Dual conduction in a Mahaim fiber.
The case of an 8-year-old girl with incessant nonsustained left bundle branch block-like tachycardia refractory to antiarrhythmic drug therapy is reported. Electrophysiologic study revealed the presence of a right-sided accessory atriofascicular pathway. Episodes of nonsustained tachycardia were found to be based upon a dual response in AV conduction over the Mahaim fiber to one P wave. No reentrant tachycardia could be induced. The arrhythmia was cured by catheter ablation targeting a Mahaim potential at the right lateral tricuspid annulus. The findings can be explained by longitudinal dissociation in a single Mahaim fiber, a fiber distally diverging into two fibers with different conduction times, or (less likely) two closely located Mahaim fibers with different conduction times.
Department of Arrhythmia and Electrophysiology of BIOCOR Instituto, Nova Lima, Brazil. eduardosternick@aol.com
Eduardo Back
EB
Sternick
Eduardo A
EA
Sosa
Maurício I
MI
Scanavacca
Hein J J
HJ
Wellens
D002037:Bundle-Branch Block / Q000209:etiology; D002648:Child; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000002:abnormalities*; D006801:Humans; D013610:Tachycardia / Q000209:etiology*