The Value of Functional Fascicular Block in Patients With Atrioventricular Re-Entrant Tachycardia
Satoshi Higuchi1, Edward P Gerstenfeld2, Adam C Lee3
1Section of Cardiac Electrophysiology, Division of Cardiology, University of California-San Francisco, San Francisco, California, USA; Clinical Research Division for Heart Rhythm Management, Tokyo Women's Medical University, Tokyo, Japan. Electronic address: https://twitter.com/satoshihgc.
Background:
Changes in retrograde conduction time (Δ ventriculoatrial interval [ΔVAI]) during functional complete bundle branch block (BBB) have been well established for localizing the accessory pathway (AP) in atrioventricular re-entrant tachycardia (AVRT).
Objectives:
This study investigated whether ΔVAI during functional fascicular block (FB) provides more detailed AP localization and the significance of incomplete BBB in AVRT.
Methods:
A total of 419 patients (age 22 ± 16 years; 39% male) with single non-decremental APs (left free wall, n = 207; septal, n = 159; and right free wall, n = 53) displaying functional FB (left anterior FB [LAFB], n = 66; left posterior FB [LPFB], n = 43) or BBB (right BBB, n = 183; left BBB, n = 136) during AVRT were studied. ΔVAI was evaluated during FB, including isolated LAFB or LPFB, and during BBB, distinguishing between complete (QRS ≥120 milliseconds) or incomplete (QRS <120 milliseconds) BBB associated with each AP location.
Results:
In patients with left free wall APs and right free wall APs, ΔVAI increased with ipsilateral BBB. Complete BBB served to better distinguish AP location compared with incomplete BBB. LAFB produced ΔVAI prolongation with left lateral and posterior-lateral APs, whereas no ΔVAI was observed with left posterior and posterior-septal APs. In contrast, LPFB produced marked ΔVAI lengthening with left posterior, posterior-lateral, and posterior-septal APs, whereas no ΔVAI was observed with left lateral APs.
Conclusions:
In patients with AVRT, ΔVAI during complete BBB enables more robust AP localization compared with incomplete BBB. Moreover, ΔVAI during FB allows for AP localization along the mitral annulus, especially LAFB for left lateral APs and LPFB for posterior-septal and left posterior APs.
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