bulbus cordis at the time of bulboventricular folding, the previously circumferential myogenic fibers are pulled diagonally toward the vortex, which in turn migrates distally and comes to form the apical 22,25,27,29,45 …”

Safety and Efficacy of Cryoablation of Accessory Pathways Adjacent to the Normal Conduction System

“…At fluoroscopy, the tip of the ablation catheter was seen to be in close proximity to the His‐bundle catheter. The septal region usually is defined as bounded superiorly by the His bundle and inferiorly by the roof of the coronary sinus 17 . Dividing this area into three parts, para‐Hisian APs occupy the superior third of this area (Figs.…”

Management of the Patient with the Wolff-Parkinson-White Syndrome

“…Alternative energy forms, particularly radiofrequency current, may prove to be safer. This, coupled with more precise localization of the acces sory pathway using direct accessory pathwaypotential recordings, and approaching left sided pathways across the atrial septum or retrograde aortic arch/left ventricle catheter ization, may result in higher success [30]. Recently, Warin et al [52] have reported successful catheter ablation of accessory pathways utilizing a direct approach and DC energy in 32 of 35 patients.…”

“…Accessory pathways may be most accu rately localized by the direct recording of an accessory pathway potential. This requires the use of catheters with closely spaced elec trode pairs [29,30],…”