Surgery for Atrial Fibrillation

Seoul National University Hospital

Department of Thoracic & Cardiovascular Surgery

Mechanisms of Atrial Fibrillation Etiology Incompletely understood pathogenesis. Ectopic foci, single circuit reentry, multiple circuit reentry have been implicated in initiating and maintaining the condition Prerequisite ; substrate & trigger 1. Substrate is an atrial abnormality, frequently inflammation or fibrosis causes atrial electrical dysfunction that favors development of AF 2. Triggers include atrial ectopic foci, changes in atrial wall tension, and alterations in autonomic tone 3. Although substrate & trigger may vary, evidence points to the primary importance of pulmonary veins and left atrium initiating & maintaining

Origin of Atrial FibrillationParoxysmal AF

Originates from ectopic beats in the pulmonary veins in 94% of cases .

This likely relates to the anatomic transition from pulmonary vein endothelium to left atrial endocardium; at this junction, two types of tissue with different electrical properties are juxtaposed and this may potentiate development of AF.

Although there is the critical importance of pulmonary vein in patients with paroxysmal AF, it may not apply to persistent or permanent AF.

As regards persistent & permanent AF Direct evidence is lacking , but clinical experience implicates the posterior left atrium & possibly the pulmonary veins in their pathogenesis and maintenance .

And in most patients, the left atrium acted as the electrical driving chamber

Intermittent Atrial Fibrillation

• Induction of atrial fibrillation by a premature atrial beat originating in the orifice of one of the pulmonary veins

Intermittent Atrial Fibrillation

• Once induced, all atrial fibrillation is characterized by the presence of multiple macroreentrant circuits in the atria.

Intermittent Atrial Fibrillation

• Trigger for the induction of intermittent atrial fibrillation is located in the pulmonary veins in 90% of patients & outside the pulmonary vein area in 10% of patients.

Intermittent Atrial Fibrillation

• Each subsequent episode of atrial fibrillation requires another premature atrial beat to initiate the episode, with the trigger again being the pulmonary veins in the majority of cases.

Re-entry & Implications for AF

(Allessie, 1977)

Origin of Sinus Tachycardia Impulses

Atrial Fibrillation

Clinical Significance of AF

• AF affects nearly 1% of the general population, with a striking increased incidence in the elderly.

• High morbidity & increased mortality rates because of tachycardia-induced cardiomyopathy, hemodynamic compromise, & thromboembolism, causing serious health concern &financial costs.

• The aims of treatment are resortation of normal sinus rhythm, normal atrial contraction & atrioventricular conduction, rate control, and prevention of thromboembolic complications.

Preoperative Assessment for AF

Being considered for Maze procedure• Evaluation of ventricular function either by ech

ocardiography or contrast ventriculography• Coronary angiography for those older than 40 y

ears & with risk factors• Concomitant heart diseases should be evaluated• Patients with paroxysmal flutter or fibrillation s

hould be evaluated electrophysiologically for AV reentrant circuit

Intermittent Atrial FibrillationPulmonary Vein Isolation

• Simple pulmonary vein encirclement will cure 90%. However, 10% of patients with intermittent AF will not be cured with simple pulmonary vein isolation.

Continuous Atrial Fibrillation

• Failure of pulmonary vein isolation in patients with continuous atrial fibrillation

Surgery for Cardiac Arrhythmias

• Isolation procedures do not actually terminate arrhythmias but rather confine them, their trigger mechanisms, or both to a desired region of the heart to minimize their adverse effects.

• Ablation procedures preclude arrhythmias from developing either by destroying their trigger mechanism or by altering (or removing) the substrate that allows the arrhythmia to be induced and maintained.

Surgical Isolation Procedures

• Elective His bundle ablation for any type of supraventricular tachycardia

• Left atrial isolation procedure for automatic left atrial tachycardias and atrial fibrillation

• Right atrial isolation procedure for automatic right atrial tachycardias

• Corridor procedure for atrial fibrillation • Right ventricular isolation procedure for nonis

chemic ventricular tachycardia• Pulmonary vein isolation for the intermittent at

rial fibrillation

Surgical Ablative Procedures

• Surgical intervention for the Wolff-Parkinson-White syndrome, which interrupts macroreentrant circuit

• Discrete cryosurgery for atrioventricular node reentry tachycardia, which interrupts microreentrant circuit

• Focal cryoablation for automatic atrial tachycardias, which destroys the trigger mechanism

• Endocardial resection for ischemic ventricular tachycardia, which removes the microreentrant circuit

• Endocardial cryosurgical procedures for ischemic ventricular tachycardia, which destroys the microreentrant circuit

• Maze procedure for atrial fibrillation, which destroys macroreentrant circuits

Ideal Ablative Procedures

• Elimination of AF as an arrhythmia

• Restoration of sinus rhythm

• Maintenance of AV synchrony

• Restoration of atrial transport function

• Elimination of thromboembolic risks

Ablative Procedures

Ablation for Supraventricular Arrhythmias• Right atriofascicular accessory pathways• Ebstein’s anomaly• Coronary sinus abnormalities• Triangle Koch & AV node-His bundle (AVNRT)• Atrial tachycardia of ectopic origin• Atrial flutter • Atrial fibrillation

Indications for Maze Procedure

Failure of medical therapy as a result of

• Symptomatic intolerance of the arrhythmia despite phamacologic rate control

• Inability to achieve satisfactory phamacologic rate control

• Patient intolerance of requisite drug therapy• Occurrence of at least one previous thromboemb

olic episode

Surgical Techniques for AF

• Cox-Maze III

• Partial Mazes

• Radiofrequency

• Microwave

• Cryothermy

Assessing Results of AF Surgery

Permanent AF• Detection requires at least 2 EKG examination separated by 7 days or mo

re• Data analysis is done after 6 months more because atrial healing and stabi

lization of rhythm may take up to 6 months after surgery

Surgical failure• Presence of AF at 6 months or more after operation that is permanent or

paroxysmal and unresponsive to antiarrhythmic medication

Prevalence of AF• Paroxysmal, persistent, or permanent

Other events• Stroke, pacemaker implantation(sick sinus syndrome), atrial dysfunction

(atrial activity)

Map of Maze I Procedure

• Two dimensional original maze I procedure

Map of Maze II Procedure

Map of Maze III Procedure

Maze III Procedure

Maze III Procedure

Maze III Procedure

Maze III Procedure

Maze III Procedure

Maze III Procedure

Maze III Procedure

Maze III Procedure

Maze III Procedure

Standard Maze III Procedure

• The 5 left atrial lesions of the standard maze III surgical procedure for atrial fibrillation.

Mini-Maze Procedure for AF

• Pulmonary vein encircling incision, left atrial isthmus lesion with coronary sinus lesion, & right atrial isthmus lesion

Postoperative Complications

• Atrial dysrhythmias, flutter & fibrillation

• Sinus node dysfunction

• Blunted tachycardia response to exercise

• Absence of detectable sinus activity

• Complete heart block

• Early postoperative fluid retention

• Postoperative pericardial effusion

Results of Surgery for AF

• Cox-Maze III 1. Late freedom from AF is around 90% (Cox group;98%) 2. Temporary postoperative AF is common(30~40%) due to shortened atrial refractory period & did not diminish longterm results(return sinus rhythm over ensuing 3 months) 3. 15% require new pacemaker therapy 4. Atrial transport function in 98%(Rt),93%(Lt)

• Partial Mazes 1. Restore sinus rhythm around 80% 2. Increased risk of atrial flutter, usually right origin(5~10%) 3. Radial incision approach provides results comparable to those of Cox-Maze III 4. More effective restoration of atrial transport function

Results of Surgical Treatment

1. Cox-Maze procedure: Cox & Colleagues @ Among 346, 2% op.mortality, AF was cured in 99%, 2% required long-term postoperative antiarrhythmic medication @ Successful ablation was unaffected by presence of mitral valve disease, LA size, type of AF @ Temporary postoperative AF in 38% @ New pacemaker was required in 15% @ RA transport function in 98%, LA transport function in 93%

2. Cox-Maze III: Other centers @ Around 90% of late freedom from AF Cured AF in 75-82% in most series of mitralvalve surgery+ Cox-Maze III @ Amplitude of the AF wave and diameter of the LA : independent predictors of sinus restoration after operation

Coexistence of Sinus Rhythm & Segmental Atrial Fibrillation after Maze

Partial Maze Procedures

“Simple left atrial procedure” (Sueda et al. 1996) “Partial Maze procedure” (Takami et al. 1999) “Mini-Maze” (Szalay et al. 1999)More simplified, take less time, use alternative energy sourcesInclude some of the incisions and cryoablation le

sions of the Cox-Maze III, but not allFocus on the left atrium, including PVI, LAA excis

ion or exclusion

Energy Sources for Ablation Radiofrequency• Alternating current of 350 KHz to 1 MHz to heat the tissue • Heating tissue for approximately 1 minute at 70~80C produces lesions 3 to 6 mm deep to create a transmural line of conduction block by tissue vaporization and surface cooling Microwave• Thermal damage & subsequent scar formation , by high-frequency electromagnetic radiation(microwave) causes oscillation of water molecules in tissues, converting electromagnetic energy into kinetic energy(heat)• Depth & volume of heated tissue are greater than radiofrequency, and not char the endocardial surface Cryothermy• Application of nitrous oxide-based cryoprobe to atrial tissue for 2 minutes at -60C produces a transmural lesions , leaving a smooth endocardial surface

Radiofrequency (RF)

• Uses alternating current of 350kHz to 1 MHz to heat tissue

• Experimental data : 1min at 70-80°C produces 3-6mm deep lesions

• Unipolar vs. bipolar system

• Dry vs. SIRFMM

• Multiple RF systems : long flexible, rigid, pencil-like probes with a cool tip, bipolar clamp

• Either epicardial or endocardial ablation

• Time : 10-20 min for creation of left-sided lesion sets vs. 1hr. for Cox-Maze procedure

Surgical Techniques for RF

Radiofrequency Ablation

Bipolar RF

Microwave• Interest is growing in microwave energy

• High-frequency electromagnetic radiation causes oscillation of water molecules in tissue, converting elctromagnetic energy into kinetic energy (heat).

• Depth and the volume of heated tissue are greater, resulting in a higher probability of transmural lesions

• No char, which may reduce risk of thromboembolism

• Shielded probes produce safe epicardial ablation

• Available probes : 2-,4-,10 cm

• Energy set at 65W, 45 second application time

(Gillinov AM et al. Ann Thorac Surg 2002;74:1259-61)

Microwave System

• The FLEX 2™, FLEX 4™ and FLEX 10™ Microwave Ablation Probes are sterile, single-use, hand-held, surgical devices used exclusively with the AFx Microwave Generator

Cryothermy

• Well-established modality in arrhythmia surgery and an important component of the Maze III

• Nitrous oxide-based cryoprobe• 2min at -60°C reliably produces a transmural lesio

n that can be confirmed visually• Tissue architecture is preserved, leaving a smooth

endocardial surface• No flexible probe till now

Transmurality & Damaging Effect

• Discontinuous line allow AF breakthrough or potentiate development of atrial flutter

• Ensured transmurality : cut and sew, endocardial cryothermy, bipolar RF by measuring changes in tissue impedence

• Unipolar RF, epicardial cryothermy on a beating heart do not guarantee transmural lesions

• Esophageal injury has been reported • Thermal energy application should be avoided i

n thin, frail patients with delicate tissues

Results of Partial Mazes

Approximately 80% of patients restored

sinus rhythm Minor variations in incision pattern and

cryolesions do not influence the results Occurrence of atrial flutter is 5-10%

Results of Radiofrequency Ablations

Most series : mitral valve surgery + RF 70-80% of successful ablation Up to 60% of perioperative AF 30-40% of AF at discharge, but many return

to sinus rhythm over 3 months Atrial transport function in 80-100% who

return to sinus rhythm

Results of Microwave Ablations

Long-term results are unavailable; microwave catheter has only recently become available for intraoperative treatment of AF

Among 10 patients. who had mitral valve operations + MW of the pulmonary veins, 6 in NSR, 3 in AF, 1 under pacing at discharge

Approximately 80% of patients can be cured of AF

Energy Sources for Ablation

Type Endocardial Epicardial Flexible Assess No char Rapid application application probe transmural

Radiofreq. + + + + - +

Microwave + + + - + +

Cryothermy + + - - + -

* Radiofrequency energy may be delivered in unipolar or bipolar fashion

Surgical Option for Atrial Fibrillation

• Left atrial incisions of Cox-Maze III procedure

Surgical Option for Atrial Fibrillation

• Left atrial part of standard Cox-Maze procedure

Cox-Maze Procedure

• A; Cox maze III procedure

• B; Kosakai maze procedure

• C; Cryomaze procedure

Modifications of Maze Procedure

* Right & left atrium seen

from behind(A) & inside(B)

* Crossed lines;

modified atriotomies

* Dotted area; cryoablation

* Thick lines; SA node artery

* Right, left, posterior sinus node

arteries

Modifications of Cox-Maze III

• A; Modified procedure• B; Incision lines & impulse propagation after modified procedure

Modifications of Cox-Maze III

• A ; conventional Cox-Maze • B & C ; modification(usual & large atrium)• Crossed lines ; surgical atriotomies• Thick black lines ; cryoablation

Radiofrequency Modified Maze

• A; Lines of electrical activation• B; Zigzag lines depicting incision in the atria• C; Dotted lines depicting endocardial ablation

Radiofrequency Maze Procedure Right-sided Saline Irrigated

• A ; RA appendage excised• B ; Vertical incision• C ; Second longitudinal incision in RA• D ; Ablation line is created between cannulation

Radiofrequency Maze-Berlin Modification

• The incisions & sutures of the standard maze technique are replaced by radiofrequency ablation lines(dashed lines)

Radiofrequency Maze-Berlin Modification

• Dashed lines show position of radiofrequency maze lines of Berlin modification in comparison to the standard maze lines

AF Surgery Simplified with Cryoablation To Improve LA Function(I)

• Redundant, enlarged LA resected• i; incision to atrioventricular groove, j; cryoablation of coronary sinus

AF Surgery Simplified with Cryoablation To Improve LA Function(II)

• A; Anterior view of posterior left atrial wall• B; Posterior view of left & right heart• Cryoablation indicated by dotted lines

Bilateral Appendage-Preserving Maze

• A; Diagram of BAP-Maze procedure

• B; Impulse propagation pattern

• C; Diagram of Maze III

Radial Approach for Atrial Fibrillation

• Small circle indicates SA node, & shaded area indicates the isolated portion of the atrium

• Arrows indicate the activation wavefront from the SA node, radiating toward the annular margins

Radial Approach for Atrial Fibrillation

• Thick lines ; surgical incisions • Solid area ; atria surgically isolated or excised• Dashed lines ; Bachmann’s bundle between appendage, septum, a

nd crista terminalis• Arrows ; activation sequence

Radial Approach for Atrial Fibrillation

Maze procedure. Radial approach

MVR with Maze III

• A & B ; Left side incisions

MVR with Maze III

• Right side incisions, Maze III procedure

MVR with Maze III

Reduction Plasty with Maze

Reduction Plasty with Maze

Atrial Endocardial Maps after Maze

• The shaded area denotes electrically isolated region