Ct. Tai et al., ELECTROPHYSIOLOGIC CHARACTERISTICS AND RADIOFREQUENCY CATHETER ABLATION IN PATIENTS WITH CLOCKWISE ATRIAL-FLUTTER, Journal of cardiovascular electrophysiology, 8(1), 1997, pp. 24-34
RF Catheter Ablation of Clockwise Atrial Flutter, introduction: Althou
gh the mechanism and radiofrequency catheter ablation of counterclockw
ise (typical) atrial nutter have been studied extensively, information
about the electrocardiographic and electrophysiologic characteristics
and effects of radiofrequency ablation in patients with clockwise atr
ial Butter is limited, Methods and Results: Thirty consecutive patient
s with clinically documented paroxysmal clockwise atrial Butter were s
tudied, Endocardial recordings and entrainment study using a ''halo''
catheter with 10 electrode pairs in the right atrium were performed, R
adiofrequency energy was applied to the inferior vena cava-tricuspid a
nnulus (IVC-TA) and/or coronary sinus ostium-tricuspid annulus (CSO-TA
) isthmus to evaluate the effects of linear catheter ablation, Eightee
n patients had both counterclockwise and clockwise atrial Butters, and
12 patients had only clockwise atrial Butter, Both forms of atrial nu
tter had similar nutter cycle lengths (232 +/- 30 vs 226 +/- 25 msec,
P = 0.526) but reverse activation sequences, Right atrial pacing at a
cycle length 20 msec shorter than the nutter cycle length from the CSO
-TA isthmus, IVC-TA isthmus, and the area between the two isthmuses re
vealed concealed entrainment with stimulus-to-P wave intervals of 32 /- 19, 95 +/- 14, and 50 +/- 17 msec (P = 0.022) in the counterclockwi
se form, and 110 +/- 12, 40 +/- 20, and 60 +/- 15 msec (P = 0.018) in
the clockwise form. In clockwise atrial nutter 20 patients with biphas
ic P waves in the inferior leads had the presumed exit site of slow co
nduction area located at the low posterolateral right atrium; 10 patie
nts with positive P waves in the inferior leads had the presumed exit
site located at the mid-high posterolateral right atrium, Among the IS
patients with both forms of atrial nutter, linear ablation lesions di
rected at the IVC-TA isthmus eliminated both forms of atrial nutter in
14 patients; in the remaining 4 patients, CSO-TA linear lesions elimi
nated the counterclockwise form and IVC-TA lesions eliminated the cloc
kwise form. Among the 12 patients with the clockwise form only, CSO-TA
linear lesions eliminated nutter in 2 and IVC-TA linear lesions elimi
nated nutter in 10 patients. Successful ablation was confirmed by crea
tion of bidirectional conduction block in the IVC-TA and/or CSO-TA ist
hmus during pacing from the proximal coronary sinus and right posterol
ateral atrium sandwiching the linear lesions. During the follow-up per
iod of 17 +/- 8 months, 2 patients had recurrence of clockwise atrial
nutter, 1 patient had new onset of atypical atrial Butter, and 2 patie
nts had new onset of atrial fibrillation. Conclusions: Counterclockwis
e and clockwise atrial flutters may have overlapping slow conduction a
reas with different exit sites. Radiofrequency catheter ablation using
the linear method directed at the IVC-TA and CSO-TA isthmuses was fea
sible and effective in treating both forms of atrial nutter.