Key result
Sinus tachycardia with 2:1 conduction can present with alternating narrow QRS and RBBB beats.
Why the study?
Regular alternation of wide and narrow QRS complexes is a rare electrocardiographic finding requiring further characterization.
Highlights a rare electrocardiographic finding of intermittent bundle branch block on alternate beats during sinus tachycardia.
Recognize alternating QRS in sinus tachycardia as possible 2:1 AV conduction; leaves open its prevalence and clinical significance.
Regular alternation of wide and narrow QRS complexes is a rare electrocardiographic finding. This report describes a case of sinus tachycardia with a 2:1 atrioventricular (A/V) conduction ratio, showing alternating narrow QRS complexes and right bundle branch block-patterned beats.
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Lin et al. (2026) studied this question. Sinus tachycardia with a 2:1 atrioventricular conduction ratio can present as a rare electrocardiographic pattern of alternating narrow QRS complexes and right bundle branch block beats.
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