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LITHUANIAN UNIVERSITY OF HEALTH SCIENCES
USE OF INTRACARDIAC ECHOCARDIOGRAPHY FOR ATRIAL FLUTTER ABLATION
Master’s Thesis
Eitan Chiko
Supervisor: Prof. Tomas Kazakevičius
MEDICAL ACADEMY FACULTY OF MEDICINE DEPARTMENT OF CARDIOLOGY
2 TABLE OF CONTENTS
1. SUMMARY ... 4
2. ACKNOWLEDGEMENTS ... 6
3. CONFLICT OF INTEREST ... 7
4. CLEARANCE ISSUED BY THE ETHICS COMMITTEE ... 8
5. LIST OF ABBREVIATIONS ... 9
6. LIST OF TERMS……….10
7. INTRODUCTION………11
8. RESEARCH METHODOLOGY ... 12
9. AIM AND OBJECTIVES ... 14
10. LITERATURE REVIEW………..15
10.1 CTI-DEPENDANT ATRIAL FLUTTER………...15
10.2 PROCEDURAL OVERVIEW………16
10.3 CAVO-TRICUSPID ISTHMUS ANATOMICAL PROPERTIES EVALUATION AND ITS RELATION TO ATRIAL FLUTTER ABLATION………..17
10.4 RADIATION EXPOSURE……….20
10.5 ASSESSMENT OF LEFT ATRIAL THROMBUS FORMATION, OR SPONTANEOUS CONTRAST PRESENCE PRIOR TO ATRIAL FLUTTER ABLATION PROCEDURE………21
10.6 LIMITATIONS OF INTRACARDIAC ECHOCARDIOGRAPHY………..25
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4 1. SUMMARY
Master thesis authored by Eitan Chiko.
Title: Use of Intracardiac Echocardiography for Atrial Flutter Ablation
Aim:
The aim of the study is to evaluate the usefulness and efficacy of intracardiac echocardiography for atrial flutter ablation
Objectives:
1. Determine the possibility of evaluation of cavotricuspid anatomical properties
2. Assessment of left atrial thrombus formation, or spontaneous contrast presence prior to the atrial flutter ablation procedure
Methodology: A systematic literature review was carried out through PubMed, and Wiley Online Library electronic databases. The search parameters included the keywords: intracardiac echocardiography, cavotricuspid isthmus, atrial flutter ablation, thrombus identification, left atrial appendage, spontaneous echo contrast. The overall database search result yielded 2013 articles of which 41 were reviewed after an inclusion criteria screening was performed, taking into consideration the relevance of the articles to the encompassing aim and objective of this study, as well as the period of those publications, that would not exceed a time frame going back ten years. After the initial screen and review, a total of 23 articles were chosen to be the foundational bases of the review.
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radiation, compared with fluoroscopic investigations, does not require anesthesia, and overall shortens the procedural duration and RFA time and exposure.
Recommendations: The current scarcity of studies on ICE employment for Afl ablation
6 2. ACKNOWLEDGEMENTS
7 3. CONFLICT OF INTEREST
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4. CLEARANCE ISSUED BY THE ETHICS COMMITTEE
9 5. LIST OF ABBREVIATIONS
ICE – Intracardiac Echocardiography LAA – Left Atrial Appendage
LA – Left Atrium RA – Right Atrium
RFA– Radiofrequency Ablation CS– Coronary sinus
CTI– Cavotricuspid Isthmus Afl – Atrial Flutter
Afib – Atrial Fibrillation
TEE- Trans-Esophageal Echocardiography TSP- Trans-septal Puncture
10 6. LIST OF TERMS
Cavotricuspid isthmus (CTI) – An area located in the lower section of the right atrium, demarcated by the inferior vena cava and the tricuspid valve. It is has been shown to play a significant role in the development of CTI-dependent atrial flutter due to the characteristic ability to instigate conduction delay and a macro reentrant circuit. It has been shown to exhibit many anatomical variations in individuals, a fact which impacts the ability to perform targeted ablative procedures in this area and ultimately affects the process of interventional methods and outcomes. [1, 2, 3, 6]
Left Atrial Appendage (LAA) – Remnant of the embryonic LA. Its exact function is still unclear, but it has been known to be a site of thrombus formation(thought to be due to its structure, generating various flow pattern), thus, in interventional procedures involving Afl ablation is of the utmost importance to be evaluated prior to the procedure.[7]
Trans-septal Puncture (TSP) - A process required to gain access to the LA, commonly used for left-sided interventions involving Afib ablation, and usually done in the area of the oval fossa. TSP has been known to be a critical moment in interventional procedures which may cause intra-operative thrombus formation or tissue injury leading to procedural complications, as shown by some studies which found real-time SEC occurrence at the moment of puncture.
11 7. INTRODUCTION
Atrial flutter is quite a common type of arrhythmia with an “incidence rate of 88/100,000 persons/years” (1) with the most prominent type being a CTI dependent flutter. [1]
Catheter ablation procedures are considered safe and very effective in rhythm restoration and prevention of complications such as stroke and embolization, where pharmacological therapeutic interventions are lacking.
Notwithstanding the usage of anticoagulation regimens in patients with atrial flutter, thrombotic complications persist.
During the ablation procedure of atrial flutter, restoration of sinus rhythm is achieved, and the first electromechanical contraction of the left appendage may result in the release of such thrombi to peripheral vessels, causing embolization.
Additional intraoperative investigation with intracardiac echocardiography may reduce the risk of thromboembolic complications during interventional procedures.
12 8. RESEARCH METHODOLOGY
The review was carried out by acquiring relevant data pertaining to the study aim and objectives through PubMed, and Wiley Online Library electronic databases.
Intracardiac echocardiography, cavotricuspid isthmus, atrial flutter ablation, thrombus identification, management, let atrial appendage, spontaneous echo contrast.
Time period: 2011-2021
The overall search yielded a total of 2013 articles, of which 122 were further reviewed after the application of a publication date filter and duplicate results from both databases. Of those, I selected a total of 41 for in-depth analysis, and ultimately 23 of which were analyzed for the purpose of establishing the foundational element of the review results and conclusions.
The selection process included several parameters, designed to encompass relevant clinical data and trials that would prove beneficial in presenting a clear picture with regards to the application of ICE in Afl ablation procedures.
At first, I reviewed the abstract of those articles, trying to identify whether the underlying premise of those held significant contributions to the study objective and if so to what extent. Following this notion, I analyzed and extracted the relevant information and results to establish my conclusions.
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Due to the apparent scarcity of information that specifically refers to Afl ablation using ICE, I have decided to include Afib interventional procedures as more information existed on the topic, and have a direct correlation to my thesis objectives.
Figure 1- PRISMA based flow diagram for systematic reviews
Records identified from: Databases (n = 2) Registers (n = 2013)
Records removed before the
screening:
Duplicate records removed /Records removed for other reasons (n =1891) Records screened (n = 122) Records excluded (n = 81)
Reports sought for retrieval (n = 41)
Reports not retrieved (n = 0)
Reports assessed for eligibility (n = 41)
Reports excluded: (n= 0)
Studies included in the review (n = 41)
Identification
Screening
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9. AIM AND OBJECTIVES
Aim of the study: The aim of the study is to evaluate the usefulness and efficacy of intracardiac echocardiography for atrial flutter ablation
Objectives:
1. Determine the possibility of evaluation of cavotricuspid anatomical properties
15 10. LITERATURE REVIEW
10.1 CTI-dependent atrial flutter- This type of Afl is also referred to as “typical” and is the most common type of flutter in occurrence. The flutter is generated when a re-entrant circuit is present within the RA, which passively activates the LA as well. The course of the circuit runs across the CTI, located between the IVC and the tricuspid valve, and has long been established as the primary ablative target for the resolution of Afl. The re-entrant circuit may occur, either in a CCW manner (when the current descends in the lateral aspect of the RA wall and ascends on the RA septum, leading to passive activation of the LA) or in a Clockwise manner (when the current descends in the RA septal aspect and ascends on the lateral wall of the RA). In both cases, the CTI remains the pivotal point of crossing, a contributing factor to the fact why it is the location of ablation target during ICE intervention for Afl management.
The use of ICE can be beneficial in applying a mapping catheter to distinguish these types of Afl but commonly ECG is used before the ablation procedure to determine their presence. [2, 3]
Figure 2-Typical counterclockwise atrial flutter with variable atrioventricular transmission and alternating right and left bundle branch block.
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Figure 3- Clockwise cavotricuspid isthmus dependent atrial flutter with 4:1 atrioventricular conduction and a complete right bundle branch block. It may be difficult to characterize the presence of positive flutter waves in the inferior leads, but the plateau phase is obviously shortened. The negativity of the flutter waves is also difficult to interpret in lead V1.
Bun SS, Lațcu DG, Wedn AM, Hasni K, Saoudi N. Cavotricuspid isthmus-dependent atrial flutter: clinical perspectives. Research Reports in Clinical Cardiology. 2019;10:7-17 [3]
10.2 Procedural overview – The procedure requires femoral access, through which a catheter is guided towards the RA, the most prominent of which for these types of procedures is the
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able to alert the operator when tissue contact is present. Following the RFA, the procedure is considered to be successful when arrhythmia is terminated or in the case of CTI Afl, a bidirectional block is achieved. [4, 1]
10.3 Cavo-tricuspid Isthmus anatomical properties evaluation and its relation to atrial flutter ablation – As mentioned previously CTI dependent Afl is a very common type of Afl, this type of flutter is very susceptible to ICE ablation and accounts for most EP interventions.
Although the ICE guided ablation procedure has a high success rate, low recurrence rate, and is often curative still may pose a great challenge in the management of Afl. The main reason thought to be the leading element to this challenge is the preexisting variation between different patients with regards to its complex anatomical features. These anatomical features include the ER depth, CTI length, and morphological features (presence of pouches, distinct concave or straight CTI orientation). All these may arise as potential barriers or points of impedance to achieve bi-directional block during the ablation procedure.
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Figure 4-A representative case in which a pouch was identified by both angiography (a yellow arrow) and ICE (b yellow arrow). CS coronary sinus, ICE intracardiac
echocardiography, IVC inferior vena cava, RA right atrium, RAO right oblique view, RV right ventricle, SVC superior vena cava, TV tricuspid valve
Hisazaki K, Kaseno K, Miyazaki S, Amaya N, Hasegawa K, Shiomi Y, Tama N, Ikeda H, Fukuoka Y, Morishita T, Ishida K, Uzui H, Tada H. Intra-procedural evaluation of the cavotricuspid isthmus anatomy with different techniques: comparison of angiography and intracardiac echocardiography. Heart Vessels. 2019 Oct;34(10):1703-1709 [20]
Number of patients, n (%) Procedure time, min Total RF time, s Total RF energy, J
19 Number of patients, n (%) Procedure time, min Total RF time, s Total RF energy, J Ridge Ridge ( + ) 46 (50) 13.2 ± 9.1 441.1 ± 205.9 17,684 ± 18,463.7 Ridge (−) 46 (50) 12.6 ± 4.9 452.9 ± 199.0 14,258 ± 6345.6 p-value 0.68 0.78 0.24
Table 1- Association between CTI anatomy and procedural parameters
Hisazaki K, Kaseno K, Miyazaki S, Amaya N, Hasegawa K, Shiomi Y, Tama N, Ikeda H, Fukuoka Y, Morishita T, Ishida K, Uzui H, Tada H. Intra-procedural evaluation of the cavotricuspid isthmus anatomy with different techniques: comparison of angiography and intracardiac echocardiography. Heart Vessels. 2019 Oct;34(10):1703-1709[20]
The resultant study demonstrated the efficacy of using ICE guided survey of the different anatomical features of the CTI, and their implication towards procedural variation as well as concluded the benefit of ICE over angiography taking into account the visualization advantage of all anatomical structures that were not identified through angiography. “On the angiographic evaluation, a pouch was detected in 22 patients but was not identified in the remaining eight patients among the 30 patients in whom a pouch was identified on ICE imaging” [20]
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Figure 5-(A) Uncommonly muscular isthmus showing active contractions. The pouch is deep (17 mm), wide, and is covered partially by the EVR. The ablation catheter was navigated by the ICE to stabilize the tip on both structures and achieve a conduction block. (B) CTI with a muscular bundle on the ventricular side and a deep and narrow pouch on the atrial side of the isthmus. Targeted ablation of both structures was needed to establish a block on the isthmus. (C)
ICE‐image of a unique case where RFA of the muscular EVR (capable of electrical conduction) was performed from the venous side to complete the block on the CTI. Arrow: ablation catheter. EVR: Eustachian‐valve/ridge. P =pouch; TV= tricuspid valve; M= muscular bundle; RCA = right coronary artery.
BENCSIK, G., PAP, R., MAKAI, A., KLAUSZ, G., CHADAIDE, S., TRAYKOV, V., FORSTER, T., and SÁGHY, L. (2012), Randomized Trial of Intracardiac Echocardiography During Cavotricuspid Isthmus Ablation. Journal of Cardiovascular Electrophysiology, 23: 996-1000[12]
“From the 52 patients randomized to the fluoroscopy-only group, 7 patients (13.45%) crossed over to an ICE-guided procedure because of prolonged RF ablation and/or fluoroscopy times (1331.42 ± 604.09 seconds and 29.00 ± 13.22minutes, respectively). All of them were successfully treated with ICE-guidance” [12]
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swelling and changes in density subsequent to RFA causing more difficulties in achieving a bi-directional block and Afl management [12]
10.4 Radiation exposure– As previously mentioned, the use of ICE may reduce the overall procedure time, diminishing the radiation exposure and in many cases rendering it obsolete. It has been well established that radiation exposure, both to patient and operator, holds potential risks associated with the manifestation of cancerous and tissue-altering processes. Although specific data is lacking with regards to specific exposure periods and the amount of radiation contributing to such processes, this exposure should be mitigated to the furthest extent possible. As ICE is being applied more often for interventional procedures it may present as a more viable solution in cases where fluoroscopy can be avoided altogether, rather than being a complementary tool for more difficult scenarios where its use is necessitated. [22, 30]
10.5 Assessment of left atrial thrombus formation, or spontaneous contrast presence prior to the atrial flutter ablation procedure
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exclusion of their presence. Due to the risk associated with thrombosis, ablation procedures are contra-indicated when found to occur within the left atrium. [7]
TEE is still considered the gold standard for identifying thrombus formation within the LA and LAA, throughout the years it has been a standard practice with high success rates in findings indicating the presence of thrombi, although on occasion they yielded false-negative results and complications arose during or after the interventional procedure. Due to this fact, ICE was first introduced as a complementary tool early on for LAA visualization and to confirm the presence of thrombus when TEE results were inconclusive in a specific patient. Furthermore, several
prerequisites for the employment of TEE exist which may not suit all patients and require different approaches. During TEE the patient needs to undergo anesthesia, this adds another element of discomfort, risk management, and additional personal to monitor the status during the procedure. For some patients, TEE is not possible due to the physical limitation of inserting a probe through the patient’s esophagus in the presence of various pathological processes. [7, 12]
In the review of currently available data and clinical studies, the use of ICE for the purpose of thrombus identification prior to exclusively atrial flutter ablation was not present, but rather before Afib ablation. This is of important note, even though the mechanism and complications are
essentially similar in both cases, in left-sided interventions, such as Afib ablation a key maneuver known as a TSP is performed, this is a focal point for thrombosis formation and intraoperative complications arising. An important distinction must be made as in previous studies, the formation of thrombi in real-time during a TSP is well visualized using ICE, and the presence of spontaneous contrast is well seen at the moment of the puncture itself. In this review the main objective is to examine possibilities of detection before Afl ablation, the reference studies are all with relation to Afib ablation and due to the previously mentioned important distinction, it will refer only to the identification of thrombi presence and visualization of the LA and LAA and not the outcomes of the ablation procedure itself.[7]
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equivocal, or when TEE was not possible. The first study involved a group of 76 patients who underwent TEE for evaluation of a thrombus presence, followed by an ICE for the same purpose. The echocardiographer and electrophysiologist who analyzed the ICE results were blinded to the finding of the TEE, this ensured unbiased evaluation. The research also sought to determine the optimal location for placement of the ICE probe, as to receive the best quality images of the LAA, for this purpose two probes were placed, one in the PA and one within the CS. [16]
The study results with regards to the presence of thrombi showed no superiority of one method over the other, a thrombus of the LAA was found in the same two patients who underwent TEE and ICE. Regarding the LAA visualization with ICE, the results have that positioning of the probe within the PA allows for better LAA assessment when comparing to positioning within the CS, which correlated very well with the findings on TEE.[16]
“In those patients in whom the LAA was clearly visualized by ICE from the PA, an excellent agreement between TEE and ICE was obtained. Of these 56 patients, 43 subjects had grade 5 on ICE and the remaining 13 had grade 4. In 13 patients, visualization of the LAA from the CS had a perfect agreement with TEE: 5 patients had grade 5 on ICE and the remaining 8 had grade 4. The mean time for achieving a satisfactory image of the LAA from the PA was 4-/+4.5 minutes and from the CS was 4.2+/- 3 minutes (non-significant [NS])” [16]
The grading scale of obtained images is as follows:
Grade 4(good)- the entire LAA was imaged but the quality was <5 Grade 5(excellent) - the entire LAA was imaged
It is important to note that 2 of the participants were excluded from the study due to their inability to undergo TEE (one due to esophageal varices, and the other due to inability to swallow the probe during TEE).[16]
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included and ICE was performed 24h after the TEE procedure. The thrombi features were differentiated based on their echogenicity properties. [17]
“On TEE, in 7 (33%) patients a solid thrombus was detected, and in the remaining 14 (67%) patients there was a soft thrombus. Disagreement between TEE and ICE was found in 9 (43%) patients (thrombus in TEE and no thrombus in ICE). In the solid thrombus group, ICE confirmed thrombus existence in 6 (86%) patients and excluded thrombus in 1 (14%) patient. In the soft thrombus group, ICE confirmed a thrombus in 6 (43%) patients and excluded it in the remaining 8 (57%) patients.”[17]
Once more the study demonstrated the value of using ICE additionally for detection of LAA thrombi, with additional characterization in cases when a soft thrombus was suspected during TEE.
Figure 6-Examples of LAA visualization. Patient with a thrombus (arrow) in the LAA in the TEE examination (A) and without in the ICE examination (B). (C, D) Projection of the thrombus in the LAA in both visualization modalities—TEE and ICE—in the same patient. Abbreviations: ICE, intracardiac echocardiography; LAA, left atrial appendage; TEE, transesophageal
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Baran J, Zaborska B, Piotrowski R, Sikora-Frąc M, Pilichowska-Paszkiet E, Kułakowski P. Intracardiac echocardiography for verification for left atrial appendage thrombus presence detected by transesophageal echocardiography: the ActionICE II study. Clin Cardiol. 2017;40(7):450-454 [17]
One earlier study performed in 2012, revolving around a similar premise of ICE application for LAA assessment for the presence of thrombi when TEE yields equivocal findings supported the claim the ICE should be employed in those cases. It stated the favorable conditions for it relying on the ability to provide serial real-time imaging of the LAA anatomy and the ability to assess spontaneous contrast and sluggish flow in addition to verify the presence of thrombi.[11,18]
SEC, being an important predictive factor in the evolution of thrombi and thrombotic
complications holds significant bearing on various techniques used in patients before ablative procedures. [5, 11]
One study performed, in addition to comparing the capabilities of both TEE and ICE in LAA and RA evaluation for detection of thrombus, separately investigated the ability to distinguish the presence of SEC by each method. Similarly to the aforementioned studies, the results once more favored ICE use as a complementary tool to TEE for confirmation of thrombus presence where TEE was able to conclusively diagnose 1 case of LAA thrombus where ICE was able to identify 3 individual cases; in addition, a RA thrombus in one patient was only visible with ICE.
The result for SEC determination also indicates the superiority of ICE as it was able to determine a larger number of cases comparing to TEE. [7]
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Figure 7-Comparison of left atrial appendage (LAA) imaging for spontaneous echo contrast (SEC) with intracardiac echocardiography (ICE) and transesophageal echocardiography
(TEE). Top: LAA with both TEE (left) and ICE (right) in the same patient and at the same time. Moderate SEC is visualized at the distal LAA with ICE but not with TEE because of suboptimal
visualization of the distal LAA with TEE. Bottom: Right atrial appendage (RAA) with both TEE (left) and ICE (right) in the same individual and at the same time. ICE imaged the RAA from the body of the right atrium at a distance of 2 to 3 cm compared with the TEE transducer.
Anter E, Silverstein J, Tschabrunn CM, Shvilkin A, Haffajee CI, Zimetbaum PJ, Buxton AE, Josephson ME, Gelfand E, Manning WJ. Comparison of intracardiac echocardiography and transesophageal echocardiography for imaging of the right and left atrial appendages. Heart Rhythm. 2014 Nov;11(11):1890-7 [7]
10.6 Limitations of Intracardiac echocardiography-
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deter some patients from undergoing the procedure and although very rare, vascular complications may occur.
28 11. DISCUSSION
The present review revolved around the premise of using ICE as not only a valid method for the treatment of Afl, but rather as a far more effective one, specifically focusing on its capabilities to visualize the CTI and its anatomical properties, the assessment of the LAA, SCE or Thrombi occurring within it, both play a critical rule in the determination of procedural outcomes. With ICE becoming more prominent in recent years, it is of great importance to explore its beneficial value and technical capabilities or limitations, and to establish the indications for its routine use, not only as a complementary method but as the method of choice. The reviewed studies and literature were therefore chosen to elucidate these aspects by a comparative analysis of ICE to more prevalent techniques currently in use. The scarcity of information, currently available data and studies, further necessitate more investigation on this matter. [7, 11, 16, 17]
Throughout the review, ICE has been unequivocal, time after time, an invaluable, both as a complementary and definitive method for Afl management, depiction of CTI anatomical variations, identification of the pre-procedural presence of SCE’s and thrombi within the LAA, with an acute success rate concerning these parameters of close to 100%. Importantly it has been successful where other, more prevalent methods, such as TEE could not. [7, 12, 16,17]
Moreover, ICE allows for a zero-fluoroscopy environment during the procedure, this fact is beneficial to both patient and practitioner in avoiding radiation-associated complications such as carcinogenesis and tissue remodeling. ICE does not require anesthesia and allows the patient to stay awake, perform movements when required, and alert to potentially life-threatening processes he is experiencing during the procedure. Additionally when technical constraints arise with the use of TEE, mainly inability to swallow a probe, undergo anesthesia prior, or various pathological processes that prevent esophageal access, the patient may be confidently referred to ICE.
Although the need to gain vascular access and the invasive nature of ICE pose a potential barrier to use the method, it is a rare occurrence and vascular complications are infrequent, this difficulty has also been diminished by the introduction of new catheters. [22, 30]
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programs, as with any introduction of a novel medical practice, bears additional cost consideration and is taken into consideration by institutions.
It is difficult to quantify the real “cost-effectiveness” of employing ICE more often, although the method, short-term is more expensive than some, in some cases, its use is necessary for
confirmatory purposes additionally to an initial method of choice, in others it provides a faster, more efficient way to facilitate an ablative intervention with greater success rates, and as previously mentioned eliminates radiation and anesthetic requirements, and the adverse events which may arise, the long-term use of it as the primary method of choice may prove to be more cost-effective rather than more expensive.[40]
30 12. CONCLUSIONS
ICE used for atrial flutter ablation is a highly effective method for the definitive treatment of Afl. The technique allows for a real-time, intraoperative assessment of the CTI and LAA anatomical properties, is able to identify the presence or occurrence of SEC’s or thrombi, and has an incredibly high success rate, with a low rate of complications. ICE succeeds where other more conventional methods fail or provide equivocal findings. ICE allows for avoidance of radiation, compared with fluoroscopic investigations, does not require anesthesia, and overall shortens the procedural duration and RFA time and exposure.
Practical recommendations- The current scarcity of studies on ICE employment for Afl ablation necessitates more studies to be conducted, a "Solomonian judgment" as to one method's
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