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Cause of Recurrent Syncope in an Elderly Patient

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A man in his 80s with recurrent syncope was admitted to the emergency department. The patient previously underwent an electrophysiological study (the exact procedure was unknown) in another hospital because of syncope, and the result did not suggest the need for pacemaker implantation. He denied a recent medical history of chest pain or dyspnea on exertion. On examination, his oxygen saturation while breathing room air was 98%, and his blood pressure was 120/76 mm Hg. The result of cardiopulmonary examination was unremarkable. Echocardiogram findings revealed a left ventricular ejection fraction of 54% with normal ventricular wall motion. Blood laboratory data, including serial high-sensitivity troponin, D-dimer, renal function, electrolytes, and blood glucose, were unremarkable. The results of the electrocardiogram (ECG) that was performed at admission was recorded (Figure, A).

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Bifascicular block is a conduction disorder that has a reported prevalence of 1% to 1.5%, including complete left bundle branch block or RBBB with either LAFB or left posterior fascicular block.1 Bifasicular block may be accompanied by residual functional bundle lesions, and there is a risk of progression to complete AV block.2 In this case, the elderly patient's baseline ECG showed bifascicular block (RBBB and LAFB) and left posterior fascicle (the residual) working (was functional). The incidence of bifascicular block progressing to complete AV block is 1% to 6% each year.3 A study4 showed that 10% to 15% of patients with bifasicular block may experience syncope within 3 years. The potential causes of syncope are heterogeneous, but intermittent complete AV block is a frequent cause.1,5 In this case, complete AV block was recorded when the elderly patient with bifasicular block experienced syncope again in the emergency department. The patient did not develop any episodes of syncope after dual-chamber pacemaker implantation, confirming that syncope was associated with intermittent complete AV block.

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Article Information

Corresponding Author: Hao-Yu Wu, MD, PhD, Department of Cardiology, Shaanxi Provincial People's Hospital, No. 256 West Youyi Rd, Shaanxi Province, Xi'an 710068, China (wxs5132006@163.com).

Published Online: June 13, 2022. doi:10.1001/jamainternmed.2022.2016

Conflict of Interest Disclosures: None reported.

References
1.
Brignole  M , Menozzi  C , Moya  A ,  et al; International Study on Syncope of Uncertain Etiology (ISSUE) Investigators.  Mechanism of syncope in patients with bundle branch block and negative electrophysiological test.   Circulation. 2001;104(17):2045-2050. doi:10.1161/hc4201.097837PubMedGoogle ScholarCrossref
2.
McAnulty  JH , Rahimtoola  SH , Murphy  E ,  et al.  Natural history of “high-risk” bundle-branch block: final report of a prospective study.   N Engl J Med. 1982;307(3):137-143. doi:10.1056/NEJM198207153070301PubMedGoogle ScholarCrossref
3.
Moulki  N , Kealhofer  JV , Benditt  DG ,  et al.  Association of cardiac implantable electronic devices with survival in bifascicular block and prolonged PR interval on electrocardiogram.   J Interv Card Electrophysiol. 2018;52(3):335-341. doi:10.1007/s10840-018-0389-0PubMedGoogle ScholarCrossref
4.
Englund  A , Bergfeldt  L , Rehnqvist  N , Aström  H , Rosenqvist  M .  Diagnostic value of programmed ventricular stimulation in patients with bifascicular block: a prospective study of patients with and without syncope.   J Am Coll Cardiol. 1995;26(6):1508-1515. doi:10.1016/0735-1097(95)00354-1PubMedGoogle ScholarCrossref
5.
Brignole  M , Sutton  R , Menozzi  C ,  et al; International Study on Syncope of Uncertain Etiology 2 (ISSUE 2) Group.  Early application of an implantable loop recorder allows effective specific therapy in patients with recurrent suspected neurally mediated syncope.   Eur Heart J. 2006;27(9):1085-1092. doi:10.1093/eurheartj/ehi842PubMedGoogle ScholarCrossref
6.
Glikson  M , Nielsen  JC , Kronborg  MB ,  et al; ESC Scientific Document Group.  2021 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy.   Eur Heart J. 2021;42(35):3427-3520. doi:10.1093/eurheartj/ehab364PubMedGoogle ScholarCrossref
7.
Santini  M , Castro  A , Giada  F ,  et al.  Prevention of syncope through permanent cardiac pacing in patients with bifascicular block and syncope of unexplained origin: the PRESS study.   Circ Arrhythm Electrophysiol. 2013;6(1):101-107. doi:10.1161/CIRCEP.112.975102PubMedGoogle ScholarCrossref
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