RT-160
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Mechanism of induction of
typical atrial flutter by programmed stimulation
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Francisco G. Cosío, María
López-Gil*, Fernando Arribas*, Agustín Pastor, Ambrosio Núnez.
Cardiology Service, University Hospital of Getafe, Madrid,
*Arrhythmia Unit, University Hospital 12 de Octubre, Madrid, Spain
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Abstract
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Objective. Typical atrial flutter is
due to counterclockwise circular activation of the right atrium (RA), rotating around the
venae cavae and a line of block in the crista terminalis. We have studied mechanisms of
typical flutter induction by programmed stimulation with multiple recordings from the
septal and anterior RA.
Methods. We studied 12 patients (11 males) undergoing RF ablation
procedures for typical flutter. Stimulation was performed in the RA appendage, with 1-3
extrastimuli cycle lengths 600-250 ms, and finally burst. At least three simultaneous
recordings were obtained from 3 levels of the septal and anterior RA.
Results. Typical flutter was initiated by unidirectional block in the
low RA of activation descending the septum. It was preceded by atrial repetitive responses
in 12 cases, by a rapid atypical flutter in 1, and it started directly from the stimulated
front in 4.
Conclusions. Unidirectional block of repetitive responses on the
septal side of the CTI is the usual mechanism of typical flutter induction by programmed
stimulation in the RA appendage. This area of block may coincide with the proposed area of
slow conduction in the circuit.
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Key Words
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Catheter ablation of supraventricular
tachyarrhythmias
atrial flutter, counterclockwise circular activation, mechanisms of induction of AFl,
programmed stimulation, OA
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