Presentation on theme: "Atrial Flutter: An Electrophysiologic Overview"— Presentation transcript:
1Atrial Flutter: An Electrophysiologic Overview Welcome to ATRIAL FLUTTER – AN ELECTROPHYSIOLOGIC OVERVIEW. This module contains a discussion of the various characteristics of atrial flutter. ECG recognition and treatment of atrial flutter will also be explored. Focus is given to the use of radiofrequency (RF) ablation as a treatment for atrial flutter.MAJID HAGHJOO, M.DDEPARTMENT OF PACEMAKER AND ELECTROPHYSIOLOGYRAJAIE CARDIOVASCULAR MEDICAL AND RESEARCH CENTER (RCMRC)
2Objectives – Atrial Flutter Identify mechanisms and characteristics of atrial flutterRecognize ECG and intracardiac electrograms depicting different types of atrial flutterDiscuss treatment options for atrial flutter
3Outline – Atrial Flutter I. DescriptionII. CharacteristicsDefinitionTypes and featuresMechanismCircuit recognitionECG and intracardiac recognitionThis module will start by discussing the characteristics and ECG findings of atrial flutter.
4Outline – Atrial Flutter Pacing techniquesEntrainmentTreatment optionsRF ablationFuture directionsThe module will then discuss treatment options of atrial flutter, with an emphasis on RF ablation.
5Atrial Flutter Rapid and regular form of atrial tachycardia Usually paroxysmalMore common in men than women (M/F: 4.7:1).Sustained by a macro-reentrant circuit.In most cases, circuit is confined to the right atrium and left atrium is passive bystander.In some types of atrial flutter, arrhythmia circuit located in left atrium.Episodes can last from seconds to years.Chronic atrial flutter usually progresses to atrial fibrillation.Atrial flutter is a rapid and regular form of reentrant atrial tachycardia.It is usually paroxysmal, and it is sustained by a macro-reentry circuit located in the right atrial myocardium.Flutter episodes can last from seconds to years.Patients presenting with paroxysms of atrial flutter often have normal hearts, whereas patients with chronic atrial flutter usually have underlying heart disease. Chronic atrial flutter eventually converts to chronic atrial fibrillation.
6Atrial FlutterA unique population in which atrial flutter occurs commonly is in patients in the first week after open heart surgery (a third of postoperative SVTs)It is also seen in association with:chronic obstructive pulmonary diseasemitral or tricuspid valve diseasethyrotoxicosisrepair of congenital cardiac lesions in which the atria, most often the right atrium, is considerably incised, such as with the Mustard, Senning, or Fontan procedure or those with enlargement of the atria, especially right atrium.
7Reentry Circuit of Common Atrial Flutter Anatomic barriers within the right atrium sustain the macro-reentry circuit.The AV node plays no part in the flutter circuit, so drugs aimed at altering the conduction of the AV node have no effect on the atrial rate.Morady F. N Engl J of Med. 1999;340:
8Types and FeaturesFlutter Type Mechanism Atrial rate CureTypical * Counterclockwise RFAMacro-reentryReverse typical * Clockwise RFAAtypical Macro-reentry RFA* 90% of atrial flutters fall into the typical or reverse typical category.
9Mechanisms of A-Flutter Typical (counterclockwise and clockwise)A rapid and regular form of atrial tachycardia that is sustained by a macro-reentrant circuit which utilizes a cavotricuspid isthmusAtypicalAtrial reentry is independent from cavotricuspid isthmusMostly, reentry occur around scar tissue after surgeryIn some cases, reentry occur around left atriumDepending on the type of atrial flutter, the mechanism will vary. A discussion of each type of flutter follows, along with ECG and intracardiac recording examples. A macro-reentrant circuit can be defined as any arrhythmia pathway in which the electrical impulse travels through a relatively large region of tissue. Arrhythmias caused by macro-reentrant circuits often can be cured by ablation of a critical portion of the circuit.Atypical atrial flutter does not use the critical isthmus as used in Type I flutter.Macro-reentrant atrial tachycardia occurs frequently after surgery for congenital heart disease.
10Typical Flutter Mechanism: Induction: Termination: Counterclockwise macro-reentrant circuit that utilizes a cavotricuspid isthmus to sustain circuitInduction:Fast atrial pacing and/or the introduction of multiple premature beats near the low septumTermination:Rapid atrial pacing faster than the flutter rateCardioversionSpontaneousPharmacologic therapyWith counterclockwise flutter, a macro-reentrant circuit exists. This circuit is sustained by a critical isthmus.Induction of counterclockwise flutter can be accomplished with rapid atrial pacing and/or the introduction of multiple premature beats near the low septum.Termination of counterclockwise flutter may be accomplished with rapid atrial pacing, cardioversion, or with the use of medications, such as Ia, Ic, or class 3 antiarrythmic drugs.The arrhythmia may also convert spontaneously.
11Isthmus Conduction Typical Flutter The mechanism of counterclockwise flutter is further illustrated on this slide. A counterclockwise flutter circuit can travel between (A) the IVC (inferior vena cava) and CS (coronary sinus) os and/or (B) between the tricuspid annulus and the CS os. The key is that the isthmus is the critical portion of the circuit and the target for ablation.Typical FlutterConover: Electrocardiography. 4th ed. Mosby 1998; 75.
12ECG Recognition Typical atrial flutter Undulating atrial activity without a baselineAtrial rate: bpmRhythm: RegularVentricular rate: VariableDependent upon:AV node conduction propertiesUsually a 2:1, 4:1 fixed conduction ratioRecognition: “Sawtooth” appearance on the surface ECG (negative deflections in inferior leads and positive deflection in V1)Atrial flutter is distinguished from atrial tachycardia by the faster rate.1:1 AV conduction ratio in atrial flutter may be seen in: Wolf-Parkinson-White syndrome (most common); Lown-Ganong-Levine syndrome; Exercise; Catecholamine therapy; Phenytoin therapy; Class I antiarrhythmic drug therapy
13ECG RecognitionNotice the “sawtooth” pattern of the flutter waves in this rhythm strip. This is typical of counterclockwise atrial flutter. The atrial rate can be bpm. The ventricular response is fast, but it is regular.
14Other Methods of A-Flutter Recognition If diagnosis of atrial flutter is not clear from a standard ECG, any of a number of maneuvers can be useful:Vagal maneuvers (CSM, Valsalva maneuver)EGM recording by esophageal, transvenous, or epicardial electrodesPharmacologic agent: adenosine, esmolol, verapamil, diltiazem, or edrophonium. In the presence of wide QRS tachycardia, drug intervention to establish the diagnosis of atrial flutter is dangerous and contraindicated; DC cardioversion is indicated.Atrial flutter is distinguished from atrial tachycardia by the faster rate.
15Intracardiac Recording Typical Flutter This slide contains an intracardiac recording of counterclockwise flutter. In counterclockwise flutter, the crista catheter is draped around the lateral RA with the proximal catheter superior and the distal catheter inferior. As you can see from the activation sequence, the high crista is activated first then the low crista, then the CS proximal, and then the His.Texas Cardiac Arrhythmia, P.A.
17Reverse Typical Flutter Mechanism:Clockwise macro-reentrant circuit that utilizes a cavotricuspid isthmus to sustain circuitInduction:Fast atrial pacing and/or the introduction of multiple premature beatsTermination:Rapid atrial pacing faster than the flutter rateCardioversionSpontaneousPharmacologic therapyAs the name implies, with this flutter the macro-reentrant circuit is clockwise.Pacing techniques for induction and termination of this arrhythmia, are similar to those used in counterclockwise flutter.Treatment is similar to that discussed with counterclockwise flutter.
18ECG Recognition Clockwise atrial flutter Undulating atrial activity without a baselineAtrial rate: bpmAtrial rhythm: RegularVentricular rate: VariableDependent upon:AV node conduction propertiesUsually a 2:1, 4:1 fixed conduction ratioRecognition: “notched” upright pattern on the inferior surface ECG (positive deflections in inferior leads and negative deflection in v1)ECG characteristics of clockwise flutter are similar to those discussed in identifying counterclockwise flutter. A distinguishing difference is the pattern of the flutter waves. A “notched” upright pattern is often seen on the surface ECG inferior leads.
19ECG Recognition Texas Cardiac Arrhythmia, P.A. This slide shows a 12 lead ECG depicting clockwise flutter.Texas Cardiac Arrhythmia, P.A.
20ECG Comparison Counterclockwise Clockwise Note that the inferior leads (II, III and aVF) of counterclockwise flutter have a characteristic initial, broad “sawtooth” negative deflection followed by a less pronounced positive wave.In contrast, clockwise flutter has predominately upgoing flutter waves in the inferior leads that are typically notched and end with a slightly negative component.CounterclockwiseClockwiseZipes, catheter Ablation of Arrhythmias, Futura publishing
21Intracardiac Recording Reverse Typical Flutter This slide is an intracardiac recording of clockwise flutter. The crista catheter is positioned the same as noted in the counterclockwise recording of atrial flutter. Notice that the activation sequence is reversed from before. The low crista is activated before the high crista, then His A, and then the CS.Texas Cardiac Arrhythmia, P.A.
23Atypical Flutter Mechanism: Induction: Termination: Macroreentry that does not utilize cavotricuspid isthmusMacroreentry occur mostly around surgical incisionRare cases depends on functional barrierInduction:Atrial pacing at faster rates than the flutter rateTermination:Difficult with programmed pacingCardioversionPharmacologic therapyIn atypical flutter the reentry circuit may be confined to anatomic barriers including atrial tissue around the fossa ovalis, Bachman’s bundle, and the coronary sinus ostium. The true circuit for this type of flutter is unknown.Rapid, atypical atrial flutter may be a transitional rhythm between typical flutter and atrial fibrillation.Programmed pacing can convert the rhythm to atrial fibrillation. Ablation of true atypical flutter is not generally achievable at this time due to the unknown nature of the circuit.Pharmacologic therapy may consist of any drug that influences conduction velocity and the refractory period. The specific drugs are the same as with AFL.
24ECG Recognition Atypical atrial flutter Undulating atrial activity without a baselineAtrial rate: 340 to 433 bpmAtrial rhythm: Variable (flutter-fib)Ventricular rate: VariableDependent upon:AV node conduction propertiesRecognition:Very fast rate and variable cycle length on surface ECG, may progress to atrial fibrillationA difference in atypical flutter, when compared to counterclockwise and clockwise flutter, is the atrial rate and rhythm. In addition, this rhythm may progress to atrial fibrillation. Of note, some sources do not class this as “flutter”. Instead, it may be referred to as atrial tachycardia from a atriotomy scar, etc.
25Incisional Atrial Flutter Atrial rate: Sometimes variesMechanism: Incisional macroreentryComplication of surgeryCongenital heart diseaseTreatment: Ablated with good success using focused activation mapping to transect the isthmus of conductive tissueThe location of critical isthmus of conduction can vary depending on the location of the scarring. A thorough knowledge of the patient’s history of heart surgery is needed. This arrhythmia may be seen with big atriotomy scars like ASD repairs or with CABG surgery (where the RA is incised to go on bypass).
27Confirmation of Flutter Circuit Confirm direction of rotationDuring the EP study the direction of the flutter circuit should be confirmedFlutter should be present before the patient enters the lab, if not, attempts should be made to induce the tachycardiaDirection can be confirmed by using a multi-pole catheter positioned around the tricuspid annulus, and pacing near the isthmusThe direction of flutter is not as important as establishing isthmus dependence. Frankly, counterclockwise and clockwise are ablated the same. For some unknown reason, in clockwise flutter isthmus block is harder to obtain.
29Activation Sequence of Typical Atrial Flutter (LAO View)
30Fluoroscopic PA and LAO views of a multipolar reference catheter
31Concealed Entrainment Used to verify that isthmus is utilized by the tachycardiaPace the isthmus at a cycle length 20 to 40 msec shorter than the tachycardia cycle lengthNo change on surface ECGNo change on intracardiac recordingsTachycardia resumes its original cycle length upon termination of pacingBy pacing near the critical isthmus, entrainment pacing techniques can be used to verify that the isthmus is utilized, and therefore can be ablated. Concealed entrainment is observed when pacing at the critical isthmus. No changes should be observed in the flutter pattern on the surface ECG or the intracardiac recordings. The tachycardia will return to its original cycle length after termination of pacing.
34Treatment Options: Acute A-Flutter Pharmacologic therapyRapid Atrial PacingDirect Current CardioversionTwo separate goals are used to treat atrial flutter. The first goal is to terminate the flutter and prevent a recurrence. The second goal is to control the ventricular response during the arrhythmia.
35Treatment Options: Acute A-Flutter Pharmacologic therapy for rhythm controlIV ibutilideOral flecainide, single dose of 300 mgOral propafenone, single dose of 600 mgPharmacologic therapy for rate controlIV calcium channel blockers (verapamil, diltiazem)IV beta-blockers (esmolol)Two separate goals are used to treat atrial flutter. The first goal is to terminate the flutter and prevent a recurrence. The second goal is to control the ventricular response during the arrhythmia.
36Treatment Options: Acute A-Flutter Rapid Atrial PacingMethod of choice in postcardiac surgery atrial flutterPacing should be performed from high right atrium because the appearance of positive atrial complexes in ECG lead II is the hallmark of interruption of atrial flutterRamp pacing at a rate about 10 bpm faster than flutter rate and then gradually increased until the atrial complexes in lead II become positiveBurst pacing at a rate 120% to 130% of the flutter rate and continued for 15 to 30 seconds until the atrial complexes in lead II become positive; if flutter continued, pacing rate should be increased by 5 to 10 bpm.Recommended minimum duration of pacing is 10 seconds and stimulus strength of at least 10 mA is needed.When esophageal pacing is used : a duration of at least 9 to 10 ms and up to 30 mA in strength is needed. Pacing should be initiated at a relatively slow rate to demonstrate that no ventricular capture is inadvertently produced.
37Treatment Options: Acute A-Flutter Direct Current CardioversionContraindicated in patients after having recently eaten or those with COPDUsing a standard shock, at least 50 J is generally recommended. Because 100 J is virtually always successful and virtually never harmful, it should be considered as the initial shock.
38Treatment Options: Chronic A-Flutter Pharmacologic therapyCurrently class IA, IC and III antiarrhythmic agents have demonstrated efficacy in suppression of atrial flutter.In the absence of structural heart disease, class IC are the drugs of choice; class III likewise may be effective.Catheter ablation therapyTwo separate goals are used to treat atrial flutter. The first goal is to terminate the flutter and prevent a recurrence. The second goal is to control the ventricular response during the arrhythmia.
39RF Ablation of Typical Flutter Cavotricuspid isthmus is the target for typical and reverse typical flutter ablationThe endpoint of ablation is bidirectional isthmus block persisting for minutesThe precise point of the isthmus that the ablation line should cross is variable, however it is usually midway between the septal and the anterior RA (6 o’clock of the TR in a 45° LAO view)
40Oblique View of Right Atrium Superior Vena CavaCrista TerminalisFossa OvalisPectinateMuscleA review of landmarks is helpful, before discussing ablation techniques.EustachianRidgeOrifice of Coronary SinusInferior Vena CavaNetter F. Atlas of Human Anatomy. 1989;Plate 208.
41RF Ablation of Typical Flutter A linear lesion needs to be created to sever the macroreentrant circuitThe lesion starts from the tricuspid annulus and runs back to the IVCThe lesion must be constant and contain no skips, otherwise the circuit can remainTermination will occur during RF deliveryBi-directional block is confirmed for acute success. Ablation of isthmus dependent flutter (clockwise and counterclockwise) depends on complete, bi-directional block at the isthmus.
42Catheter Location for Atrial Flutter Ablation CristaFree wall
43Atrial Flutter Ablation AFL terminationThis slide depicts termination of atrial flutter during RF current delivery.
44Conduction BlockBefore the ablation, pacing near the CS os would allow the impulse to travel in both directions, eventually colliding on the lateral wall.After ablation, pacing near the CS os only allows the impulse to travel in one direction, eventually terminating at the line of block.Singer: Interventional Electrophysiology. Williams & Wilkins 1997; 367.
45Isthmus Block: Activation sequence during pacing Proximal CS pacingLow RA pacing
46Assessing isthmus block during CS pacing No blockNo CTI blockCTI block
47Other Markers of Conduction Block Increase in trans-isthmus conduction timedifferential pacingDouble potentialsms interval between potentials along entire ablation lineReversal of electrogram polarity on the opposite side of the ablation line from the pacing siteChange in p-wave morphology pacing lateral to the ablation lineThis slide summarizes potential markers of conduction block in the common flutter isthmus. First, an increase in trans-isthmus conduction time with differential pacing so that after block is achieved, pacing on one side results in a long conduction time to the opposite side.If you move the pacing site a little bit further from the line of block, you will see that the conduction time to the opposite side decreases when you have block. This increases when there still slow conduction through the flutter isthmus. Secondly, double-potentials, as we discussed, with a relatively long interval of more than 100 to 110 milliseconds between the two potentials. We like to see this present along the entire ablation line.If we move our pacing site a little bit further from the line of block, then the conduction time from the pacing site to the potential generated by the wave front activates the distal side of the line becomes shorter and that to the proximal side becomes a little bit longer and the opposite occurs if there is still conduction through the isthmus. Thirdly, reversal of the electrogram polarity on the opposite side of the line of block, when block is achieve, and finally one can also look for changes in P-wave morphology when pacing in the low lateral right atrium on the free wall side of the line of block and these are all reviewed nicely in the references listed at the bottom of this slide.On a daily basis, we find that interpreting the double-potentials and simply doing differential pacing is quite useful. There are times where the double-potentials are not easily detectible in the common isthmus, particularly if you have had to do a lot of RF and you have low amplitude signals everywhere through the isthmus. Then it is useful to have some of these other markers to help confirm when you have conduction block.
55Success Rates of Catheter Ablation of Atrial Flutter Acute Follow-up Long-Term Study # Success (%) (mo) Success (%)FeldCosioLeshCalkinsKirkorianFischerSteinbergPotySaxonCauchemezNakagawaPoty *Fischer
56Complications of Flutter Ablation Pain: especially if close to the septal RA- pain is usually controlled by IV sedationAV block: especially if RFA applicated close to low portion of Koch' triangle around the CS ostium- Av block may be related to vagal effect- AV block was completely reversible spontaneously or preventable by atropineThere are no report of tricuspid valve dysfunction or coronary artery obstruction
57Clinical course and recurrences Since adoption of isthmus block as an endpoint, recurrence rates less than 10% are commonly reported.Appearance of other types of flutter during follow-up is unusual.The main problem during follow-up is atrial fibrillation, usually paroxysmal form, in ≥ 30% of patients.
58SummaryAtrial flutter ablation is effective way for Atrial Flutter control with low risk of complications.Improved mapping techniques along with enhanced imaging will improve the success rate of flutter ablations.This module has discussed the various types of atrial flutter, along with treatment modalities. The use of RF ablation for atrial flutter is a new treatment option for selected patients with atrial flutter.