Circulation, Vol 87, 1649-1660, Copyright © 1993 by American Heart Association
N Isber, M Restivo, WB Gough, H Yang and N el-Sherif
BACKGROUND. We have shown that atrial flutter (AF) in dogs with sterile
pericarditis is commonly due to a single-loop reentrant circuit in the
lower right atrium comprised of a functional or functional/anatomic
obstacle and a slow zone of conduction (SZ) between the central obstacle
and the atrioventricular (AV) ring. The goals of the present study were 1)
to establish that the epicardial SZ is the critical component of circus
movement AF and 2) to identify the optimal site within the epicardial SZ at
which interruption of circus movement can be accomplished by ablative
techniques. METHODS AND RESULTS. We analyzed the atrial activation patterns
during epicardial cooling of the SZ with as N2O-cooled probe in eight dogs
(five with clockwise [CW] reentrant circuit, one with counterclockwise
[CCW] reentrant circuit, and two with both CW and CCW reentrant circuits
around the same pathway). In all eight dogs, cooling (-5 to +5 degrees C
for 5-20 seconds) the narrow isthmus at the inferoposterior part of the SZ
between the central obstacle and the AV ring reversibly terminated the
reentrant circuit, whereas cooling outside this area failed to terminate
the reentrant circuit. The circus movement was not observed to continue
along alternate pathways when conduction in this critical zone was
interrupted. Both CW and CCW reentrant circuits could be terminated from
the same site within the SZ. Cooling resulted in slowing of conduction in
the SZ (55 +/- 15 msec) in both CW and CCW reentrant circuits.
Cooling-induced termination of CW reentrant circuits was characteristically
associated with oscillations of conduction in the cooled zone of the last
three cycles before termination and conduction block occurred within the
cooled zone. The last "manifest" reentrant cycle was associated with the
longest conduction delay in the cooled zone. However, this delay was not
necessarily reflected in the length of the last reentrant cycle because of
compensatory acceleration of conduction in the rest of the pathway. On the
other hand, in CCW reentrant circuits, conduction block occurred abruptly
at the distal border of the SZ and without significant oscillations of
conduction. CONCLUSIONS. The present study provides convincing evidence
that single-loop circus movement in this model is critically dependent on
an obligatory conduction in a SZ in the inferoposterior portion of the free
right atrial wall between a functional obstacle and the AV ring. Because
the atrial myocardium behaves electrophysiologically as a two-dimensional
surface, the results of this study may help to guide the endocardial
electrode catheter ablative technique for treatment of clinical AF.
ARTICLES
Circus movement atrial flutter in the canine sterile pericarditis model. Cryothermal termination from the epicardial site of the slow zone of the reentrant circuit
Department of Medicine, State University of New York, Health Science Center, Brooklyn 11203.
This article has been cited by other articles:
 |
|
 |
|
  M. D. Rodefeld, S. K. Gandhi, C. B. Huddleston, B. J. Turken, R. B. Schuessler, J. P. Boineau, J. L. Cox, and B. I. Bromberg ANATOMICALLY BASED ABLATION OF ATRIAL FLUTTER IN AN ACUTE CANINE MODEL OF THE MODIFIED FONTAN OPERATION J. Thorac. Cardiovasc. Surg., October 1, 1996; 112(4): 898 - 907. [Abstract] [Full Text]
|
|
|
|
 |
|
 F. Philippon, V. J. Plumb, A. E. Epstein, and G. N. Kay The Risk of Atrial Fibrillation Following Radiofrequency Catheter Ablation of Atrial Flutter Circulation, August 1, 1995; 92(3): 430 - 435. [Abstract] [Full Text]
|
|