Heart 1999;81:73-81 ( January )
Electrophysiological determinant for induction of isthmus dependent counterclockwise and clockwise atrial flutter in humans
a Department
of Internal Medicine, National Taiwan University Hospital, 7 Chung-Shan South Road, Taipei 10018, Taiwan, b Department of Internal Medicine, National
Cheng-Kung University Hospital, Tainan, Taiwan
Correspondence to: Dr Huang.
Accepted for publication 10 July 1998
Objective
To
investigate the electrophysiological determinant underlying the
electrical induction of counterclockwise and clockwise isthmus
dependent atrial flutter.
Patients and
methodsThe isthmus bordered by the inferior vena
caval orifice-tricuspid annulus-coronary sinus ostium (IVCO-TA-CSO)
has been assumed to be the site of both slow conduction and
unidirectional block critical to the initiation of atrial flutter.
Trans-isthmus and the global atrial conduction were studied in 25 patients with isthmus dependent atrial flutter (group A) and in 21 patients without atrial flutter (group B), by pacing at the coronary
sinus ostium and the low lateral right atrium (LLRA) and mapping with a
20 pole Halo catheter in the right atrium.
ResultsMean
(SD) fluoroscopic isthmus length between the coronary sinus ostium and
LLRA sites was 28.1 (4.0) mm in group A and 28.0 (3.9) mm in group B
(p = 0.95), but the trans-isthmus conduction velocity of both
directions at various pacing cycle lengths was nearly halved in group A
compared with group B (mean 0.39-0.46 m/s v
0.83-0.89 m/s, p < 0.0001). Pacing at coronary sinus ostium directly induced counterclockwise atrial flutter in 14 patients and
pacing at LLRA induced clockwise atrial flutter in 11 patients, following abrupt unidirectional trans-isthmus block. Transient atrial
tachyarrhythmias preceded the onset of atrial flutter in 10 counterclockwise and six clockwise cases of atrial flutter. None of the
group B patients had inducible atrial flutter even in the presence of
trans-isthmus block. The intra- and interatrial conduction times, as
well as the conduction velocities at the right atrial free wall and the
septum, were similar and largely within the normal range in both groups.
ConclusionsCritical
slowing of the trans-IVCO
TACSO isthmus conduction, but not the
unidirectional block or the global atrial performance, is the
electrophysiological determinant of the induction of counterclockwise and clockwise isthmus dependent atrial flutter in man.
© 1999 by Heart
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This article has been cited by other articles:
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