MINISTRY
MINISTRY
OF EDUCATION AND TRANING
OF NATIONAL DEFENCE
MILITARY MEDICAL UNIVERSITY
PHAM TRAN LINH
STUDY ON ELECTROPHYSIOLOGICAL
PROPERTIES AND THE EFFICACY OF
CATHETER – BASED RADIO FREQUENCY
ABLATION OF PAROXYSMAL ATRIAL
FIBRILLATION
Speciality: Medical Cardiology
Code: 62720141
ABSTRACT OF MEDICAL PHD THESIS
HA NOI – 2016
Training institution:
MILITARY MEDICAL UNIVERSITY
Instructors:
1. NGUYEN LAN VIET, MD.PHD.Prof.
2. PHAM QUOC KHANH, MD.PHD.
The 1st opponent: Doan Van De, MD.PHD.Prof.
The 2nd opponent: Do Doan Loi, MD.PHD.Prof.
The 3rd opponent: Tran Van Riep, MD.PHD.Prof.
This thesis will be presented at the commission for theses of Military
Medical University
At hours of day month year
This thesis may be found at:
1. The National Library
2. The Library of Military Medical University
3. The Library of Bach mai General Hospital
LIST OF PUBLISHED SCIENTIFIC WORKS
RELATED TO THE THESIS
1. Pham Tran Linh, Pham Quoc Khanh, Nguyen Lan Viet (2015),
"Initial evaluation of the effectiveness of catheter – based radio
frequency ablation of paroxysmal atrial fibrillation", journal of
Vietnamese Medical, 429 (2), pp. 144 150.
2. Pham Tran Linh, Pham Quoc Khanh, Nguyen Lan Viet (2015),
"Clinical manifestations and electrophysiologic features in
patients with paroxysmal atrial fibrillation", journal of
Vietnamese Medical, 430 (1), pp. 159 165.
1
INTRODUCTION
Atrial fibrillation (AF) is one of the most common types of
arrhythmia. AF is associated with a wide range of complications in
clinical practice and may contribute to 5% of stroke cases a year.
Mortality may increase to 34% in patients with heart failure if AF is
concomitant. It is known that AF increases in the prevalence with
advancing age. The incidence of AF is approximately 0.1% in the
patients under 40 years of age while it approaches 1.5 – 2% in the
group over 60 years of age.
It was the first time in 1994 when Haissaguerre utilized the radio
frequency (RF) energy as a therapy for AF patients. Nevertheless,
this method had limitations such as low successful rate of 33 – 60%,
high rate of complications, long procedure time (5 – 6 hours). In
1996, Pappone used a three dimensional mapping system named
CARTO to facilitate the therapy of AF with RF energy. CARTO
system has brought higher efficacy in the treatment of AF as it
guarantees high successful rate and low complication rate. The
system has been upgrading so far to vast the utility in RF ablation of
AF as the most advanced curing method for the disease.
Back to 1998 when RF energy was first settled in Vietnam Heart
Institute – Bach Mai Hospital, then was widespreaded to other heart
centers up and down the country, launching the initiation for the
interventional rhythmology in Vietnam. However, paroxysmal AF
has not been treated with RF energy as a routine procedure in
Vietnam. Some questions have been raised to require the answers.
What are the electrophysiological properties of the paroxysmal AF in
Vietnamese patients ? What are the posibilities to utilize the therapy
and its limitations ? What are the optimal indications for Vietnamese
patients ? What are the early outcomes and the followup results ?
2
In contributing to bring this method into routine practice in
Vietnam, we conduct a research named “Electrophysiological
properties and the efficacy of catheter – based radio frequency
ablation of paroxysmal atrial fibrillation”.
Objectives of our research are:
1. Cardiac electrophysiological properties of paroxysmal
atrial fibrillation patients.
2. Evaluation of shortterm outcomes of radio frequency
ablation of paroxysmal atrial fibrillation.
* Contributions of the research:
Paroxysmal atrial fibrillation often originates from the four
pulmonary veins with 83.3% were from left pulmonary veins
and rarely comes from right atrium.
In episodes of atrial fibrillation, the average AA intervals
were 196.8 ms and VV intervals were 574.4 ms.
Radio frequency ablation of paroxysmal atrial fibrillation has
a high successful rate. Sinus maintenance rate was reached at
88.1% just after procedures and 74.3% after 12 months of
followup. Recurrence rate was 11.4% and complication rate
was 4.7% with no death.
* Structure of the thesis: The thesis consists of 136 pages (not
including appendix and list of references), 50 tables, 10 graphs and
33 figures. There are 132 reference documents, including 12 in
Vietnamese and 120 in English. There are 3 pages for the part of
Introduction, 36 pages for Overview, 21 pages for Object and
Methodology, 33 pages for Research Result, 39 pages for Discussion,
3 pages for Conclusion, 1 page for Suggestion.
3
CHAPTER 1
OVERVIEW
1.1. ELECTROPHYSIOLOGICAL PROPERTIES OF THE LEFT
ATRIUM ANATOMY AND CARDIAC CONDUCTION SYSTEM
1.1.1. Left atrium anatomy: left atrium is bordered by the
pulmonary venoatrial junctions, atrioventricular junction at the
mitral orifice, the left appendage and the septal part.
Left atrium’s walls and atrial septum: left atrium’s walls
include anterior wall, superior wall, free wall (lateral wall), posterior
wall and septal wall.
Atrial muscle: the left atrium consists of three layers:
epicardium, atrial muscle and endocardium. The atrial musculature is
constructed by circumferential and longitudinal muscular bundles.
Those bundles contribute to the formation of pectinate muscles of the
atrium.
Pulmonary veins and ostia: all four pulmonary veins enter the
left atrium at the posterior wall. In most of cases, those pulmonary
veins are separated.
1.1.2. Conduction system:
Sinus node, internodal pathways, atrioventricular node, His
bundle and branches, Purkinje fibers.
1.2. ELECTROPHYSIOLOGICAL PROPERTIES AND CONDUCTION
SYSTEM
Including activation potential, excitability, automaticity,
conductivity and refractoriness.
1.3. PATHOPHYSIOLOGY IN ATRIAL FIBRILLATION
1.3.1. Electrophysiological mechanisms: 3 mechanisms for AF has
been explained:
Single micro reentrant stable circuits.
Frequently macro reentrant unstable circuits.
Single automatic focus firing short interval impulses.
4
1.3.2. Hemodynamic Consequences: hemodynamic consequences
of AF result from multi factors such as loss of atrial contraction,
irregular ventricular response, rapid ventricular rate, coronary
hypoperfusion.
1.3.3. Mechanisms of thrombosis in AF:
Pathophysiology of thrombosis in patients with AF is
complicated. Virchow’s triad contributes 3 factors in leading to
thrombosis: blood stasis, alteration of vessels’ intimal function and
blood hypercoagulability.
1.4. DIAGNOSIS OF ATRIAL FIBRILLATION
1.4.1. Classification of AF based on clinical settings:
Paroxysmal AF: AF that terminates spontaneously or with
intervention within 7 days of onset, commonly within 48 hours.
Persistent AF: AF that sustains over 7 days from onset and be
terminated by pharmacological or directcurrent cardioversion.
Permanent AF: is persistent AF that can not terminate by
pharmacological or directcurrent cardioversion.
1.4.2. Etiology: valvular heart diseases (mitral stenosis or mitral
regurgitation), coronary artery diseases, left ventricular dysfunction,
hypertension, left ventricular hypertrophy, congenital heart diseases
including atrial septal defect, transposition of great vessels …;
hyperthyroidism, idiopathic AF …
1.4.3. Diagnosis: diagnosis of AF bases on routine electrocardiograms.
Some investigations can be doned to diagnose the etiology of AF
including thyroid hormones, echocardiography, chest Xray, stress
test, 24 hour ECG monitoring, event recorder, electrophysiological
study.
1.4.4. Principles of treatment: rhythm control and thrombosis
prevention. Based on the classification of AF, medications,
interventional procedures or other methods can be chosen.
5
1.5. CATHETER – BASED RADIO FREQUENCY ABLATION.
1.5.1. Published international researches:
It was the first time in 1994 when Haissaguerre utilized the radio
frequency (RF) energy as a therapy for AF patients. Nevertheless,
this method had limitations such as low successful rate of 33 – 60%,
high rate of complications, long procedure time (5 – 6 hours). In
1996, Pappone used a three dimensional mapping system named
CARTO to facilitate the therapy of AF with RF energy.
1.5.2. Research in the issue in Vietnam:
It was not until 2009 when the first AF case was ablated using
catheterbased radio frequency.
1.5.3. Patient selection:
Following the 2010 ACC/AHA/ESC Guidelines for
Management of patients with Atrial Fibrillation.
1.5.4. Result of the intervention:
Analysis from the data of 4000 thousand cases in Cleveland
Clinic shows that the successful rate is 80%.
1.5.5. Complications:
Some complications have been reported including vascular
access complications, cardiac perforation, cardiac tamponade,
valvular injury, stroke or TIA, systemic thrombosis, atrialesophagus
fistula, pulmonary vein stenosis ...
CHAPTER 2
OBJECTS AND METHODOLOGY
2.1. OBJECTS
Our research includes 42 patients who were diagnosed
paroxysmal atrial fibrillation and hospitalized from October of 2009
to March of 2014.
2.1.1. Selection Criteria
Following the guidelines of American College of Cardiology,
American Heart Association, European Society of Cardiology
(ACC/AHA/ESC) 2010.
6
Patients were diagnosed symptomatic paroxysmal atrial
fibrillation, with EHRA symptom score ≥ 2, refractory to
pharmacological agents including rate control and rhythm control
(Indication Class IIa, Level of evidence A).
2.1.2. Exclusion Criteria
Severe heart failure (NYHA IV), valvular AF cases that have the
indication for open heart surgery, acute infections, coagulation
disorders, heart chamber thrombus, persistent AF and permanent AF.
2.2. METHODOLOGY
2.2.1. Research design
Cohort study.
2.2.2. Object selection
Objects were selected based on the timeline.
2.2.3. Clinical examination and investigations
All the patients were examined, recorded 12 – lead ECG,
monitored 24 hour ECG recordings. Other investigations were done
before procedures such as blood tests, chest Xray, transthoracic
echocardiography, transesophagus echocardiography, multisliced
CT scanner of left atrium and pulmonary veins.
2.2.4. Electrophysiological study
+ Place of procedures: Laboratory of Catheterization, Vietnam Heart
Institute, Bach Mai Hospital.
+ Equipments:angiography system, stimulator, electrophysiological
recording system, ablation generator, three dimensional mapping
system (CARTO system) and varieties of diagnostic catheters and
ablation catheters.
+Preprocedure preparation: patients were explained about the
purpose, techniques, possible outcomes and complications of the
procedures.
+ Procedure protocol
Placement of catheters
. Diagnostic catheters were placed at the coronary sinus, right
7
atrium, right ventricle, His bundle.
. Mapping catheters and ablation catheters were inserted through
right femoral vein and transseptally to the left atrium.
Electrophysiological protocols
. Electrophysiological properties in sinus rhythm: we measured
PA, AH, HH, HV intevals, QRS duration, QT duration, basic sinus
cycle length.
. Programmed stimulation protocols: rapid atrial pacing, extra
stimulus atrial pacing, rapid ventricular pacing, extra stimulus
ventricular pacing.
Electrophysiological characteristics of Atrial Fibrillation
. Localization of prematured atrial complexes triggering atrial
fibrillation: action potentials were recorded in different regions
within the atrium. Prematured atrial complexes that trigger episodes
of AF were normally recorded earlier than in other regions.
. Measurements of intervals during AF: AA intervals, VV
intervals.
2.2.5. Radio frequency catheter ablation protocol of AF
+ Septal puncture:diagnostic catheters and ablation catheter were
inserted from the right side to the left atrium.
+ A multi electrode catheter (Lasso catheter) were put to record
action potentials inside the ostia of four pulmonary veins.
+ A three dimensional image of the left atrium was created.
+ Pulmonary veins were isolated and other triggering foci of AF in
the left and right atrium were also ablated.
+ Criteria of success:
Cardioversion of sinus rhythm.
No electrical connections were found between left atrial
chamber and the pulmonary veins.
No episodes of AF were inducible during programmed
electrical stimulation.
8
2.2.6. Followup after radio frequency catheter ablation
+ All the patients were monitored at the Cardiac Intensive Care Unit
after the procedures. Parameters such as hemodynamics,
echocardiography, electrocardiograms were obtained.
+ Patients with successful ablations were received antiarrhythmic 3
months after procedures.
+ Followup was carried out with 24 – hour ECG monitoring after 1
month, 3 months, 6 months, 12 months from the procedures.
+ Anticoagulant therapy was also given in 3 months with VKA
targeting INR from 2 to 3, or NOAC.
Study’s protocol
2.3. STATISTICAL ANALYSIS
Statistical analysis was facilitated by software package SPSS
version 17.2 (2007).
9
CHAPTER 3
RESULT
3.1. GENERAL CHARACTERISTICS OF PATIENTS
From October of 2009 to March of 2014, 42 patients with AF
that unresponsive to pharmacological agents were indicated to
undergo radio frequency catheter ablation.
3.1.1. Age and gender
There were 36 male patients (85.7%) and 6 female patients
(14.3%).
Table 3.1. Age and gender
Male (n=36)
Age group
Female (n=6)
Total (n=42)
Number
%
Number
%
Number
%
≤ 50
12
33.
3
2
28.
5
14
32.6
51 60
9
25.
0
2
28.
5
11
25.6
≥ 61
15
41.
7
2
42.
9
17
41.9
3.1.2. Clinical parameters
Table 3.2. Clinical parameters (n=42)
Parameters
Mean
Weight (kg)
64.2 ± 8.8
46 – 80
Height (m)
1.63 ± 0.06
1.50 – 1.74
BMI (kg/m )
24.0 ± 2.2
18.4 – 28.7
Heart rate (bpm)
76.0 ± 13.5
54 – 120
2
10
Systolic pressure (mmHg)
124.6 ± 15.3
100 – 180
Diastolic pressure (mmHg)
78.0 ± 10.2
60 – 100
Table 3.3. Characteristics of AF (n=42)
Index
Number (n=42)
Years from onset
5.0 ± 3.5
Episodes / month
6.9 ± 9.4
EHRA symptom score
%
3.19 ± 0.45
Termination:
Spontaneously
39
90.7
Pharmacological cardioversion
29
67.4
Direct current Cardioversion
4
9.3
Amiodarone
38
88.4
Group IA
8
18.6
Group IC
15
34.9
Group II
11
25.6
Medications:
3.1.5. Twenty four hour ECG monitoring characteristics
Table 3.4. Characteristics of 24hour ECG recordings (n=42)
Index
Average heart rate (bpm)
Total time of bradycardia (< 60 bpm)
Number of episodes of AF
Average duration of AF episodes
Number of PACs
Mean
Range
82.6 ± 13.5
64 – 115
185.2 ± 217.5
0 – 827
9.3 ± 20.9
1 – 107
461.4 ± 590.6
1195.5 ±
1861.6
1 – 1.444
0 – 8.019
11
Couplet PACs
203.1 ± 684.4
0 – 3.850
Triplet PACs
32.7 ± 64.7
0 – 288
Atrial Tachycardia
10.4 ± 399.3
0 – 258
3.2. ELECTROPHYSIOLOGICAL CHARACTERISTICS IN
PATENTS WITH PAROXYSMAL AF
3.2.1. At baseline with sinus rhythm
3.2.1.1. Basic intervals
Table 3.5. Basic intervals
≤ 60 y
> 60 y
(n=25)
(n=17)
Basic cycle
length (ms)
760.2±188.
8
PA intervals
(ms)
Index
P
Overall
886.7±113.
5
0.021
810.8 ± 172.9
21.0 ± 5.1
23.9 ± 5.2
0.124
26.7 ± 8.6
AH intervals
(ms)
91.7 ± 18.3
88.1 ± 12.3
0.092
90.5 ± 15.9
His duration
(ms)
19.0 ± 6.9
18.1 ± 2.9
0.488
18.7 ± 5.6
HV intervals
(ms)
47.4 ± 5.7
48.1 ± 3.9
0.618
47.7 ± 5.0
91.3 ± 11.9
91.2 ± 13.4
0.975
91.3 ± 12.4
389.3 ±
42.2
391.4±29.3
0.834
390.2 ± 30.7
QRS duration
(ms)
QT intervals
(ms)
42 patients were divided into 2 groups based on age. A group
consisted patients ≤ 60 years of age and the other one consisting
12
patients > 60 years of age. The basic cycle length of patients ≤ 60
years of age were significantly shorter than those of > 60 years of
age. There was no significant difference between the
measurements of other intervals.
3.2.1.2. Electrophysiological study of sinus node function
Table 3.6. Sinus node recovery time (SNRT)and corrected sinus
node recovery time (cSNRT) based on age and gender
Index
Male
(n=36)
Gender
Female
(n=6)
≤ 60
(n=25)
Age
> 60
(n=17)
Overall (n=42)
SNRT (ms)
1181.8 ± 201.0
1120.7 ± 170.6
1140.6 ± 190.5
1222.0 ± 200.9
1173.9 ± 196.4
p
0.52
3
0.20
7
cSNRT (ms)
p
310.8 ± 143.2
0.169
403.7 ± 89.2
319.8 ± 114.1
0.881
326.8 ± 174.9
322.7 ± 140.1
There was no significant difference in the SNRT between the
male and female group (p > 0.05). No significant difference was
found between the cSNRT of the patients > 60 years of age and the
patients ≤ 60 years of age.
3.2.1.3. Effective refractory periods (ERP) of the atrium and
ventricle
Table 3.7. ERP of the atrium and ventricle
Index
Atrial ERP
(ms)
Ventricular
ERP (ms)
Atrio
ventricular
dissociation
point (ms)
≤ 60 y (n=25)1
198.7 ± 19.4
218.7 ± 58.7
395.3 ± 21.0
13
> 60 y (n=17)2
215.6 ± 15.9
222.5 ± 15.3
426.3 ± 73.5
Overall (n=42)
205.6 ± 19.7
220.3 ± 17.2
407.9 ± 66.1
P1,2
0.007
0.505
0.001
The atrial ERP and ventricular ERP were within the normal range.
There was no significant difference between two groups of age.
The atrial ERP of the patients ≤ 60 years of age was significantly
shorter than the group of > 60 years of age with p = 0.007.
3.2.2. Electrophysiological characteristics in AF
Atrial programmed electrical stimulations were performed to
induce AF and then action potentials were recorded at different
locations in the left atrium.
3.2.2.1. Locations of PACs triggering episodes of AF
Table 3.8. Locations of PACs triggering AF (n=42)
Location
Number
%
Superior vena cava
2
4.8
Inferior vena cava
0
0
Right atrial isthmus
2
4.8
Left superior PV
35
83.3
Left inferior PV
30
71.4
Right superior PV
33
78.6
Right inferior PV
31
73.8
Right atrium
Left atrium
14
Left appendage
7
16.7
Left atrial isthmus
2
4.8
Over 70% of PACs originated from pulmonary veins, whilst up
to 83.3% of those were from left superior PA.
3.2.2.2. Interval recordings in AF
Table 3.9. Interval recordings based on group of age
Index
Average AA
intervals (ms)
Shortest AA
intervals (ms)
Longest AA
intervals (ms)
Average VV
intervals (ms)
Shortest VV
intervals (ms)
Longest VV
intervals (ms)
≤ 60 y
(n=25)
> 60 y
(n=17)
P
Overall
(n=42)
201.1 ± 35.7
194.7 ± 41.7
0.629
196.8 ± 39.5
135.6 ± 39.4
123.1 ± 29.9
0.261
127.3 ± 33.4
263.1 ± 51.5
249.8 ± 38.1
0.346
254.2 ± 42.9
543.7±104.4
589.8 ±107.8
0.194
574.4 ±107.6
350.0 ± 88.6
415.3 ±102.2
0.049
393.5 ±101.7
813.8±191.5
827.6 ±205.0
0.834
823.0 ±198.4
The role of AV conduction is important in reducing the impulses
travelling from atria to ventricles to maintain tolerant ventricular
response.
3.3. RESULTS OF PAROXYSMAL ATRIAL FIBRILLATION ABLATION
3.3.1. Results of procedures
3.3.1.1. Procedure time
Table 3.10. Procedure time
Index
Overall
(n=42)
Procedure time
288.8 ± 60.4
Other
PV isolation
ablation sites
(n=28)
(n=14)
293.6 ± 58.9
265.0 ± 68.8
P
0.173