Luc De Roy, MD is the Professor of Cardiology Université de Louvain, Cliniques Universitaires UCL de Mont Godinne, Belgium. During his many years of practice, he has developed his approach to the treatment of atrial flutter (AFL) by utilizing specific tools and protocols. The benefits of his techniques have been to reduce procedure and fluoroscopy times, as well as minimizing the number of radiofrequency (RF) applications needed to obtain successful therapy for his patients. Prof. De Roy shares the details of his approach, and some of the variations seen, in a discussion of a case report of cavo-tricuspid isthmus (CTI) dependent AFL.

Patient History
       The patient was a 70-year-old female who presented with a history of recurrent paroxysmal AFL. Echocardiogram demonstrated a normal heart; electrocardiogram (ECG) showed a typical atrial flutter characterized by a dominant negative F wave morphology in the inferior leads, II, III and aVF (Figure 1A).
       After failing anti-arrhythmic therapy, the patient was admitted for a diagnostic EP procedure and therapeutic catheter ablation of her arrhythmia.

Electrophysiologic Procedure
       Vascular access was obtained via the right femoral vein. For the initial diagnosis, a Livewire™ Duo-Decapolar catheter was inserted into the right atrium (RA), and the 20 electrodes, connected in pairs, were positioned around the tricuspid annular side of the crista terminalis (Figure 2). The Duo-Decapolar catheter was positioned to provide mapping from the distal electrode pair (D1) at the medial aspect of the CTI, through the isthmus, lateral wall, the superior right atrium and around to the proximal electrode pair (D10) on the high septum. Observation of the electrograms during tachycardia demonstrated a continuous pattern of activation with a counter-clockwise rotation consistent with CTI-dependent AFL (Figure 1B). The isthmus dependency of this arrhythmia was confirmed by the technique of concealed entrainment.

Figure 2.

Biplane view in a 30° right anterior oblique (RAO) and 40° left anterior oblique (LAO) projection. Catheter positioning before ablation. A duo-decapolar catheter (D) is placed on the lateral wall of the RA, the distal part of it facing the lower septum. A Livewire™ Decapolar (LD) catheter has been introduced in the CS for pacing and recording of the EGMs of the septal part of the isthmus. A RAMP-1™ guiding introducer has been placed on the isthmus, oriented perpendicularly to the plane of the LAO 40° projection. A Livewire™ TC ablation catheter (ABL) has been advanced through the introducer in order to position its tip on the CTI.

Therapeutic procedure
       In order to visualize the anatomy of the isthmus, which often has a slight, or even pronounced, concave pattern with a sometimes marked irregular base and varying length, we performed an angiogram of the RA. This was done with injection of 40 ml of contrast medium through the RAMP-1™ 8 French guiding introducer, placed at the junction of the inferior vena cava (IVC) and RA (Figure 3).
       The next step consisted of pulling the distal end of the Livewire™ Duo-Decapolar catheter out of the way, over to the lower lateral part of the RA wall, which allowed free access of the ablation catheter to the CTI ablation target (Figure 4). The RAMP-1 introducer was placed to the level of the isthmus and the ablation catheter was advanced through it in order to stabilize the catheter on the ventricular aspect of the isthmus. The ideal position is one where the distal bipole of the catheter records a distinct ventricular “V” wave of sufficient amplitude and a minimal amplitude of atrial “A” waves.

Figure 3.

RAO 30° and LAO 40° views during contrast injection of 40 ml through the RAMP-1™ introducer at the junction of the inferior vena cava (IVC) and RA, showing the RA and CTI which has here a flat horizontal course and a length of 30 mm. The tricuspid valve (TV) limit is clearly seen as well as a part of the right ventricle (RV) and pulmonary artery (PA). The TV is nicely visualized in the RAO projection, separating the RA from the RV. A decapolar catheter has been inserted into the CS as a landmark for pacing and recording from the CS os. D = Livewire™ Duo-Decapolar catheter; LD = Livewire™ Decapolar catheter; R = RAMP-1TM Introducer.

       Ablation may be performed during AFL or in sinus rhythm. Sequential burns are delivered from the distal ventricular part of the isthmus, dragging the ablation catheter progressively towards the IVC. Interruption of the AFL during ablation confirms the isthmus dependency of the arrhythmia, but the cyclic rapid movement of the isthmus during AFL may render ablation less effective due to smaller and incomplete lesions. These movements from the atrium and the rapid ventricular rate may actually prevent an optimal tip-tissue contact on the isthmus. This may result in superficial lesions with subsequent edema, prohibiting further complete isthmus interruption despite an initial termination of the AFL. In this specific situation, the RAMP-1™ introducer appears to be an important tool to obtain an optimal contact of the catheter on the isthmus, even during tachycardia.

Figure 4.

Same abbreviations as in previous figures. The duo-decapolar catheter is now partially withdrawn to enable free access to the isthmus. The distal tip of the catheter is positioned at the low lateral part of the RA. The RAMP-1™ introducer is placed on the isthmus, perpendicular to the LAO 40° plane, allowing the ablation catheter to be positioned on the ventricular part of the isthmus.

       When the AFL has been interrupted (Figures 5–6) and/or when ablation is attempted during sinus rhythm, we pace the low atrial septum. This can be achieved by stimulation from the proximal poles of the decapolar catheter which has been inserted within the CS to allow a stable and constant stimulation position.

Figure 5.

Same abbreviations as in previous figures. Interruption of the AFL during ablation. The atrial wavefront (fifth from the left), descending the lateral atrial wall becomes blocked at the isthmus level after a slight progressive slowing, precluding depolarization of the lower septum. Likewise, in the CS, the atrial deflection disappears at the precise moment when the wavefront blocks in the isthmus. Note the pause after interruption of the flutter with backup pacing at the atrial level.

Figure 6.

Twelve-lead ECG of interruption of the AFL. Note the progressive slowing of the flutter cycle and a marked pause after interruption with atrial backup pacing.

       If there is no complete isthmus block after interruption of the AFL, or when we start ablation in sinus rhythm, septal pacing induces a wavefront which passes through the isthmus and collides with the other wavefront coming from the high lateral wall, descending toward the lower part of the RA. Collision is almost always visible on the distal duo-decapolar catheter electrode pairs positioned at the level of the lower RA (Figure 7).

Figure 7.

Same abbreviations as in previous figures. Pacing from the Livewire™ Decapolar catheter proximal electrodes in the CS shows a collision front (*) in D4/3 when the wavefront coming through the isthmus in a clockwise direction encounters the one coming downward along the lateral wall of the RA, confirming the persistent conduction of the isthmus. On the distal ablation recordings (ABL D), we observe double potentials (A-A’) with insufficiently spaced intervals indicative of persistent local isthmus conduction.

       At that time, further applications of RF energy are directed toward sites where nearly fused double potentials are recorded on the ablation line during CS os pacing. When complete interruption of isthmus conduction is achieved, we observe a sudden shift of the collision front recorded on the distal duo-decapolar catheter electrodes, which changes to a straight alignment of the electrograms, indicating that the wavefront is exclusively coming from the upper part of the RA (Figure 8). This confirms the absence of conduction of the paced wavefront through the isthmus.

Figure 8.

During RF delivery at the site of the close-spaced double potentials during pacing at the CS os, the conduction through the isthmus slows with a time increase from 75 to 116 ms between the CS os and the first arrival at D1 on the lower lateral atrial wall. Suddenly, this time increases further to 155 ms due to the complete interruption of the clockwise conduction through the isthmus. The collision wave disappears. The potentials on the ABL leads have been markedly reduced by the RF delivery, but we may now observe widely separated double potentials (145 ms).

       This selective approach needs a straight and stable oriented ablation catheter, pulled back from the ventricular aspect of the isthmus to the vena cava junction. The RAMP-1™ introducer is very helpful in that respect, allowing not only firm contact of the ablation catheter tip, but also very precise orientation and stabilization, permitting a careful exploration of the isthmus line, avoiding shifts and torsions of the catheter. In this way, more precise targeting can be achieved and, consequently, the duration of the ablation procedure and X-ray exposure could be reduced. Overall, the ablation procedure does not exceed 10 to 15 minutes in the majority of cases with a minimum of RF applications.
       After having interrupted the isthmus, the duo-decapolar catheter is again placed on the isthmus with its distal end placed in or near the coronary sinus. Pacing from that site and from the low lateral atrial wall is initiated in order to confirm the absence of isthmus conduction in both directions (Figure 9).

Figure 9.

After having repositioned the Livewire™ Duo-Decapolar catheter on the isthmus and during pacing from the lateral aspect of the isthmus (D3), we aim to test the counter-clockwise conduction. We first observe a counter-clockwise wavefront arriving at D2 and in the isthmus. The wavefront blocking also travels upwards along the lateral wall of the RA (D4 to D10), descending along the septum, and arriving finally at the lower septum near the CS os (CS7-8) and at the opposite side of the isthmus (D1). The total delay is 225 ms, confirming the complete counter-clockwise block of the isthmus. The ABL D catheter on the isthmus records a similar delay (230 ms). The clearly separated double potentials (211 ms) are nicely visible on the ABL poles.

       In some instances, a marked slowed conduction through the isthmus can still be present despite an apparent complete interruption during the former pacing method with the recording catheter on the lateral wall. This can be revealed during careful analysis of clockwise and counter-clockwise conduction of the wavefront during pacing on both sides of the isthmus, while the duo-decapolar catheter is positioned on the isthmus, rather than on the lateral wall. After confirmation of complete block in the clockwise and counter-clockwise directions in the isthmus, a 15–20 minute wait time is observed during which a complete control electrophysiologic evaluation is performed. Afterwards, repeated pacing from both sides of the isthmus is performed, often after an isoprénaline infusion, for assessing the absence of reconduction, which might occur if ablation lesions are either superficial and/or incomplete.

Conclusions
       Ablation of CTI-dependent flutter has become a well-codified approach. The use of specific tools make it possible to refine and shorten the procedure and to improve the assessment of bidirectional conduction block. For this purpose, the Livewire™ Duo-Decapolar catheter is systematically used in our institution, not only for AFL, but for most of the ablation procedures because:
1. For AFL, the analysis of the electrical wavefront recorded by the duo-decapolar catheter permits a rapid confirmation of an isthmus related flutter, and can exclude left atrial flutter.
2. It has proven its handiness for easy positioning along the crista terminalis on the lateral RA wall, and more importantly, for a rapid insertion of its distal tip into the coronary sinus, which can almost always be catheterized without major difficulty. In AFL, this serves as a landmark for the introduction of another catheter for recording and pacing during ablation when the duo-decapolar catheter will be pulled back on the lateral RA wall. In these flutter patients, it indeed may sometimes be difficult to catheterize the CS because the atria are enlarged.
3. The duo-decapolar catheter as a landmark in the CS os allows us to orient more rapidly the CS catheter avoiding excessive X-ray exposure and time waste. Moreover, it gives us an almost complete mapping of the important sites of the RA and more specifically of the isthmus region, to avoid misinterpretation of bidirectional block during and after ablation. The sudden interruption of conduction clearly seen during RF delivery precludes further unnecessary energy applications.
4. Other ablation procedures may benefit greatly from this enhanced mapping. During pulmonary vein ablation in atrial fibrillation, an extensive view of atrial activation becomes available not only at the left atrial side (in the CS), but also on the right side.
In addition, the Livewire™ Duo-Decapolar catheter allows us distal CS pacing during ostial ablation and validation of left isthmus block.
5. During electrophysiologic evaluation of paroxysmal supraventricular arrhythmias, a careful mapping of atrial depolarization is readily achieved allowing fast diagnosis of accessory pathways, assessment of slow AV nodal pathway conduction and the activation sequence of atrial beats, thereby facilitating accurate diagnoses.’

       The RAMP-1™ introducer is specifically useful for AFL ablation because:
1. It permits fast angiographic imaging of the RA and isthmus before ablation.
2. It serves as an extremely useful tool for stabilizing the ablation catheter on the isthmus, especially in the complex anatomy of a long isthmus.
3. It permits enhanced tip-to-tissue contact avoiding partial ablation, edema formation and inefficient energy delivery.
4. A straight ablation lesion may be formed precisely, achieving more rapid and complete isthmus conduction block, preventing irregular ablation lines.

       In summary, the use of adequate tools greatly facilitated our ablation procedures, not only in terms of efficacy, but also by reducing whole procedure and fluoroscopic time.
       Further studies are underway to evaluate the efficacy of the RAMP-1™ approach versus common non-guiding introducer techniques.

Acknowledgments. The authors would like to express thanks to Benoit Collet, Electrophysiology Technician, Gladys Alsteen and Isabelle Manchi for collaboration and support.

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