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Paroxysmal atrioventricular block: Electrophysiological mechanism of phase 4 conduction block in the His‐Purkinje system: A comparison with phase 3 block
Author(s) -
Shenasa Mohammad,
Josephson Mark E.,
Wit Andrew L.
Publication year - 2017
Publication title -
pacing and clinical electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.686
H-Index - 101
eISSN - 1540-8159
pISSN - 0147-8389
DOI - 10.1111/pace.13187
Subject(s) - medicine , cardiology , bradycardia , atrioventricular block , electrophysiology , syncope (phonology) , heart block , electrocardiography , asymptomatic , electrical conduction system of the heart , anesthesia , heart rate , blood pressure
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.