Impact of bundle branch block morphology on outcomes of patients with syncope and bifascicular block: A SPRITELY (POST 3) substudy

Published:September 28, 2022DOI:


      Permanent pacing is often considered for patients with syncope and bifascicular block.


      The purpose of this study was to determine whether QRS morphology or other electrocardiographic characteristics can identify patients who may benefit from permanent pacing.


      The Syncope: Pacing or Recording in the Later Years (SPRITELY) trial was a multicenter trial that randomized patients with bifascicular block and syncope (n = 115) to empiric pacemaker implantation vs implantable loop recorder (ILR) monitoring. In this SPRITELY subanalysis, baseline 12-lead electrocardiograms were evaluated for bundle branch block (BBB) morphology, QRS width, and PR and QT intervals and their impact on clinical outcomes was assessed.


      There were 41 patients with left BBB (36%), 69 patients with right bundle branch block (RBBB) and left anterior fascicular block (60%), and 5 patients with RBBB and left posterior fascicular block (4%). Pacemaker implant compared with ILR was associated with a significant reduction of major study-related events (MSREs) in both patients with left BBB (23.8% vs 78.9%; P = .001) and those with RBBB (27% vs 72.9%; P < .0001). Similarly, a reduction of MSREs was observed in both patients with trifascicular block (23% vs 84.6%; P < .0001) and those with bifascicular block (26.6% vs 68.9%; P = .002). In the group randomized to ILR monitoring, the type of BBB was not a predictor of recurrent syncope (P = .30), bradycardia requiring pacemaker (P = .15), or MSREs (P = .42). The presence of PR interval prolongation or QRS width in this group did not predict MSREs (P = .22 and P = .96, respectively).


      In patients with syncope and bifascicular block, pacemaker implantation reduces adverse events as compared with ILR monitoring, irrespective of the type of BBB or the presence of PR interval prolongation.


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      Linked Article

      • Are bradyarrhythmias always the main cause of syncope in the elderly?
        Heart Rhythm
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          Managing patients with syncope is a major challenge for most cardiologists.1 This is mainly due to complexity and number of mechanisms that may cause or be associated with syncopal episodes. Whereas in young subjects syncope is often considered benign and a conservative approach is generally appropriate, its management becomes more complex and controversial in the elderly when a cardiac origin is documented or, often, suspected. In these patients, a syncopal episode may affect self-confidence in routine daily activities and increase concern for possible injuries related to falls and, in some cases, for death.
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