Key result
Exercise testing reveals irregular wide complex tachycardia with RBBB morphology, suggesting AF or left VT.
The differential diagnosis of exercise-induced irregular wide complex tachycardia with RBBB morphology includes AF with aberrancy/pre-excitation and specific left ventricular tachycardias.
Requires EP study to distinguish AF with aberrancy from LV tachycardia; hypothesis-generating for diagnostic criteria in exercise-induced irregular WCT with RBBB.
A 29-year-old active woman was referred for evaluation following the development of an irregular wide complex tachycardia with right bundle branch morphology and extreme QRS axis during exercise stress testing. Two main alternative diagnoses are discussed: a) atrial fibrillation with either aberrancy or pre-excitation; b) left ventricular tachycardia originating from the Purkinje system including left posterior fascicle versus posteromedial papillary muscle.
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Kalfon et al. (2026) studied this question. Exercise stress testing revealed irregular wide complex tachycardia with right bundle branch morphology, raising concerns for either atrial fibrillation or left ventricular tachycardia.
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