Download Catheter Ablation in the Treatment of Atrial Fibrillation

Catheter Ablation
in the Treatment of
Atrial Fibrillation
Atrial Fibrillation
• First described in
1903 by Hering
• Most common
sustained arrhythmia
Atrial fibrillation accounts
for 1/3 of all patient
discharges
with arrhythmia as
principal diagnosis
6%
PSVT
6%
PVCs
18%
Unspecified
4%
Atrial
Flutter
9%
SSS
34%
Atrial
Fibrillation
8%
Conduction
Disease
10% VT
3% SCD
Baily D. J Am Coll Cardiol. 1992;19(3):41A.
2% VF
Atrial Fibrillation
• What is Atrial Fibrillation?
• Chaotic circular impulses in the atria
– Several reentrant circuits moving simultaneously
– Atrial rates
• 300 to 600 beats per minute
– Ventricular rates regulated by the AV node
• Irregularly irregular due to partial depolarization of AV
node
– Results in loss of AV synchrony
• 20% to 30% decrease in cardiac output
Incidence and Prevalence
• Prevalence increases with age
– 4.8 % in the 70-79 age group
• Increases to
– 8.8% in the 80-89 age group
• During the next 7-8 years, the number of
people over the age of 80 is expected to
quadruple
Atrial Fibrillation Demographics by Age
U.S. population
x 1000
Population with AF
x 1000
Population with
atrial fibrillation
30,000
500
400
U.S. population
20,000
300
200
10,000
100
0
0
<5
5- 10- 15- 20- 25- 30- 35- 40- 45- 50- 55- 60- 65- 70- 75- 80- 85- 90- >95
9 14 19 24 29 34 39 44 49 54 59 64 69 74 79 84 89 94
Age, yr
Adapted from Feinberg WM. Arch Intern Med. 1995;155:469-473.
Stages of Atrial Fibrillation
• Paroxysmal
• Persistent
• Permanent
Stages of Atrial Fibrillation
• Paroxysmal (23% of AF population)
– Self limiting
• Spontaneous conversion to sinus rhythm within 24 hrs
after onset is common
• Once the duration exceeds 24 hrs, the likelihood of
conversion decreases
• After one week of persistent arrhythmia, spontaneous
conversion is rare
– 30% of these patients develop “Persistent” AF
Stages of Atrial Fibrillation
• Persistent (38% of AF population)
– Requires intervention to restore normal rhythm
• Cardioversion
– Electrical or Chemical (drugs)
– Can lead to electrophysical and structural changes
in the myocardium (remodeling) that can lead to
“Permanent” AF
– AF with duration of greater than 7 days rarely
spontaneously converts
Stages of Atrial Fibrillation
• Permanent (39% of AF population)
– Unable to convert Electrical or Chemical (drugs)
Mechanisms of AF
• Theories of the mechanism of AF involve
2 main processes:
- Enhanced automaticity in one or several rapidly
depolarizing foci
- Reentry involving one or more circuits
Mechanisms Contributing to AF
Mechanisms of AF
• Rapidly firing atrial foci, located in one or
several pulmonary veins (PVs), can initiate AF
in susceptible patients
• Foci also can occur in RA and infrequently in
the superior vena cava or coronary sinus
Pulmonary Vein Myocardial
Sleeves
Factors Involved in the Pathogenesis of AF
• Studies in man have shown that increased inhomogeneity of
refractory periods and conduction velocity is present in AF
patients.
• Structural changes in atrial tissue may be one of the underlying
factors for dispersion of refractoriness in AF.
• Other factors involved in the induction or maintenance of AF
include premature beats, the interaction with the autonomic
nervous system, atrial stretch, anisotropic conduction, and the
aging process, vein of Marshall……….
Mechanisms contributing to AF
Atrial Fibrillation: Clinical Problems
• Embolism and stroke (presumably due to LA clot)
• Acute hospitalization with onset of symptoms
• Anticoagulation, especially in older patients (> 75 yr.)
• Congestive heart failure
–
Loss of AV synchrony
–
Loss of atrial “kick”
–
Rate-related cardiomyopathy due to rapid and irregular ventricular
response
• Rate-related atrial myopathy and dilatation
• Chronic symptoms and reduced sense of well-being
Therapeutic Approaches to
Atrial Fibrillation
• Anticoagulation
• Antiarrhythmic suppression
• Control of ventricular response
–
Pharmacologic
–
Catheter modification/ablation of AV node
• Curative procedures
–
Catheter ablation
–
Surgery (maze)
Antiarrhythmic Therapy for Atrial Fibrillation
• Advantages
• High efficacy for some
patients, at least
initially
(< 50% of all patients)
• Disadvantages
• High recurrence rate
• High long-term cost
• Non-curative
• Low initial cost
• Adverse effects
• Noninvasive
• Potential proarrhythmia
Antiarrhythmic Suppression
• Drugs
– Conversion of AF
• Class 1A (decrease conduction velocity, increase
refractory periods of cardiac tissue, suppress
automaticity)
– Quinidine
– Procainamide
• Class III (decrease conduction velocity, increase
refractory periods of cardiac tissue, suppress
automaticity)
–
–
–
–
Amiodarone
Sotalol
Ibutilide (Corvert)
Dofetilide
Antiarrhythmic Suppression
• Drugs
– Maintenance of normal rhythm
• Class 1A
• Class III
• Class 1C (decrease conduction velocity)
– Flecainide
– Propafenone
– Drug choice depends upon patient’s underlying
heart disease
Nonpharmacological Approaches to
Atrial Fibrillation
1. Pacemaker therapy
2. Ablation
3. Surgery
RF Ablation Techniques
A)
Focal ablation of PV (Pulmonary vein) triggers
B)
Segmental PV isolation
C)
Wide Area Circumferential Ablation
D) Ablation of Fractionated Complex Electrograms
E)
Targeted ablation of ganglionated autonomic plexi in the
epicardial fat pads
Focal Ablation of Triggers
Focal Ablation of Atrial Fibrillation
• 95% of foci are located within a pulmonary
vein ( PV).
• Focal sources of AF may be found in the RA,
LA, coronary sinus, superior vena cava or vein of
Marshall.
Haissaguerre M, Jais P, Shah DC, et al. Spontaneous initiation of atrial fibrillation by ectopic
beats originating in the pulmonary veins. N Engl J Med 1998;339:659–66.
Chen SA, et. al: Initiation of atrial fibrillation by ectopic beats originating from the pulmonary
veins: Electrophysiologic characteristics, pharmacologic responses, and effects of
radiofrequency ablation. Circulation 1999;100:1879-1886.
Pulmonary Vein Spike Discharges
Pulmonary Vein Spike Discharges
Initiation of AF by PV Discharges
PV Potentials
PV potentials
PV Potentials
PV Potential on 6-10
PV potentials
disappeared
during
radiofrequency
current
application
Loss of PV Potentials
Focal Ablation of Pulmonary Veins
Complications
• The most common complications associated with the
focal ablation of the PVs are pericardial effusion
(<4%), transient ischemic episodes (<2%) and
symptomatic PV stenosis <2%).
• Asymptomatic PV stenosis may occur at as many as
40% of sites at which focal ablation is performed.
• Symptomatic PV stenosis seems to be infrequent if
the number of radiofrequency applications delivered
within PV is kept to a minimum.
PV Stenosis
PV Stenosis
Multi-slice CT Endocardial View
PV Stenting
Tamponade: Intra-cardiac echo
The incidence of perforation during ablation of the left atrium is relatively low
Segmental PV Isolation
Segmental PV Isolation
• Limitations associated with focal ablation have
prompted the development of other techniques for
eliminating the PV arrhythmias.
• Anatomically PV isolation has significant advantages
over focal ablation.
Lasso or Spiral Catheters
Dissociation of the
PV potential after
successful isolation
Segmental Ostial Pulmonary Vein
Isolation
• The initial experience with segmental ostial
ablation of PVs guided by PV potentials is
encouraging, with a long-term success rate of 90%
in patients with paroxysmal AF
• Minimal risk of PV stenosis when the power of
radiofrequency energy applications is limited to 30
W.
Wide Area Circumferential
Ablation
Circumferential Ablation
• It is an anatomic approach in which circumferential lines of
block are created using 3D maps ( Carto, NavX..) around the
ostia of PVs for isolation of PVs from LA.
• Additional linear lesion from LIPV to mitral annulus for
preventing LA incisional tachycardia ( 2%).
• Additional linear lesions (posterior, roof, right isthmus….)
may be created deepening on operator’s preference.
Pappone C, et al. Atrial electroanatomic remodeling after circumferential radiofrequency
pulmonary vein ablation: efficacy of an anatomic approach in a large cohort of patients with
atrial fibrillation. Circulation 2001;104:2539–2544.
NavX Map
Anatomical Reconstruction of LA
Circumferential Ablation
Circumferential Ablation
Carto Map
Circumferential Ablation
Circumferential Ablation
Circumferential Ablation
Magnetic Resonance Image
Electroanatomic Map
Circumferential Ablation
• Effective in both paroxysmal and chronic AF
(81%, 76%)
• Bipolar amplitude < 0.1 mv inside and around
the lesion may be acceptable for showing PV
isolation.
Post Circumferential PV ablation
Bipolar
amplitude
< 0.1 mv
inside the
lesion
Mitral Isthmus Line
The addition of mitral isthmus line to the PV
disconnection may allow a significant improvement of
sinus rhythm maintenance rate, particularly in patients
with persistent AF, without the risk for major
complications.
J Cardiovasc Electrophysiol, Vol.
16, pp. 1150-1156, November 2005
Complication rates following circumferential
pulmonary vein ablation
•
•
•
•
•
•
•
•
•
Death
0%
Pericardial effusion 0.1%
Stroke
0.03%
Transient ischemic attack
0.2%
Tamponade
0.1%
Atrio-esophageal fistula
0.03%
Pulmonary vein stenosis
0%
Incisional left atrial tachycardia
6%
Phrenic nerve injury
Topographic
Variability of the
Esophageal Left
Atrial Relation
CT
reconstruction
of the LA, the
pulmonary
veins, and the
esophagus
Topographic Variability of the
Esophageal Left Atrial Relation
Phrenic Nerve Injury
Ablation of Fractionated Electrograms
• Hypothesis being that these are consistent sites where
fibrillating wavefronts turn or split.
• By ablating these areas the propagating random
wavefronts are progressively restricted until the atria
can no longer support AF.
• Nademanee demonstrated 70% freedom from AF
following a single procedure for permanent AF
patients.
Nademanee K, et al. A new approach for catheter ablation of atrial fibrillation: mapping of the
electrophysiologic substrate. J Am Coll Cardiol 2004;43:2044–53.
Segmental Ablation vs. Circumferential Ablation?
• Is either of the two ablation strategies superior to the other?
• Oral et al. showed that, during the 6 months following a single
catheter procedure, Circumferential Ablation was associated
with a significantly better outcome with no differences
between the two ablation strategies in the complication rates.
• Schmitt et al. reported opposite results to those of Oral et al.
• The opposite results in the two studies were obtained because
of the large variability in the success rate observed in patients
undergoing Circumferential Ablation (88 vs. 47%) while the
success rates in patients undergoing Segmental Ablation
remained unchanged (67 vs. 71%).
Integrated Approach
Journal of Cardiovascular Electrophysiology Vol. 16, No. 12, Dec. 2005
Frequently Asked Question
Who is currently a candidate for
AF ablation?
Patient selection criteria
• Inclusion criteria
•
•
•
At least one monthly episode of persistent symptomatic AF or
At least one weekly episode of paroxysmal AF or
Permanent AF
And
• At least one failed trial of antiarrhythmic drugs or
• More than one antiarrhythmic drug to control symptoms
• Exclusion criteria
•
•
•
•
•
•
•
NYHA functional class IV
Age > 80 years
Contraindications to anticoagulation
Presence of cardiac thrombus
Left atrial diameter ≥ 65 mm
Life expectancy < 1 year
Thyroid dysfunction
• Recent updates
•
•
Patients with mitral and/or aortic metallic prosthetic valves are
not excluded
Previous repair of atrial septal defects is not an absolute contraindication
Frequently Asked Question
AF ablation for asymptomatic
individuals?
Asymptomatic Patients
• To date there is no evidence that treatment of AF by ablation
improves mortality, although there are uncontrolled data
suggesting that this may be the case.
• Therefore, asymptomatic patients should not be offered
curative ablation of AF, except in the case of those patients
undergoing cardiac surgery who may benefit from surgical
ablation of their AF as an adjunctive procedure.
• There is also evidence that patients with heart failure have
significant improvements in left ventricular function
following successful catheter ablation of AF.
Conclusion
• For many patients with a previously untreatable heart
rhythm, ablation has dramatically improved their symptoms
by restoring and maintaining sinus rhythm.
• Preliminary randomized studies of catheter ablation of AF
provide evidence that ablation (with or without concurrent
anti-arrhythmic drug use) effectively improves maintenance
of sinus rhythm when compared with current antiarrhythmic drugs.
• Although prognostic and quality of life data from long term
randomized trials of catheter ablation for AF are still in
preparation, the non-randomized data comparing ablation to
continued medical treatment suggests a strong benefit from
ablation.
Tehran Arrhythmia Center
WWW.IranEP.org
[email protected]