Atrial Flutter A macro-reentrant atrial arrhythmia that is very regular with rates typically between 240 and 350 bpm1. There are several recognized variations of atrial flutter. 1. Schamroth, L. The Disorders of Cardiac Rhythm. Oxford, UK, Blackwell Ltd, 1971, p 49.2
Proposed Classification of Atrial Flutter A NASPE position paper proposed an open classification – Typical AFL (CCW) – Reverse Typical AFL (CW) Saoudi, N, Cosio, F, Waldo, A, et. al. JCE Vol. 12, No. 7, pp.852-866, July, 20013
Cardiac Anatomy TA ER/EV ISTHMUSNetter, F. Clinical Symposia. Novartis Pharmaceuticals Corporation, Summit, NJ, 1997.Atrial Flutter is a reentrant tachycardia in which the reentrantcircuit is contained in the right atrium. The isthmus is formed bythe IVC and Eustachian ridge/valve (ER/EV) on one side and theTA on the other. Conduction during fast rates cannot transversethe ER/EV. 4
Typical Atrial Flutter (CCW) In typical AF the reentrant circuit revolves around6 the tricuspid annulus in a counterclockwise pattern
Reverse Typical Atrial Flutter (CW) In reverse typical the reentrant circuit revolves7 around the tricuspid annulus in a clockwise pattern.
Electrogram Recognition Rate P wave morphology 12 Lead On the surface ECG it may often be very difficult to see the flutter waves. This may be overcome with vagal maneuvers or Adenosine administration.8
Electrogram Recognition Isthmus dependent Typical Atrial Flutter (CCW) – Atrial rhythm: regular and very stable (240-340 bpm) – P wave:Characteristic sawtooth pattern with a negative deflection in, II and III, and/or aVf (inferior axis) and positive in V1 (but may be negative or biphasic). Leads I and aVL show low-voltage deflections – Ventricular rate: usually 2:1 in both typical and reverse typical aflutter (higher degrees of AV block can occur in patients with AV nodal block disease or increased vagal tone)10
Electrogram : Reverse Typical AFL On the surface ECG typical atrial flutter looks similar to reverse typical flutter, however in Reverse Typical Aflutter (CW), the p-waves appear to be mostly positive in the inferior leads (II, III, aVf). P waves display an superior axis. Wide, negative deflections in V1 (may be most specific diagnostic sign) May demonstrate atypical p -wave morphologies12
Catheter Positions Catheter position varies from lab to lab Quadripolar at the His (to define septum/HBE) Multipolar in the CS (to define CS ostium, and perform septal pacing) Multipole (Duo-Decapolar™) at the RA (to define activation anterior/lateral to CT and isthmus). This may eliminate the HRA and CS catheters Quadripolar at the RVA (safety pacing) optional Exploring/Rove (mapping/RFA)14
Typical Atrial Flutter Typical AFL Reverse Typical AFL A 20 pole catheter placed around the TA with the distal pair of electrodes near the posterior free wall and proximal pair, the anterior septum, reveals counterclockwise activation around the TA in typical AF, and clockwise in reverse typical AF.17
Pre Ablation Methods and Strategies Induction – Conduction barriers – Diagnosis Mapping Entrainment Pacing maneuvers Strategy – Pacing maneuvers in SR Base line measurements (Pre and post comparison)18
Atrial Flutter Induction Induction methods for flutter include: – Extrastimulas testing – Atrial burst pacing – Isoproterenol Induction or termination using rapid atrial pacing may also induce atrial fibrillation (due to short cycle lengths)19
Intracardiac Electrogram Recognition – CCW Mapping Sequential activation around the right atrium20
Intracardiac Electrogram Recognition – CW Mapping Sequential activation around the right atrium21
Management of Typical and Reverse Typical AFL Medication – Control the ventricular response – Convert to sinus rhythm Anticoagulation Atrial overdrive pacing Cardioversion AV node ablation Isthmus RF ablation27
AV Node Ablation In some situations medical therapy and ablation attempts are unsuccessful. In circumstances it may be necessary to ablate the AV node and implant a permanent pacemaker.28
Goal of RF Ablation of Atrial Flutter The goal of RF ablation is the elimination of conduction within the critical zone of the reentrant circuit necessary to sustain atrial flutter. Tachycardia may be terminated by one lesion point along the Isthmus however this method is associated with a high recurrence rate In any of the targeted ablation areas, the key to success is a contiguous, transmural lesion from one anatomic barrier to another29
Ablation Methods and Strategies Methods – Point by point – Drag (Linear lesion) Strategy – During SR No acute end point – During SR with CS pacing Shift in activation – During tachycardia Termination of tachycardia30
Orientation During RF Ablation Atrial flutter ablation is anatomically guided along with electrogram verification of the LAO location between the: – Tricuspid annulus (TA) and CSos (septal isthmus: 5 oclock ) – TA and inferior vena cava (IVC) (posterior isthmus: 6 oclock) – TA and IVC (lateral isthmus 7 oclock) No matter whether it is typical or reverse typical AF, the ablation sites are always either the septal or posterior isthmuses. However, ablation can be performed anywhere along the isthmus, from the entrance to the exit of the 31isthmus.
Ablation Sites TV CS Long distance IVC Short distance but more ４：３0 but many smooth septal isthmus valleys 7：00 lateral isthmus 6：00 posterior isthmus LAO32Nakagawa. H., et al., “Role of the Tricuspid Annulus and the Eustachian Valve/Ridge on Atrial Flutter: Relevance to Catheter Ablation of theSeptal Isthmus and a New Technique for Rapid Identification of Ablation Success.” Circulation. 1996;94:407-424.
Ablation Challenges: Variability of Trabeculated Isthmus Blood pool Non-uniformity of the Posterior Isthmus – highly variable trabeculated patterns found inferior to the Cs ostium as well as at the inferior rim of the Cs ostium within the “flutter isthmus” Eustachian valve and ridge 5. Nakagawa. H., et al., “Role of the Tricuspid Annulus and the EustachianWaki, K. et.al. JCE Vol 11. No 1 January 2000 pg 92 Valve/Ridge on Atrial Flutter: Relevance to Catheter Ablation of the Septal Isthmus and a New Technique for Rapid Identification of Ablation Success.” . 33 Circulation. 1996;94:407-424.
RAMPTM Sheath for Access to the sub- Eustachian recess34
Catheter ablation of the Posterior Isthmus RAO LAO ablation catheter ablation catheter SVC SVC CSo IVC37 IVC
Ablation technique Catheter – Normally an 8mm tip ablation catheters is used, but for very thick or problematic isthmuses, an irrigated ablation catheter can be used. – Some doctors may even use a 4mm tip, but it will be a longer procedure and recurrence may be higher Electrogram criteria – Initial lesion point should show big V small A. – Electrogram should be evaluated after each point ablation. (Point by point ablation) – Observe for a decrease in the electrogram amplitude and keep ablating spots with significant A waves Use pacing maneuvers to assess the creation of complete isthmus conduction block38
Fluoroscopic Orientation During RF Ablation Ablation of the isthmus in either the RAO or LAO projection LAO projection allows identification of the position in a “clockface” relative to the location of the TVA (point to point) LAO projection allows visualization of the RF catheter as it is withdrawn into the IVC RAO projection allows discrimination of the Anterior (TVA), initial position, to Inferior (IVC), final position, during creation of the lesion in the isthmus39
Further Considerations during AFL Ablation RF Power considerations – With 4mm tip ablation catheters, 30-50 Watts will be adequate, but 8mm tip catheters often require more than 50 Watts Anatomical considerations – Convective effects of blood pooling and variable, complex anatomy may require higher power applications – Patient discomfort in region of IVC due to stimulation of nerve plexus 40
Ablation End Point Termination of the clinical arrhythmia – With this criteria alone there is a high recurrence rate Inability to re-induce atrial flutter; Confirmation of Bi-Directional block. – Pre and post timing – Block indicated by a multipolar catheter41
Summary of Complete Bi-Directional Block 19-20 Ablation CT LLRA 1-2 CS Pre Post 19-20 19-20 CS Pacing Site 1-2 1-2 19-20 19-20 LLRA 1-2 1-249
Other Methods to Confirm Bi-directional Block Vector Mapping with the BDB Catheter Searching for Gaps in the Blockline Differential Pacing50
Vector Mapping with the BDB CatheterBDBIsthmus ABL Catheter 51 Electrogram Polarity and Cavotricuspid Isthmus Block During Ablation of Typical Atrial Flutter.Tada,H. Oral, H. et al. Journal of Cardiovascular Electrophysiology. Volume12, No. 4, April 2001. P.394.
Vector Mapping with the BDB Catheter Vector mapping to confirm the blockline52 (Electrogram Polarity and Cavotricuspid Isthmus Block During Ablation of Typical Atrial Flutter）
Searching for Gaps in the BlocklineWhen you pace on one side of the blockline and you will notedouble potentials along the line where you have made acomplete line. However, where there is a gap as you slowlymove the catheter, you will note that the double potentialsdisappear meaning that you are on the Gap. You might alsofind fractionated potentials. You can also look for the sites withlarge electrograms meaning they have not yet been ablatedand ablate at those site.53
Searching for Gaps in the Blockline <90 >110 ms msTada et al.* reported that the interval separating the twocomponents of a double potential was useful to distinguishcomplete (>110 ms) from incomplete isthmus block (<90 ms)in patients undergoing radiofrequency ablation of typical atrialflutter.* Tada H et al. J Am Coll Cardiol 2001; 38:750-554
Differential Pacing to Confirm the Bloclline <90 ms <90 ms Eustachian Eustachian Low Ridge Low Ridge Lateral CS Lateral CS right right Atrium Atrium Tricuspid Annulus Tricuspid AnnulusPre-ablation – No Blockline• CS pacing – measure the time it takes for the conduction impulse to reach the catheter located at the LLRA.• LLRA pacing - measure the time it takes for the conduction impulse to reach the proximal electrodes of the CS catheter. 55
Differential Pacing to Confirm the Block line >110 ms >110 ms Eustachian Eustachian Low Ridge Low Ridge Lateral CS Lateral CS right right Atrium Atrium Block line Tricuspid Annulus Tricuspid Annulus Post-ablation – Block line • CS pacing – measure the time it takes for the conduction impulse to reach the catheter located at the LLRA. • LLRA pacing - measure the time it takes for the conduction impulse to reach the proximal electrodes of the CS catheter. • A 50% increase in the transisthmus conduction time from baseline is also56 predictive of complete block.