Paroxysmal atrioventricular block: Electrophysiological mechanism of phase 4 conduction block in the His‐Purkinje system: A comparison with phase 3 block

Background Paroxysmal atrioventricular (A‐V) block is relatively rare, and due to its transient nature, it is often under recognized. It is often triggered by atrial, junctional, or ventricular premature beats, and occurs in the presence of a diseased His‐Purkinje system (HPS). Here, we present a 45...

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Bibliographic Details
Published in:Pacing and clinical electrophysiology 2017-11, Vol.40 (11), p.1234-1241
Main Authors: Shenasa, Mohammad, Josephson, Mark E., Wit, Andrew L.
Format: Article
Language:English
Subjects:
Atrioventricular Block - diagnosis
Atrioventricular Block - physiopathology
Bradycardia
Bundle of His - physiopathology
Cardiac arrhythmia
Depolarization
Diagnosis, Differential
Differential diagnosis
Electrocardiography
Heart
Heart diseases
His‐Purkinje system
Humans
Male
Middle Aged
paroxysmal A‐V block
phase 3 A‐V block
phase 4 A‐V block
Purkinje Fibers - physiopathology
Syncope
Ventricle
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Summary:Background Paroxysmal atrioventricular (A‐V) block is relatively rare, and due to its transient nature, it is often under recognized. It is often triggered by atrial, junctional, or ventricular premature beats, and occurs in the presence of a diseased His‐Purkinje system (HPS). Here, we present a 45‐year‐old white male who was admitted for observation due to recurrent syncope and near‐syncope, who had paroxysmal A‐V block. The likely cellular electrophysiological mechanisms(s) of paroxysmal A‐V block and its differential diagnosis and management are discussed. Methods Continuous electrocardiographic monitoring was done while the patient was in the cardiac unit. Results Multiple episodes of paroxysmal A‐V block were documented in this case. All episodes were initiated and terminated with atrial/junctional premature beats. The patient underwent permanent pacemaker implantation and has remained asymptomatic since then. Conclusions Paroxysmal A‐V block is rare and often causes syncope or near‐syncope. Permanent pacemaker implantation is indicated according to the current guidelines. Paroxysmal A‐V block occurs in the setting of diseased HPS and is bradycardia‐dependent. The detailed electrophysiological mechanisms, which involve phase 4 diastolic depolarization, and differential diagnosis are discussed.
ISSN:0147-8389
1540-8159
DOI:10.1111/pace.13187