This document describes the technique of radiofrequency ablation for atrioventricular nodal reentrant tachycardia (AVNRT). It discusses catheter positioning between the coronary sinus os and tricuspid valve for ablation. The areas targeted for slow and fast pathway ablation are shown. Progression of ablation sites from the coronary sinus os inferiorly and superiorly on the septum are presented. Acceptable ablation areas between the His catheter and roof of the coronary sinus are outlined to minimize heart block risks. A case of successful AVNRT ablation in a 73-year old woman is then presented, demonstrating induction of the arrhythmia and pace mapping to identify the slow pathway for ablation.

1. Technique of Ablation of
AVNRT
And case presentation
Prof. Samir Rafla, FACC, FESC
Alexandria Univ.

2. Catheter position for radiofrequency slow pathway ablation. The
tip of the ablation catheter is between the coronary sinus (CS) os
and the tricuspid valve in the right anterior oblique (RAO) view. In
the left anterior oblique (LAO) view, the tip of the ablation catheter
is just posterior (septal) to the His catheter at the level of the
coronary sinus os. Note the angled sheath supporting the ablation
catheter.

3. A, Right anterior oblique (RAO) view of the cardiac anatomy
surrounding the triangle of Koch (upper left) and catheter positions
for ablation of the slow pathway as shown in (upper right).

4. Annotated versions of the upper figures. In the lower right, the catheter
positions are superimposed on the cardiac anatomy, showing the
ablation catheter tip for slow pathway ablation in the area between the
coronary sinus (CS) os and the tricuspid valve (TV).

5. The areas for slow and fast pathway ablation are shaded in
red. In the lower right panel, the salient cardiac anatomic
features are superimposed on the RAO fluoroscopic view of
the catheter positions.

7. Progression of ablation sites (shaded yellow areas) for slow pathway ablation.
Left panels show RAO views, right panels show LAO views. 1. The first ablation
attempts are directed at the area between the coronary sinus (CS) os (dashed
circle) and the tricuspid valve no more superiorly than the roof of the CS. 2. The
second area for ablation is between the CS and tricuspid valve (TV) but inferior
to the CS os. 3. The third area is the proximal CS. 4. The last area for ablation
is more superiorly on the septum above the level of the CS os. The risk for
atrioventricular block is increased with ablation superior to the CS os.

9. Limits of anatomic sites for slow pathway ablation. A, In the left anterior oblique (LAO)
view, acceptable areas for ablation are slightly septal to the His catheter and generally
between 3 and 6 o'clock, with the His catheter representing 12 o'clock and the roof of the
CS 6 o'clock. B, Right anterior oblique view of ablation catheter (AB) at the level of the
coronary sinus (CS) os near the tricuspid annulus. The estimated boundaries of the
triangle of Koch are delineated by the broken lines. The green marker indicates the
caudal to cranial limits with the lowest incidence of heart block. This area corresponds to
sites inferior to the CS os to the superior margin (roof ) of the CS os. The area in red,
beginning near the mid-point between the CS os and the His recording, represents a
high risk for atrioventricular block. The area in yellow, beginning at the roof of the CS, is
intermediate risk for heart block.

10. Case : Case Summary
The patient is a 73-year-old female with
a long history of palpitations and
hypertension. Echo reveals normal
LVEF with an LA diameter of 38 mm.
The transesophageal EP
study revealed SVT, which was induced
with minimum effort .

11. Fig. 1.1 The 12-lead resting ECG (paper speed 25 mm/s)
showed sinus rhythm with a ventricular rate of 80 bpm a
short PR interval (102 ms) and a QRS width of 80 ms

12. Fig. 1.2

13. Case Discussion
Although the patient is elderly, the ECG
shows a regular narrow complex
tachycardia. Atrial tachycardia, AVNRT,
and AVRT should all be considered. In
this case, no visible P waves are seen
during the SVT. This suggests either
AVNRT or AT with a long PR interval. In
this case, AVNRT was induced in the EP
lab and successfully ablated (Figs. 1.3–
1.16).

14. Fig. 1.3 Intracardiac recordings taken at baseline during the
electrophysiology study (paper speed 200 mm/s). Four surface ECG leads (I,
aVF, V1, V6), one bipolar recording from the high right atrium (HRA), three
bipolar recordings from the His bundle region (distal = HIS D, intermediate =
HIS I and proximal = HIS P), two bipolar recordings from the coronary sinus
(CS prox =proximal coronary sinus and CS dist = distal coronary sinus), and
the distal bipolar recording of the mapping catheter (MC D). A atrium, V
ventricle, H His bundle

15. Fig. 1.4 (a, b). Intracardiac recordings taken during programmed atrial stimulation
(paper speed 200 mm/s). Same display that is shown in Fig. 1.3. (a) With a coupling
interval of 410 ms the AH interval is 188 ms and (b) with a coupling interval of 280
ms it suddenly increased to 307 ms (ERP of the fast pathway with a jump of 120 ms)
a

16. Fig. 1.5 Intracardiac recordings taken during programmed atrial stimulation
with two beats with retrograde conduction through the fast pathway (S slow
pathway and F fast pathway) (paper speed 100 mm/s). Same display as that
shown in Fig. 1.3

17. Fig. 1.8 Intracardiac recordings taken during programmed atrial stimulation with an
infusion of isoproterenol IV (paper speed 100 mm/s) showing induction of AVNRT (cycle
length 300 ms).

18. Fig. 1.9 Intracardiac recordings (paper speed 200 mm/s). Same display as shown in
Fig. 1.3. Pace mapping of the anteroseptal region of Koch’s triangle with a stim-H
interval of 78 ms. St pacing, A atrium, V ventricle, H His bundle

19. Fig. 18.10 Intracardiac recordings (paper speed 200 mm/s). Same display as
Fig. 1.19-3. Pace mapping of the midseptal region of Koch’s triangle with a stim-H
interval of 81 ms. St pacing, A atrium, V ventricle, H His bundle

20. Fig. 1.11 Intracardiac recordings (paper speed 200 mm/s). Same display as shown in
Fig. 1.3. Pace mapping of the posteroseptal region of Koch’s triangle with a stim-H
interval of 106 ms. St pacing, A atrium, V ventricle, H His bundle

21. Fig. 1.12 Intracardiac recordings (paper speed 200 mm/s). Same display as
shown in Fig. 1.3. Ablation site slow pathway potential

22. Fig. 1.16 RAO and LAO of mapping catheter at the
ablation site in the posteroseptal part of Koch’s triangle
Delise P, Sitta N, Bonso A, et al. Pace mapping of Koch’s triangle reduces risk of
atrioventricular block during ablation of atrioventricular nodal reentrant tachycardia. J
Cardiovasc Electrophysiol. 2005;16:30-35.

23. Source of slides of technique:
CATHETER ABLATION OF CARDIAC ARRHYTHMIAS
Edited by Shoei K. Stephen Huang and Mark A. Wood. –
2nd Ed. Copyright © 2011, 2006 by Saunders, an imprint
of Elsevier Inc.
Source of slides of case:
Cardiac Electrophysiology Clinical Case Review
Andrea Natale • Amin Al-Ahmad, Paul J. Wang • John
P. DiMarco. (Editors) © Springer-Verlag London Limited
2011