Automaticity in Mahaim fibers.
BACKGROUND
Automatic rhythms associated with Mahaim fibers usually occur during radiofrequency catheter ablation. The incidence and significance of spontaneous automaticity in Mahaim fibers are unknown.


RESULTS
Spontaneous automatic rhythms were observed in 5 (12.5%) of 40 patients with Mahaim fibers referred for nonpharmacologic therapy because of recurrent episodes of symptomatic tachyarrhythmias, usually antidromic circus movement tachycardia (33/40 patients). Three were female and two were male. Their mean age was 15 +/- 7 years compared to 26 +/- 13 years of the patients without automaticity (P = 0.09). Three patients had both antidromic tachycardia and asymptomatic spontaneous automatic rhythms recorded during ambulatory ECG (1 patient) or electrophysiologic study (2 patients). In 2 patients, the automatic rhythm triggered antidromic tachycardia. Two other patients had nonsustained repetitive episodes of wide QRS tachycardia due to automaticity arising in the Mahaim fiber, without antidromic tachycardia. All automatic rhythms were abolished by successful catheter ablation of the Mahaim fibers.


CONCLUSIONS
Spontaneous automaticity occurred in 12.5% of our Mahaim patients and may trigger antidromic tachycardia. Spontaneous automaticity, which is not seen in rapidly conducting accessory pathways, is another argument for the presence of an AV nodal-like structure in Mahaim fibers.
Sternick
Eduardo Back
EB
Biocor Instituto, Belo Horizonte, Brazil. eduardosternick@aol.com
Sosa
Eduardo A
EA
Timmermans
Carl
C
Cruz Filho
Fernando E
FE
Rodriguez
Luz-Maria
LM
Gerken
Luiz M
LM
Scanavacca
Mauricio I
MI
Fagundes
Marcio L
ML
Bueno
Savia C
SC
Vrandecic
Mario O
MO
Wellens
Hein J J
HJ
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001283:Atrioventricular Node / Q000503:physiopathology; D017115:Catheter Ablation; D004562:Electrocardiography; D004594:Electrophysiology; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D011227:Pre-Excitation, Mahaim-Type / Q000503:physiopathology* / Q000601:surgery