Mechanism of adenosine-induced termination of focal atrial tachycardia.
BACKGROUND
Adenosine can terminate most focal atrial tachycardias (ATs). However, information about the termination mechanism is limited. This study investigated the effects and mechanism of adenosine on terminating focal AT using a three-dimensional noncontact mapping system.


RESULTS
The study consisted of 7 patients (4 men and 3 women; age 44 +/- 29 years) with focal AT. Cycle length variation and atrial activation pattern at baseline and just before AT termination by adenosine (3-12 mg) were analyzed. Noncontact mapping demonstrated focal AT propagated from the origin (O) with preferential conduction and spread away from the breakout sites to the whole atrium. Compared to baseline AT, termination episodes revealed higher mean beat-to-beat variation of AT cycle length (11.7 +/- 11.7 msec vs 4.7 +/- 4.5 msec, P < 0.001) and standard deviation of normalized AT cycle length (0.033 +/- 0.014 vs 0.011 +/- 0.005, P < 0.001). In termination episodes, adenosine significantly decreased the peak negative voltage of AT-O (-27.2 +/- 15.3%, P < 0.01), preferential conduction (proximal: -32.1 +/- 18.7, mid: -28.4 +/- 22.8, distal portion: -29.6 +/- 21.4%, P < 0.01), and breakout (-31.4 +/- 12.5%, P < 0.01). However, adenosine did not affect voltage in nontermination episodes. Adenosine shifted the locations of AT-O in 5 of 10 AT episodes with termination. Mean number of shifting AT-O was 2.4 +/- 1.5 (range 1-4), with maximum shifting distance of 15.0 +/- 3.1 (range 10-19) mm. Focal activation at AT-O simply disappeared in all termination episodes and therefore was not due to conduction block within preferential conduction or breakout site. Catheter ablation lesions covered 50% of total shifting origins, without late recurrence.


CONCLUSIONS
Adenosine-induced AT termination was associated with significantly decreased electrogram voltage, shifting AT-O locations, and disappearance of focal activation.
Higa
Satoshi
S
Division of Cardiology, Department of Medicine, National Yang-Ming University School of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan.
Tai
Ching-Tai
CT
Lin
Yenn-Jiang
YJ
Liu
Tu-Ying
TY
Lee
Pi-Chang
PC
Huang
Jin-Long
JL
Yuniadi
Yoga
Y
Huang
Bien-Hsien
BH
Hsieh
Ming-Hsiung
MH
Lee
Shih-Huang
SH
Kuo
Jen-Yuan
JY
Lee
Kun-Tai
KT
Chen
Shih-Ann
SA
D000241:Adenosine / Q000627:therapeutic use*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use*; D017115:Catheter Ablation; D004562:Electrocardiography; D005260:Female; D006801:Humans; D007267:Injections; D008297:Male; D008875:Middle Aged; D018709:Statistics, Nonparametric; D013617:Tachycardia, Supraventricular / Q000188:drug therapy* / Q000601:surgery; D016896:Treatment Outcome
D000889:Anti-Arrhythmia Agents; D000241:Adenosine