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Sequential Electrocardiographic Progression of Alternating Bundle Branch Block Culminating in Complete
Ashley S Goodwin1, Jose Roberto Martinez-Parachini1, Marc C Engels1
1Department of Medicine, Division of Cardiology, University of Utah, Salt Lake City, Utah, USA.
Background:
Alternating bundle branch block (ABBB) is defined by a transient spontaneous block in the right and left bundles (including left anterior or posterior fascicles) diagnosed on consecutive electrocardiogram (ECG) tracings.
Case Summary:
A 74-year-old man with hypertension and a remote inferior myocardial infarction presented with fatigue and syncope. Initial ECG showed sinus rhythm with a first-degree atrioventricular block and ABBB. During hospital admission, he experienced syncope, and a subsequent ECG showed an unstable complete heart block. He was resuscitated with emergent transcutaneous pacing and underwent permanent pacemaker implantation.
Discussion:
This case captures a rare ECG demonstrating sequential ABBB, a harbinger for rapid progression to a high-degree atrioventricular block. According to American College of Cardiology/American Heart Association/Heart Rhythm Society and European Society of Cardiology Guidelines, pacing is a class 1 indication for ABBB with or without symptoms. Early recognition is essential for timely pacemaker implantation.
Take-Home Messages:
ABBB represents significant infra-Hisian conduction disease with an increased risk for progression to a high-degree block. ABBB is a class 1 indication for pacemaker implantation.
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