Microsoft Word LVTS ENG FINAL docx MINISTRY OF EDUCATION AND TRAINING MINISTRY OF DEFENCE 108 INSTITUTE OF CLINICAL MEDICAL AND PHARMACEUTICAL SCIENCES BY VIEN HOANG LONG MD CLINICAL, PARACLINICAL CHA[.]
LITERATURE OVERVIEW
Diagnosis of atrial fibrillation
Table 1.1: Definition of AF according to ESC AF guideline 2020 [3]
A supraventricular tachyarrhythmia with uncoordinated atrial electrical activation and consequently ineffective atrial contraction
Electrocardiographic characteristics of AF include:
• Irregularly irregular R-R intervals (when atrioventricular conduction is not impaired), • Absence of distinct repeating P waves, and
Symptomatic or asymptomatic AF that is documented by surface ECG
The minimum duration of an ECG tracing of AF required to establish the diagnosis of clinical AF is at least 30 seconds, or entire 12-lead ECG
1.1.2 Diagnostic criteria for atrial fibrillation
Atrial fibrillation (AF) is diagnosed through an ECG that shows an irregular heart rhythm characterized by the absence of distinct P waves and inconsistent R-R intervals A recording lasting 30 seconds or more is considered definitive for clinical AF.
Picture 1.1: AF on 12 lead ECG 1.1.3 Classification of AF
First diagnosed AF not diagnosed before, irrespective of its duration or the presence/severity of AF-related symptoms
Paroxysmal AF that terminates spontaneously or with intervention within 7 days of onset
Persistent AF that is continuously sustained beyond 7 days, including episodes terminated by cardioversion (drugs or electrical cardioversion) after >_7 days
Continuous AF of >12 months’ duration when decided to adopt a rhythm control strategy
Permanent atrial fibrillation (AF) is a condition acknowledged by both the patient and physician, indicating a mutual decision to cease efforts in restoring or maintaining sinus rhythm This designation reflects a therapeutic approach rather than a fundamental characteristic of AF It is important to note that the term "permanent AF" should not be applied when discussing rhythm control strategies involving antiarrhythmic medications or AF ablation If a rhythm control strategy is pursued, the classification of the arrhythmia may change.
Atrial fibrillation management
According to ESC AF guideline 2020, the simple Atrial fibrillation Better Care (ABC) was recommended for AF management
B: Better symptom control (choose rhythm control or rate control strategy)
C: Cardiovascular risk factors and concomitant diseases control
1.2.2 Indications for atrial fibrillation catheter ablation
Table 1.3: HRS/EHRA/ECAS/APHRS/SOLAECE indications for catheter ablation [5]
Class Level of evidence Symptomatic AF refractory or intolerant to at least one Class I or
Paroxysmal: Catheter ablation is recommended
Persistent: Catheter ablation is reasonable
Catheter ablation may be considered
Symptomatic AF prior to initiation of antiarrhythmic therapy with a Class I or III antiarrhythmic medication
Paroxysmal: Catheter ablation is reasonable
Persistent: Catheter ablation is reasonable
Catheter ablation may be considered
In 2020, the European Society of Cardiology issued new guidelines on the indication for catheter ablation of AF These guidelines recommend persistent
AF ablation in symptomatic patients with low risk of recurrence and failure of medical therapy as a class I recommendation [3]
Picture 1.2: ESC guideline for catheter ablation of AF 2020 [3]
Recent studies about atrial fibrillation catheter ablation
1.3.1 Overview of study about atrial fibrillation in Vietnam
AF is a problem that has been concerned and conducted many studies
A study by Tuan N.X (2013) at Hanoi Heart Hospital revealed that arrhythmias are a common complication following cardiac surgery, with atrial fibrillation (AF) occurring most frequently after coronary surgery at a rate of 56.25% In contrast, the incidence of AF was 20.9% after valvular heart surgery and only 9.52% following congenital heart surgery.
A study by Toan N.D, Oanh N.O, and Hieu N.L (2015) revealed that the prevalence of atrial fibrillation (AF) in heart failure patients was 27.2% among 213 participants This rate was notably higher in patients with reduced left ventricular function (ejection fraction < 50%), who also experienced a greater incidence of thromboembolic events, with rates of 8.6% compared to 7.7%.
In a study by Bay N.Q (2015), the effectiveness of medical treatment for atrial fibrillation (AF) in patients with hyperthyroidism was assessed, revealing that 79.2% of the 24 patients with persistent AF experienced spontaneous conversion to sinus rhythm The average time for conversion was 6.6 ± 7.1 weeks, with an impressive 94.7% of patients converting within 17 weeks.
In a study by Dung D.T and Dinh N.H (2017), the outcomes of Cox-Maze IV surgery for treating atrial fibrillation (AF) were analyzed in 41 patients undergoing open-heart surgery The findings revealed a maintenance rate of sinus rhythm of 86% at 3 months, 84% at 6 months, and 84% at 12 months, with only 7.3% of patients needing permanent pacemaker implantation.
Numerous studies have focused on the treatment of atrial fibrillation (AF), particularly in patients with non-valvular AF A notable study by Yen N.T.H (2018) assessed the quality of life changes in these patients before and after catheter ablation The findings revealed a significant improvement in the AFEQT scale, with scores rising from 49.74 ± 13.71 points prior to treatment to 70.60 ± 18.32 points three months post-radiofrequency (RF) treatment, resulting in an average increase of 20.86 points (p < 0.05).
Bach D.D and Hoai N.T.T (2021) conducted a study on left atrial volume and function in atrial fibrillation (AF) patients before and after catheter ablation using 3D-real-time ultrasound They found that the minimum left atrial volume index (LAVI min) significantly increased within 24 hours post-ablation, but gradually decreased at 1 and 3 months, with statistical significance (p 1 year duration): 1 point
Mitral regurgitation severity from mild to severe: 1 point
Extreme comorbidities: 2 points (including conditions like severe mitral regurgitation, moderate to severe mitral stenosis, mitral valve replacement, hypertrophic cardiomyopathy, congenital heart structural abnormalities)
The FLAME score, which ranges from 0 to 9 points, demonstrates a linear correlation with the success of maintaining sinus rhythm after 12 months in patients with persistent atrial fibrillation This relationship was observed in a study involving 361 patients, indicating that the FLAME score is significant for both initial ablation and subsequent interventions.
Table 1.4: Sinus rhythm after 12-month FU according to FLAME score
Sinus rhythm after 1st procedure
Sinus rhythm after final procedure
In addition to the FLAME score, various scoring systems have been explored to predict the likelihood of sustaining sinus rhythm following atrial fibrillation ablation, including the CAAP-AF (2016) and BASE-AF.
HATCH, APPLE, and MB-LATTER scores are scoring systems that evaluate key factors like advanced age, left atrial diameter, duration of atrial fibrillation, and early recurrence of the condition However, there is currently no clinically recommended scoring system to assist in decision-making for atrial fibrillation ablation in patients with persistent atrial fibrillation.
In a study by Verma A et al (2015), additional linear ablation techniques, including roof line, base line, and mitral line, were applied to pulmonary vein isolation (PVI) in patients with persistent atrial fibrillation (AF) However, the findings indicated that the success rate for sustaining sinus rhythm after 19 months was not statistically significant when compared to treatment with PVI alone.
- He X., Zhou Y and Chen Y (2016) made a meta-analysis to compare the effectiveness of posterior box isolation add on to PVI and PVI-only treatment and had negative result [22]
- Kottkamp H et al (2016) made a trial to add on low - voltage zone ablation to PVI and slightly increased success rate after 1 year from 69.2% to 72.2% [23]
- Stavakis S et al (2015) added ganglionated plexi (GP) to PVI for persistent AF patients but had success rate after 1 year was only 60% [24].
SUBJECTS AND METHODS
Subjects
A total of 40 patients were diagnosed with persistent atrial fibrillation (AF) All patients underwent catheter ablation for AF in Vietnam National Heart Institute, Bach Mai Hospital from October 2017 to November 2021
- Persistent AF lasts beyond 7 days, including episodes terminated by drugs or electric cardioversion after ≥7 days (based on history and ECG)
The 2016 European Society of Cardiology (ESC) guidelines and the Vietnam National Heart Association/Vietnam Heart Rhythm Society recommend catheter ablation for atrial fibrillation (AF), categorized as Class IIa with a level of evidence C.
● Symptomatic AF patients failed or intolerant to class I or class III antiarrhythmic drugs
● Symptomatic AF patients made the choice of catheter ablation after discussing about rhythm control strategy of atrial fibrillation catheter ablation and antiarrhythmic drugs
Table 2.1: European Heart Rhythm Association (EHRA) symptom scale [25]
1 None AF does not cause any symptoms
2a Mild Normal daily activity not affected by symptoms related to AF
2b Moderate Normal daily activity not affected by symptoms related to AF, but patient troubled by symptoms
3 Severe Normal daily activity affected by symptoms related to AF
4 Disabling Normal daily activity discontinued
- Very elderly patients (>80 years old)
- Paroxysmal AF and permanent AF
- Heart failure with reduced or mildly reduced ejection fraction (EF ≤49%)
- Indications for cardiac valve surgery, coronary revascularization
- Mental or physical inability to take part in the study
2.1.3 Diagnostic criteria used in the study
- Diagnostic criteria for AF on standard 12-lead electrocardiography (ECG) and 24-hour ECG Holter monitoring: Absence of distinct P waves, f wave may be presented (atrial rate 400-600 beats/min), irregularly irregular R-
R intervals An episode of AF, which continuously sustained ≥30 seconds on ECG Holter monitoring, is considered as AF recurrent
In this study, we measured the diameters of pulmonary vein ostia using multisided computed tomography (MSCT) at the points where each pulmonary vein drains into the left atrium.
- Left atrial size: is measured on two-dimensional echocardiography at apical 4-chamber view and MSCT visualization of pulmonary veins and left atrium
Arterial hypertension is characterized by a consistent increase in blood pressure, defined as systolic blood pressure of 140 mmHg or higher and/or diastolic blood pressure of 90 mmHg or higher This condition may occur despite treatment with antihypertensive medications or a prior history of hypertension, as outlined in the 2018 ESC guidelines for arterial hypertension.
- Diabetes: 2017 American Diabetes Association criteria for the diagnosis of diabetes [27]:
● HbA1C ≥6.5% The test should be performed in a laboratory using a method that is NGSP certified and standardized to the DCCT assay *OR
● FPG ≥126 mg/dL (7 mmol/L) Fasting is defined as no caloric intake for at least 8 hours *OR
A 2-hour plasma glucose level of 200 mg/dL (11.1 mmol/L) or higher during an Oral Glucose Tolerance Test (OGTT) indicates potential diabetes This test should be conducted following the World Health Organization's guidelines, utilizing a glucose solution that contains 75 g of anhydrous glucose dissolved in water.
● In a patient with classic symptoms of hyperglycaemia or hyperglycaemic crisis, a random plasma glucose ≥200 mg/dL (11.1 mmol/L)
HbA1C: glycated haemoglobin; NGSP: National Glycohemoglobin Standardization Program; DCCT: Diabetes Control and Complications Trial; FPG: fasting plasma glucose; OGTT: oral glucose tolerance test
* In the absence of unequivocal hyperglycaemia, diagnosis requires two abnormal test results from the same sample or in two separate test samples
- Excessive alcohol use (U.S CDC guidance): Including:
● Binge drinking, defined as consuming 4 or more drinks on an occasion for a woman or 5 or more drinks on an occasion for a man
● Heavy drinking, defined as 8 or more drinks per week for a woman or 15 or more drinks per week for a man
- Electrophysiology study: Comparing the normal preferences of electrophysiological values of Vietnamese adults, which are the results of a study by Pham Quoc Khanh et al in 2005
● Evaluation of sinus node function: Determination of sinus node recovery time (SNRT) and corrected sinus node recovery time (cSNRT)
Picture 2.1 Evaluation of sinus node recovery time [28]
The end of a 30-second pacing train with cycle length of 700ms, and the resumption of sinus rhythm The SNRT (last S1 to first A) is 1175 ms
● Evaluation of conduction over the AV node: Antegrade and retrograde
Wenckebach point, the effective refractory period (ERP) of antegrade and retrograde AV nodal conduction.
Methods
- Sample size: All patients met the inclusion and exclusion criteria from October 2017 to November 2021
Upon admission, each patient underwent a medical history review and physical examination All information were recorded in “Study record” (Supplementary material 1):
● The first time when patient was diagnosed AF and the treatment was given
● Score of EHRA symptom scale
● Cardiovascular examinations: heart rate, heart murmur
● Height, weight and body mass index (BMI)
- Basic blood tests: complete blood count, sedimentation rate, coagulation test, blood glucose, electrolyte panel, urea, creatinine, transaminase, FT4, TSH
- Standard 12-lead ECG by Nihon Kohden ECG machine
- Transthoracic echocardiography: cardiac size and function, heart valve
- Transoesophageal echocardiography: intracardiac thrombus, anomalous pulmonary vein drainage
- MSCT visualization of pulmonary veins and left atrium: facilitating for 3D endocardial mapping precisely
Coronary angiography can be conducted using multi-slice computed tomography (MSCT) with 64 or more slices, or through transcutaneous coronary artery imaging for high-risk patients, specifically males aged 40 and older and postmenopausal females This approach aligns with the preoperative risk assessment guidelines established by the ACC/AHA in 2014 (Class I-C).
2.2.2.3 AF ablation and electrophysiology study a Location
Catheterization Lab, Vietnam National Heart Association, Bach Mai Hospital b Pre procedure preparation
- Check the necessary tests for the procedure
- Patient signs the informed consent c Equipment
- Angiography system: Philips Allura Xper FD20 biplane angiography system (Dutch)
- The electrophysiological study system: St Jude Medical EP-4 Cardiac Stimulator and St Jude electrophysiological recording system
Picture 2.3 Cardiac Stimulator (a), Electrophysiology System (b) and RF
- The radiofrequency generator: St Jude Medical Ampere RF Ablation Generator
The irrigation pump is designed to work seamlessly with the St Jude irrigated-tip ablation catheter for effective temperature control It can function either independently or in conjunction with the RF generator, offering versatile operational modes Additionally, the pump supports a customizable flow rate to meet specific procedural requirements.
The Ensite Velocity 3D cardiac mapping system offers advanced 3D visualization for intracardiac anatomical mapping, integrating activation mapping and intracardiac impedance This innovative technology aids in diagnosing arrhythmia mechanisms and pinpointing the most effective ablation sites.
Picture 2.4 3D Ensite system and the locations of electrode patches
- Diagnostic electrode catheters: Biotronik and St Jude manufactures
● 5F or 6F, 5-mm spaced quadripolar catheter, placed in the right ventricular apex
● 5F or 6F, 2-8-2-mm spaced decapolar catheter, placed in the coronary sinus
- The decapolar circular mapping catheter (PV electrode): can be controlled flexibly and collect electrical signals from pulmonary veins The distance between two consecutive electrodes is 2 mm
Picture 2.5 The steerable, decapolar circular mapping catheter
The Thermocool catheter is a 7 Fr, 3.5 mm deflectable ablation catheter designed for endocardial mapping and radiofrequency ablation Its irrigated tip enhances lesion depth and size while minimizing damage to adjacent tissues.
Picture 2.6 The irrigated tip ablation catheter d Technique protocol
- The sites of puncture (left femoral vein, right left femoral vein, left subclavian vein) are subcutaneously anaesthetised with Lidocaine
- The coronary sinus electrode catheter is often inserted through the left subclavian venous 6 Fr sheath
- Right ventricular and right atrial electrode catheters are inserted through the left femoral venous 6Fr sheath
● Right ventricular electrode catheter is often placed at the right ventricular apex
● The right atrial electrode catheter is placed at the high right atrium, near the position of the sinus node, or placed in the right atrial appendage
Two 8Fr long sheaths (SL0) are introduced via the right femoral vein to facilitate transseptal puncture, allowing for the advancement of the ablation catheter and pulmonary vein loop electrode into the left atrium.
- The invasive blood pressure is continuously monitored during the procedure via a 5Fr femoral arterial sheath
- During the intervention, the patient is undergoing general anaesthesia by continuous intravenous infusion of Fentanyl at a dose ranging from 250 to 500 micrograms per hour
Picture 2.7 (a) The left subclavian venous access for placement of coronary sinus electrode catheter, (b) The right femoral venous accesses for two long sheaths and the left femoral venous access for placement of right ventricular electrode catheter
Transseptal puncture is a crucial step in the atrial fibrillation (AF) ablation procedure It begins with advancing a 0.035’’ guidewire under fluoroscopic guidance from the femoral vein to the superior vena cava (SVC) A long sheath is then advanced over the guidewire to the SVC, positioned above the cavo-atrial junction After removing the guidewire, a Brocken Brough needle is inserted into the long sheath and gently advanced to its tip Both the needle and sheath are then pulled back to the target site for the puncture, with the needle advanced beyond the sheath tip while keeping the sheath in place Once the sheath is positioned in the left atrium, the needle is retrieved For safety, left atrial pressure should be confirmed with contrast before advancing the long sheath, and heparin is administered post-puncture, typically at a dose of 5000 IU.
Picture 2.8: Sheath 6F, long sheath SLO, septal puncture needle
In our study, we perform the transseptal puncture once, allowing the insertion of the ablation catheter into the left atrium via a long sheath A second long sheath is then advanced to the left atrium through the transseptal puncture site, guided by fluoroscopy Following the puncture, we conduct left atrial imaging by injecting contrast medium through the long sheath while pacing the right ventricle at a rate of 200 to 220 beats per minute.
Picture 2.9 The right ventricle is stimulated and the left atrial imaging is performed in LAO 30º view (a) and RAO 30º view (b) 3D reconstruction of the left atrium and voltage mapping
The Ensite Velocity System effectively transforms voltage signals into detailed 3D models of the heart By positioning the PV electrode within the pulmonary veins, left atrial appendage ostium, and mitral annulus, it reconstructs an accurate 3D representation of the left atrium.
*Localization and pulmonary vein isolation ablation
In a 3D model of the left atrium, the pulmonary venous ostia were identified, followed by radiofrequency ablation targeting the electrical potentials around the pairs of pulmonary veins on both sides.
During the procedure, the patient receives pre-anaesthesia and intravenous heparin to achieve an activated clotting time of 250 to 300 seconds, while continuous temperature monitoring is performed in the left atrium An irrigation-tip catheter is utilized, applying a power of 30-35W to the anterior aspect of the pulmonary veins (PVs) and 25W to the posterior aspect and roof of the PVs Successful pulmonary vein isolation is indicated by the absence of electrical signal connections between the PVs and the left atrium.
*Electrical cardioversion to sinus rhythm
Following pulmonary vein isolation, if atrial fibrillation persists, electrical cardioversion to restore sinus rhythm is necessary Intravenous propofol can be administered quickly, and a synchronous shock of 200J may be applied Once sinus rhythm is achieved, it is essential to evaluate the completeness of the pulmonary vein isolation.
- No electrical signal is recorded when the circular PV electrode is placed in the PVs
Picture 2.10 Elimination of all the potentials in the PVs (a) Pulmonary venous electrical signals before ablation; (b) Pulmonary venous electrical signals after ablation [30]
- Failure to conduct into PVs when pacing in the left atrium (the coronary sinus electrode can be paced with an amplitude of 10 mV and a pulse width of 2.0 ms)
Picture 2.11 The atrium is captured when pacing from the coronary sinus electrode, but no conduction into the PV (no electrical signal is recorded from the PV electrode placed inside the left superior pulmonary vein)
- Failure to conduct into the left atrium when pacing from the PVs (using the circular PV electrode with an amplitude of 10 mV and a pulse width of 1.0 ms)
Picture 2.12 No conduction into the left atrium when pacing from the PV1-
*Assessment for non-PV triggers and additional ablation according to HRS guidelines 2017
- Additional ablation of non-PV atrial ectopic foci may be performed if present after cardioversion to sinus rhythm (IIa-C)
Additional ablation for typical atrial flutter may be conducted if a patient is diagnosed with typical atrial flutter through ECG or Holter ECG monitoring, or if typical atrial flutter is induced during atrial fibrillation (AF) ablation.
- Additional ablation of low voltage areas in left atrium if present (IIb-B)
*Identification of low voltage zone
Following electrical cardioversion to achieve sinus rhythm, the Ensite Velocity system can facilitate peak-to-peak voltage mapping by establishing an upper limit of 0.5 mV and a lower limit of 0.2 mV The voltage of a sinus beat serves as the baseline, allowing for effective voltage mapping to be conducted.
Study data analysis
Data analysis was conducted using SPSS 20.0 and STATA 17.0 to determine experimental mean, variance, and standard deviation The independent samples T-test compared two independent means, while the paired-samples T-test assessed the means of two variables within the same group ANOVA was employed to analyze differences among three or more groups, and the Cox regression model identified the linear correlation of risk factors A p-value of less than 0.05 was deemed statistically significant.
Study ethics
Before ablation, patients and their legal representatives received a thorough explanation of the potential risks and complications associated with the procedure They were required to sign an informed consent form to confirm their understanding of these risks The AF ablation was conducted in accordance with the "Guidance for Cardiovascular Technique Procedures" issued by the Ministry of Health in 2014.
RESULTS
General characteristics of the study group
Between October 2017 and November 2021, we gathered data on 40 symptomatic persistent atrial fibrillation patients who underwent catheter ablation utilizing a 3D mapping system at the Vietnam National Heart Institute - Bach Mai Hospital The results of this study are presented below.
Amiodarone use before ablation (n, %) 40 cases (100%)
Beta-blockers use before ablation (n, %) 10 cases (25%)
All patients used amiodarone before hospitalisation with dose 100 - 200mg/day There were 4 patients used both Beta-blockers and amiodarone
80% of patients in the study were male, 20% of patients were female
In our study, individuals aged 60 years and older represented the largest demographic at 40%, while those under 50 and those between 50 and 59 each accounted for 30% The average age of participants was 54.25 years, with a standard deviation of 12.54 years.
72 years old and the youngest patient is 23 years old
Table 3.2 Sex and age subgroups distribution
Our study population consisted predominantly of males, with fairly equal distribution across three age groups: 30 premature atrial contractions per hour or with episodes of non-sustained atrial tachycardia ≥20 beats per minute had a 2.87-fold increased risk of developing AF and a 2.79-fold increased risk of recurrent stroke, even after adjusting for multiple factors Furthermore, the risk of all-cause mortality or stroke-related death increased by 1.64-fold and 1.4-fold, respectively, even after adjusting for multiple factors [77] Bertaglia (2005) conducted a study to evaluate the predictive value of early recurrence of atrial arrhythmias following pulmonary vein isolation on the success rate of maintaining sinus rhythm in
143 patients followed for 18.7±7.2 months The author noted that ATs within
Ablation success rates for maintaining sinus rhythm were notably lower in patients experiencing early atrial arrhythmias (22% within 48 hours) compared to those free of atrial arrhythmias (43% vs 95%, p