Left atrial tachycardia originating from the mitral annulus-aorta junction.
BACKGROUND
At the mitral annulus-aorta (MA-Ao) junction, the left atrium is continuous through the subaortic curtain with the musculature of the anterior mitral leaflet. Under experimental conditions, this region can generate abnormal electrical activity. In patients with left atrial tachycardia, we investigated whether this region could be the source of this arrhythmia.


RESULTS
In 10 (28%) of 35 consecutive patients with left atrial tachycardia, the arrhythmia originated from the MA-Ao junction. Sustained, self-limited episodes of atrial tachycardia (cycle length, 340+/-56 ms; duration, 125+/-69 seconds) were repeatedly induced. Prematurity of the extrastimulus and time to first atrial tachycardia complex were directly correlated (R=0.66; P<0.001). During tachycardia, bipolar electrograms at the earliest site preceded onset of the P wave by 44+/-14 ms and were of longer duration and lower amplitude than those recorded from nearby left atrial sites (52+/-8 versus 24+/-4 ms, P<0.001; and 0.53+/-0.08 versus 3.45+/-0.96 mV, respectively; P<0.001). Ablation eliminated the tachycardia with no recurrence after a mean follow-up of 24+/-19 months. A comparative study in mouse embryos demonstrated the presence of the developing specialized conduction system in the MA-Ao region starting at embryonic age 11.5.


CONCLUSIONS
The MA-Ao junction can be a frequent source of left atrial tachycardia. This previously unrecognized site of origin may explain why catheter ablation has been less successful in eliminating left versus right atrial tachycardias. Remnants of the developing specialized conduction system could be the underlying substrate of this arrhythmia.
Gonzalez
Mario D
MD
Division of Cardiovascular Medicine, University of Florida College of Medicine, PO Box 100277, Gainesville, FL 32610-0277, USA. gonzamd@medicine.ufl.edu
Contreras
Leonardo J
LJ
Jongbloed
Monique R M
MR
Rivera
Jaime
J
Donahue
Timothy P
TP
Curtis
Anne B
AB
Bailey
Michael S
MS
Conti
Jamie B
JB
Fishman
Glenn I
GI
Schalij
Martin J
MJ
Gittenberger-de Groot
Adriana C
AC
D000318:Adrenergic beta-Agonists; D000328:Adult; D000628:Aminophylline; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use; D001011:Aorta / Q000503:physiopathology*; D017115:Catheter Ablation; D003131:Combined Modality Therapy; D004351:Drug Resistance; D005260:Female; D005318:Fetal Heart / Q000502:physiology; D005865:Gestational Age; D006325:Heart Atria / Q000503:physiopathology; D006329:Heart Conduction System / Q000196:embryology / Q000503:physiopathology*; D006801:Humans; D007545:Isoproterenol; D051379:Mice; D008875:Middle Aged; D008943:Mitral Valve / Q000503:physiopathology*; D013612:Tachycardia, Ectopic Atrial / Q000188:drug therapy / Q000503:physiopathology* / Q000601:surgery
D000318:Adrenergic beta-Agonists; D000889:Anti-Arrhythmia Agents; D000628:Aminophylline; D007545:Isoproterenol