What is Atrial Fibrillation Insights from Catheter Ablation

1
What is Atrial Fibrillation? Insights from
Catheter Ablation

• Robert C. Kowal, MD/PhD
• HeartPlace
• Baylor University Medical Center

2
Clinical Relevance of Atrial Fibrillation

• Over 2 million affected
• Incidence increases with age
• gt10 in octogenarians

• Independent risk for CHF, stroke and mortality
• Incidence has increased over last 20 years

Wattigney Circulation 2003 and Framingham Study
3
Tale of Three Patients

• Patient 1
• 48 y/o with history of atrial flutter now with
  paroxysmal AF (gt50 episodes daily).
• Patient 2
• 55 y/o with palpitations, fatigue and persistent
  AF.
• Patient 3
• 23 y/o woman with 10 year history of palpitations
  and symptomatic and asymptomatic AF.

4
ECGs of Atrial Fibrillation
5
Classification of Atrial Fibrillation

• Paroxysmal AF
• Self-terminating episodes lasting lt7 days
• Persistent AF
• Episodes require chemical or electrical
  cardioversion
• Permanent/Chronic AF
• Attempts to maintain sinus rhythm futile
• Progression from Paroxysmal to Pers/Perm
• 8 at 1 year, 20 at 3 years

Humphries Circulation 2001 Levy JCE 2003
6
Atrial Fibrillation Begets AF

• Ease of induction and episode duration increase
  with time
• Remodeling
• Increase LA size
• Extracellular fibrosis
• Cellular
• Electrophysiologic
• Molecular

Baseline
Pers AF
Allesie Circulation 1995 Morrillo Circulation 1995
7
Progression of Atrial Fibrillation
Paroxysmal
Persistent
Permanent
Clinical
Structural
Mechanistic
?
8
Theories of AF Mechanism

• Multiple heterotopous centers
• Multiple Wavelet Hypothesis
• Continuous activation of the atrial myocardium
  by several wavelets (gt30) of excitation wandering
  around islets of functional obstacles.
• Self-sustaining
• Dependent of atrial size
• RA animal models
• 4-5 wavelets needed
• more waves, more persistence

Lewis, 1912 Moe, 1965 Allesie, 1985 Nattel, 2002
9
Re-emergence of Focal AF

• Paroxysmal AF often triggered by same PAC
• Most triggers map to PVs
• RF ablation could cure 70-75 of patients.
• Shift from focal ablation to PV isolation
• Complications
• Multiple triggers

Haissaguerre, NEJM. 1998
10
Re-emergence of Focal AF

• Paroxysmal AF often triggered by same PAC
• Most triggers map to PVs
• RF ablation could cure 70-75 of patients.
• Shift from focal ablation to PV isolation
• Complications
• Multiple triggers

Haissaguerre, NEJM. 1998
11
Pulmonary Veins as Triggers of AF

• Intrinsic pacemaker function
• Shorter refractory periods
• Fewer cell-cell interactions
• More susceptible to stretch and fibrosis
• Amenable to focal, triggered and re-entrant
  arrhythmia

12
PV Anatomy
13
PV Isolation
14
PV Isolation
15
En Bloc PV Isolation
16
Dissociated PV Activity
I
F
V1
PV
CSp
CSd
17
Patient 1 AF Trigger from RUPV
I
F
V1
RUPV
CSp
CSd
18
Non-PV Triggers of AF

• 28 of patients with Paroxysmal AF had non-PV
  sources of ectopy
• Locations
• Posterior LA (border of PV and LA)
• Crista Terminalis
• Ligament of Marshall
• SVC
• CS ostium

Chen, Circulation, 2003
19
Non-PV Triggers of AF
I
F
V1
Map
RIPV
CSp
CSd
20
Ablation of Non-PV AF Sites
I
F
V1
Map
CSp
CSd
21
Can a Trigger be a Driver?
I
F
V1
RUPV
CSp
CSd
22
AF Termination
I
F
V1
RUPV
CSp
CSd
23
Approaches to Persistent AF
Pappone, Circulation 1999 and 2001 Oral,
Circulation, 2003 Nademanee, JACC 2004
24
Mechanisms of Persistent AF

• Differences in activation frequency during AF
• Higher frequency sites in LA c/w RA
• Often occur at PV ostia, LAA, LA septum
• Activation at highest frequency sites likely due
  to vortex of reentry
• Rotors
• Leading circle reentry
• Remainder of atria cannot keep up leading to
  wave-brake and fibrilatory conduction
• Rotors may be anchored or drift, but tend to
  localize

Jalife, JCE 2003 Jalife, Cardiovascular Research,
2002
25
Dominant Frequencies in AF
26
Ablation of Persistent AF
Haissaguerre, Circulation, 2005
27
Patient 2 Organization and Ablation
I
F
V1
Map
CSp
CSd
28
How Much Tissue is Needed for AF?
I
F
V1
Map
RUPV
CSp
CSd
AF Confined to the Right Upper PV
29
Compartmentalizing Persistent AF
Rostock, JCE, 2006
30
Progression of Atrial Fibrillation
Paroxysmal
Persistent
Permanent
Clinical
Structural
PV, non-PV focal triggers/drivers
Rotors, drivers and fibrillatory waves
Mechanistic
Role of the Autonomic Nervous System
31
Patient 3 Atrial Tachycardia Mimicking AF
32
When is AF not AF?
33
Irregular AT Degenerates to AF
I
F
V1
His
CSp
CSd
34
Site of Tachycardia Termination
35
Ideal Candidates of AF Ablation

• Lone Paroxysmal Atrial Fibrillation
• Frequent symptomatic episodes
• Best if firing in the EP lab
• Failure of at least one AA drug
• LA size lt 5 cm
• Preserved EF
• No comorbid lung disease

36
Success Rates

• Definition
• No AF
• No AF on a previously failed medication
• Marked reduction in episodes and/or symptoms
• In ideal patients, 75-85
• Early recurrence
• Complications
• Tamponade
• Stroke
• PV stenosis
• Esophageal LA fistula

37
Less Ideal Patients

• Persistent/Permanent AF
• Unclear Symptoms
• Amiodarone challenge
• Large LA
• Depressed EF
• Comorbid lung disease/obesity
• I want to get off coumadin
• New Complication Atrial Flutter

38
Map of Left Atrial Flutter
39
RF Application
40
Future Directions Balloon Catheters
41
Cryo-Balloon Postioning
Left Upper Pulmonary Vein RAO View
42
Cryo Application
43
Pulmonary Vein Isolation
ECG
HRA
PV Bi
PV EBi
CSp
CSd
Pre LUPV Post
Pre LLPV Post
44
More of the Future

• Robotics
• Magnetic Navigation
• Image integration

45
Conclusions

• Atrial fibrillation is a complex process that is
  an electrical endpoint of varied mechanisms that
  change as the disease progresses.
• The advent of catheter ablation has helped define
  the mechanism of the arrhythmia by challenging
  our prior conceptions and provided new
  therapeutic options.
• Most AF starts with focal drivers/triggers,
  predominantly from thoracic venous structures.
• With electrophysiologic and cellular remodeling,
  the atrial milieu allows for the development of
  rotors and reentry with fibrillatory conduction.

46
Conclusions

• Remodeling then makes the rhythm progressively
  more refractory to therapy.
• The Autonomic Nervous System is a critical
  modifier of the above processes and may emerge as
  an additional target for ablation.
• In some patients, atrial tachycardias may precede
  the development of atrial fibrillation and may
  emerge as marker for future AF or a target to
  prevent future AF.

47
Conclusions

• Newer Technologies will a make AF ablation safer
  and more effective.
• Left atrial flutter after AF ablation and MAZE
  procedures are approachable with catheter
  ablation with excellent success.

48
PV Exit Block
I
F
V1
PV
CSp
CSd
49
Pulmonary Vein Isolation
ECG
HRA
PV Bi
PV EBi
CSp
CSd
Pre RUPV Post
Pre RLPV Post