Yonago Acta medica 2000;43:109–120

A Novel Technique for the Avoiding Catheter Dislodgment Caused by
Atrio-Ventricular Dissociation after Elimination of the Accessory
Pathway
Toshimitsu Suga, Osamu Igawa and Ichiro Hisatome
First Department of Internal Medicine, Faculty of Medicine, Tottori University, Yonago 6830826 Japan
We hypothesized that the atrio-ventricular (AV) dissociation occurring after eliminationof the accessory pathway conduction during right ventricular (RV) pacing made thestability of the ablation catheter worse. We confirmed this hypothesis by using a pacing
model. As a simulation model, sequential ventriculo-atrial (VA) pacing was designed
and studied in 20 patients without VA conduction. Prior to the sequential VA pacing,
3 catheters were positioned in the RV, right atrium (RA) and at the tricuspid valve
annulus (TVA), respectively. The sequential VA pacing consisted of continuous RV
pacing at a cycle length of 600 ms and RA pacing. The RA was paced at an interval of
125 ms following the RV pacing. To induce AV dissociation, RA pacing was abruptly
terminated during continuous sequential VA pacing. We observed the motion of thecatheter tip on the TVA before and after RA pacing using fluoroscopy in the 30˚ rightanterior oblique (RAO) and 45˚ left anterior oblique (LAO) views. The catheter tip
position in the end-systolic and end-diastolic phases was confirmed in each projection,and the distance of the catheter tip between these 2 phases was measured. The meanvalue of the catheter tip distance between the 2 phases obtained with sequential VA
pacing and fusion beats was 7.5 ± 3.2 and 21.0 ± 8.3 mm in the RAO (P < 0.001) and 8.0± 4.5 and 19.0 ± 8.6 mm in the LAO views (P < 0.001), respectively. Further, we proposeda new pacing maneuver to stabilize the ablation catheter position after the eliminationof accessory pathway conduction. Using sequential VA pacing, we examined catheter
tip movement during RF current delivery in 6 patients with the concealed WolffParkinson-White syndrome. During RF current delivery, catheter dislodgment did
not occur in any patients after the accessory pathway was eliminated when no fusion
beats occurred. In conclusion, AV dissociation occurring after elimination of theaccessory pathway conduction during RV pacing worsened the stability of the ablation
catheter. Furthermore, a new pacing maneuver during the RF application provided auseful method for maintaining stable catheter position for catheter ablation of accessory
pathways.
Key words: catheter dislodgment; sequential pacing; radiofrequency catheter ablation; WolffParkinson-White syndrome

In the case of manifest anterograde accessory
pathway conduction, radiofrequency (RF) energy is usually delivered during sinus rhythm tothe site with the shortest atrio-ventricular (AV)interval and/or an accessory pathway potential(Twidale et al., 1991; Calkins et al., 1992; Silkaet al., 1992; Bashir et al., 1993; Grimm et al.,1994). In the case of concealed retrograde accessory pathways, evaluation of the local electrogram is meaningful only during the retro-Abbreviations: AV, atrio-ventricular; CS, coronary sinus; HRA, high right atrium; LAO, left anterioroblique; RA, right atrium; RAO, right anterior oblique; RF, radiofrequency; RV, right ventricle/ventricular;
TVA, tricuspid valve annulus; VA, ventriculo-atrial; VCS, ventriculo-CS; VRA, ventriculo-HRA

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grade accessory pathway conduction occurring
during either orthodromic tachycardia or rightventricular (RV) pacing, and the RF energy isdelivered during either the tachycardia or RVpacing (Okumura et al., 1993; Li et al., 1994).
In all cases, during RF catheter ablation of accessory pathways, once the elimination of theaccessory pathway conduction is observed, theRF energy application should be continued for a
prolonged length of time in order to assure apermanent cure, even if there is a prompt loss of
the accessory pathway conduction within 2 to 3
s. Unfortunately, if the catheter movement occurs at the time of the elimination of the accessory pathway, in particular with concealed
retrograde accessory pathways in which it isnecessary to use RV pacing, the RF energy application cannot be continued and the temporary loss of accessory pathway conduction
can make subsequent mapping and ablation difficult. There have been many trials attempted
to avoid such an occurrence (Li et al., 1994;
Okumura et al., 1993); however, the cause ofthis accident has not yet been reported. In thisstudy, we hypothesized that the AV dissociation after the elimination of the accessory
pathway during RV pacing made the stability of
the ablation catheter worse. We confirmed thisby using a pacing model that simulated the condition when RF energy is delivered to the concealed accessory pathways during the constant
RV pacing. Further, we proposed new pacing
maneuvers, which we called sequential ventriculo-high right atrium (VRA) pacing or ventriculo-coronary sinus (VCS) pacing, to stabilize
the ablation catheter position after the elimination of the accessory pathway. Therefore, wewould like to describe our preliminary experience with this technique.

Patients and Methods

Pacing model
Sequential ventriculo-atrial (VA) pacing wasdesigned as a model to simulate the condition
when RF energy is delivered to concealed accessory pathways during constant RV pacing.

The study population consisted of 20 consecutive patients (12 males, 8 females; mean age, 42± 24 years) who underwent electrophysiological examination between July1996 andSeptember 1997 in the Division of Cardiology,First Department of Internal Medicine, Facultyof Medicine, Tottori University. Out of the 20patients, 7 had the sick sinus syndrome and 13
were successfully ablated Wolff-ParkinsonWhite syndrome patients. In this examination,
we confirmed that no patients had VA conduction or structural heart disease. Antiarrhythmic
drugs were discontinued for at least a 5-foldperiod of their half-life in all patients. The research was performed after completion of thediagnostic study in the sick sinus syndrome
patients and after successful ablation in theWolff-Parkinson-White patients.
Prior to the sequential VA pacing, two 5-Fr
quadripolar (5 mm interelectrode spacing) catheters (Cordis Webster, Baldwin Park, CA) wereintroduced via the inferior vena cava and positioned in the right atrium (RA) and RV. A 7-Fr
quadripolar catheter with a large tip electrode(electrode length 4 mm; Cordis Webster) wasintroduced via the inferior vena cava and positioned on the tricuspid valve annulus (TVA).
One indicator that the catheter on the TVA,
which represented the RF catheter, was satisfactorily positioned, was the presence of clearand discernible equal atrial and ventricularcomponents of the local electrogram recordedfrom the distal pair of electrodes of the catheter.
Simultaneously performed right coronary artery
angiography supported the existence of satisfactory positioning. The sequential VA pacing
consisted of continuous RV pacing at a cycle
length of 600 ms and RA pacing. The RA waspaced at an interval of 125 ms following the RV
pacing. Both pacing impulses constantly collided in the normal conduction system (Fig. 1 A).
RV pacing was obtained by abrupt terminationof the RA pacing during continuous sequential
VA pacing. The sinus node function recovered
due to the termination of the RA pacing. The
different rates of the sinus rhythm and RV pacing prevented constant collision of the impulses(Fig. 1B). In this manner, we were able to simulate the same condition as that observed during110

A technique for avoiding catheter dislodgment

AB

RA pacing

SA nodeSinus node function
recoveryRA
AV nodeAV nodeTVATVA*
RV pacing

RV pacing

Sequential VApacing

Sinus node(ms)RVpacing

Sinus nodeRARA

AV nodeAV nodeRV(ms)

RV600600600600

125600600125

Fig. 1. Illustrations showing the method of sequential ventriculo-atrial (VA) and right ventricular (RV)
pacings, with the conduction patterns during sequential VA pacing (A) and during RV pacing (B). See thetext for details. AV, atrio-ventricular; SA, sinoatrial; RA, right atrium; TVA, tricuspid valve annulus.

elimination of accessory pathways. In otherwords, sequential VA pacing was the condition
before the elimination of accessory pathway,
and sequential RV pacing, after the elimination.
During sequential VA or RV pacing, the movement of the catheter tip on the TVA, was observed using fluoroscopy in the 30˚ right anterior oblique (RAO) and 45˚ left anterior oblique(LAO) views. The position of this catheter tip
during the end-systolic and end-diastolic phases
was confirmed in each projection, and the distance between the position of the catheter tip inthese 2 phases was measured. Body surface andintracardiac electrograms were monitored andrecorded with an EP Amp and EP Lab (Quinton,Seattle, WA). Pacing was performed with acardiac stimulator (SEC-3102, Nihon Kohden,Tokyo, Japan) using rectangular stimuli at
twice the diastolic threshold and a pulse widthof 2 ms. The distal pair of electrodes of RV andRA were used for stimulation, while the proximal pair of electrodes were used for recording
the local bipolar electrogram.

RF ablation under sequential VRA orVCS pacing
The pacing technique was used in 6 patients inwhom either right or left concealed accessory
pathways was electrophysiologically diagnosed. Out of the 6 patients (4 males, 2 females;mean age, 42 ± 24 years), 4 patients had leftsided and 2 right-sided accessory pathways.
Using this sequential VA pacing, we were able
to design a method that would mimic the VA
conduction, that occurs with accessory pathways
during RV pacing, even after the elimination of
the accessory pathway conduction. When theaccessory pathway was located on the left side,
RF ablation was performed using an RF generator(CAT 500, Central Inc., Ichikawa, Japan) while
delivering sequential VRA pacing. The RVhigh RA (HRA) pacing interval was programmed to be the maximum interval in which theatrial wave front propagating from the HRA
pacing site did not hide the earliest activation ofthe left atrium through the accessory pathway.

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ABefore

BSA node

SA nodeCS pacingRA pacing
AV nodeAV nodeAccessorypathway

RV pacing
RV pacing

SA nodeSA nodeAfterCS pacing

RA pacing
AV nodeAV nodeRV pacing
RV pacingFig. 2. Illustration showing the activation sequences before and after the elimination of accessory pathway
conduction when sequential ventriculo-high right atrium pacing (A) or ventriculo-coronary sinus (CS) pacing(B) is applied during the radiofrequency application. A: A left-sided accessory pathway case. B: A rightsided accessory pathway case. See the text for details. AV, atrio-ventricular; RA, right atrium; RV, rightventricular; SA, sinoatrial.

In other words, the VA interval was programmed in order to minimize the atrial activation through the accessory pathway to justonly local activation (minimum atrial activation) (Fig. 2A). If the accessory pathway waslocated on the right side, we performed RF
ablation during sequential VCS pacing (Fig.
2B). If elimination of the accessory pathway
conduction was observed, the RF energy application was continued for 60 s at 20 W. Before
and after elimination of the accessory pathway,
the movement of the ablation catheter tip on themitral or tricuspid valve annulus, was observed
using fluoroscopy in the 30˚ RAO and 45˚ LAOviews. The position of this catheter tip during

the end-systolic and end-diastolic phases wasconfirmed in each projection, and the distance
between the position of the catheter tip in these2 phases was measured over 5 consecutive
beats. All patients gave written informed consent to participate in this study.

Data and Statistical AnalysisAll data were presented as mean ± SD. Continuous variables were compared using Student’s t-test for paired samples. A probabilityof < 0.05 was considered statistically significant.

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A technique for avoiding catheter dislodgment

and LAO projections, respectively. As a result, the distancesABobserved with the fusion beats
were substantially longer than
21.0±8.3
19.0±8.6
NSNS2020
those during sequential VA
7.9±3.1
8.7±3.8
pacing (P < 0.001) (Fig. 3B). In10106 patients the local electrogram
recorded from the distal pair of
7.5±3.2
7.5±3.2
8.0±4.5
8.0±4.5
electrodes of the TVA catheter
00RAO
LAORAOLAOduring fusion beats with RVnpacing varied from that duringn
AP RVP VAP RVPAP sio tAP ioSVSSV Fubea SV Fubseat
sequential VA pacing.
Typical examples of TVAFig. 3. The distance between the location of the catheter tip on thetricuspid valve annulus in the end-systolic and end-diastolic
motion during sequential VA
phases. A shows mean values of the distance during sequential VA
pacing and a fusion beat arepacing (SVAP) and RV pacing (RVP), not including fusion beats.
shown in Figs. 4 and 5. In Fig.
B shows mean values of the distance during SVAP and fusion
4, RA pacing at an interval ofbeats. LAO, 45˚ left anterior oblique view; NS, not significant;
125 ms following the RV
RAO, 30˚ right anterior oblique view.
pacing was discontinued abruptly during constant RV
pacing at a cycle length of 600
ms. This indicated that a fusion beat resulting
Results
from a sinus beat propagating down the normal
AV conduction system occurred when the sinusSequential VA pacing
node function had recovered after stopping theThe catheter located on the TVA was position- RA pacing (see the asterisk). The local eleced on the right posterior-lateral TVA in all pa- trogram recorded from the distal pair of electients. The catheter tip movement revealed that trodes of the TVA catheter altered with the futhe TVA motion was weak and constant during sion beats. Depicted in Fig. 5 is the fluoroscopy
sequential VA pacing, and had a tendency to be taken during right coronary artery angiogram instrong during RV pacing regardless of patients the 30˚ RAO and 45˚ LAO views during serespirations. The mean value of the distance quential VA pacing (Fig. 5A) and RV pacingthat the catheter tip moved from its position in when a fusion beat occurred (Fig. 5B). The 2
the end-systolic phase to that in the end-diastol- images of the end-systolic and end-diastolic
ic phase during sequential VA or RV pacing, phases were superimposed during each pacing
except during fusion beats, for 10 beats was 7.5 attempt. The distance of the catheter tip± 3.2 mm and 7.9 ± 3.1 mm in the RAO projec- movement on the TVA was measured. Thetion and 8.0 ± 4.5 mm and 8.7 ± 3.8 mm in the distance of the catheter tip movement during
LAO projection, respectively. However, there sequential VA pacing was 4.9 mm and 4.2 mm
was no significant difference between the val- in the RAO and LAO projections, respectively
ues obtained during sequential VA or RV (Fig. 5A). On the other hand, the distancepacing in either projection (Fig. 3A). However, during a fusion beat was 16.7 mm and 13.9 mm
when a fusion beat during RV pacing resulting in the RAO and LAO projections, respectively
from a supraventricular beat propagating down (Fig. 5B). This indicated that the distance of thethe normal AV conduction system occurred, catheter tip moved during the fusion beat wasthere was strong and abrupt movement of the longer than that during sequential VA pacing.
TVA catheter. The mean value of the distance The above results indicate that fusion beat will
the catheter moved during the fusion beats was play the pivotal role for the dislodgment of ca21.0 ± 8.3 mm and 19.0 ± 8.6 mm in the RAO theter tip.
(mm)
30(mm)
30

P < 0.001

P < 0.001

113