LITHUANIAN UNIVERSITY OF HEALTH SCIENCES ACADEMY OF MEDICINE
FACULTY OF MEDICINE DEPARTMENT OF CARDIOLOGY
GINTARĖ IVANAUSKAITĖ
Comparison of fluoroscopy and intracardiac echocardiography as guidance methods for transseptal puncture
Final master thesis Biomedical sciences,
Medicine
Thesis advisor:
Assoc. prof. Tomas Kazakevičius
Kaunas
LIST OF CONTENT
SUMMARY ...2
CONFLICT OF INTEREST ...3
BIOETHICS COMMITTEE APPROVAL ...3
ABBREVIATIONS ...4
DEFINITIONS ...6
INTRODUCTION ...7
1. GOAL AND OBJECTIVES ...8
2. LITERATURE ANALYSIS ...9
3. METHODOLOGY ...16
4. RESULTS ...19
5. DISCUSSION ...25
CONCLUSIONS ...27
RECOMMENDATIONS ...28
REFERENCE LIST ...29
SUMMARY
Author: Gintarė Ivanauskaitė
Title: Comparison of fluoroscopy and ICE as guidance methods for transseptal puncture.
Goal: To compare ICE and fluoroscopy as guidance tools for transseptal puncture.
Objectives: 1. To review literature to determine the advantages and disadvantages of fluoroscopic and intracardiac echocardiographic guidance for transseptal puncture. 2. To determine and compare statistical significance of anterior and posterior distances obtained from intracardiac echocardiography during transeptal puncture when guided by fluoroscopy and intracardiac echocardiography. 3. To compare which method is more accurate at localising the desired puncture site by analysing literature and using the results of this research data.
Methods: A statistical analysis and comparison of measurements anterior and posterior to the puncture needle on the intraatrial septum when guided by ICE and fluoroscopy.
Participants: All patients undergoing cryoablation for paroxysmal atrial fibrillation during September 2018 - February 2020 at the Hospital of Lithuanian University of Health Sciences (LSMU) Kauno klinikos.
Results: Based on parametrical Student t test for dependant samples a significant difference (p=0,03) between the anterior and posterior distance when guided by ICE was determined. Moderate correlation (rs =-0,512 p=0,03) between the anterior and posterior distance when guided by ICE was observed.
There was no correlation (rs =-0,315 p=0,107) between anterior and posterior distances when guided by fluoroscopy. Although, comparing anterior and posterior distances when guided by both ICE and fluoroscopy no statistical significance was observed (parametrical student t test for dependant variables). There were weak correlations between the size of the left atrium and the ratio of the anterior and posterior measurements when guided by fluoroscopy (rs =0,286 p=0,141) and when guided by ICE (rs =0,357 p=0,053). The size of the right atrium and the ratio of the anterior and posterior measurements were weakly correlated when guided by fluoroscopy (rs =0,201 p=0,305) and when guided by ICE (rs =0,248 p=0,186).
Conclusions: Although, all researchers conclude that ICE is a better imaging modality when guiding TSP there was not enough evidence to conclude that the difference between the TSP location when guided by ICE and fluoroscopy was statistically significant. The research should be continued in order to reach a larger sample size.
CONFLICT OF INTEREST
The author declares that there are no conflicts of interest.
BIOETHICS COMMITTEE APPROVAL
The approval Nr. BEC-MF-374 for this research was issued by LUHS Bioethics Centre in 2019-04-02.
ABBREVIATIONS
3D – three dimensional;
ACT – activated clotting time;
AF – atrial fibrillation;
AP – anteroposterior;
ASD - atrial septal defect;
CS – coronary sinus;
CW - clock wise;
EAM – electroanatomical mapping;
EHRA - European Heart Rhythm Association;
EP – electrophysiologist;
FO – fossa ovale;
IAS – intraatrial septum;
ICD-10 - International Classification of Diseases, Tenth Revision ; ICE – intracardiac echocardiography;
LA – left atrium;
LAA – left atrial appendage;
LAO - left anterior oblique;
LIPV - left inferior pulmonary vein;
LPV - left pulmonary vein;
LSPV - left superior pulmonary vein;
LUHS - Lithuanian University of Health Sciences;
LVAD - left ventricle assist device;
LVH – left ventricle hypertrophy;
MOSQ TSP - Mosquito transseptal puncture;
PBMV – percutaneous balloon mitral valvuloplasty;
PFO - patent foramen ovale;
PVI – pulmonary vein isolation;
RA – right atrium;
RAO – right anterior oblique;
RIPV - right inferior pulmonary vein;
RPV - right pulmonary vein;
RSPV - right superior pulmonary vein;
SPSS - Statistical Package for Social Sciences STE - ST elevation;
SVC - superior vena cava;
TEE – trans-esophageal echocardiography;
TSP – transseptal puncture;
DEFINITIONS
Atrial fibrillation – irregular heartbeat originating in the pulmonary veins;
Cryoablation – a process that uses cold to destroy desired tissues;
Fluoroscopy – an imaging mode which records continuous X-Ray images;
ICE – an imaging modality which provides real-time visualisation of cardiac structures;
Pulmonary vein isolation – a procedure used to treat atrial fibrillation;
TSP (transseptal puncture) – a procedure during which the intraatrial septum is punctured;
INTRODUCTION
Transseptal puncture (TSP) is becoming more widely used as there are more percutaneous cardiac interventions done. As the numbers of newly diagnosed atrial fibrillations (AF) are set to increase electrophysiologists (EP) will have to perform more pulmonary vein isolation (PVI) procedures all of which require transseptal puncture [1]. Locating the true puncture site can be quite difficult and if done incorrectly can lead to a prolonged hospital stay and serious complications [2]. To this day fluoroscopy remains the most widely used guidance method for TSP but as better imaging methods emerge a question could be raised whether fluoroscopy is as precise as assumed.
There is a lot of research discussing advantages and disadvantages of both methods which will be thoroughly reviewed in the literature analysis part. There is data that suggests that ICE is a better imaging modality but no research comparing the two methods. The Hospital of Lithuanian University of Health Sciences (LSMU) Kauno klinikos is able to use both methods during PVI and it was decided to compare which one is more precise. There fore, this research aims to compare two different methods: fluoroscopy and ICE for TSP guidance.
1. GOAL AND OBJECTIVES
Goal:
To compare ICE and fluoroscopy as guidance tools for transseptal puncture.
Objectives:
1. To review literature to determine the advantages and disadvantages of fluoroscopic and intracardiac echocardiographic guidance for transseptal puncture.
2. To determine and compare statistical significance of anterior and posterior distances obtained from intracardiac echocardiography during transeptal puncture when guided by fluoroscopy and intracardiac echocardiography.
3. To compare which method is more accurate at localising the desired puncture site by analysing literature and using the results of this research data.
2. LITERATURE ANALYSIS 2.1.Transseptal puncture
Transseptal puncture (TSP) is a necessary step in electrophysiological (EP) procedures when it is necessary to reach the left atrium. It is used for ablations of arrhythmias originating in the left side of the heart, left atrial appendage closure, mitral valve procedures and other catheter based structural heart procedures [3]. The first TSP was described in 1959 by Ross, Braunwald and Morrow [4] and became increasingly popular once pulmonary vein isolation (PVI) and percutaneous balloon mitral valvuloplasty (PBMV) were introduced [5]. Since then a lot of different techniques were developed to make it more safe and efficient. Routinely, TSP is done under fluoroscopy to locate fossa ovalis, the preferred anatomical position for puncture [6]. Due to the short comings of conventional fluoroscopy (high levels of exposure to ionising radiation to both patient and clinician, no direct visualisation of the septum) researchers are searching for novel methods, whether it is zero-fluoroscopy transseptal puncture using electroanatomical mapping (EAM) and intracardiac echocardiography (ICE) [7], non- fluoroscopic three-dimensional (3D) mapping system [8] or non-fluoroscopic MediGuideTM assisted tracking system without the use of ICE [9]. However, ultrasound guided (transesophageal echocardiography (TEE), ICE) imaging methods, providing direct visualisation of the intra-atrial septum and surrounding tissues are becoming increasingly popular [5]. Onward, only two methods of transseptal puncture guided by intracardiac echocardiography and conventional fluoroscopy will be discussed as the aim of this thesis is to analyse and compare these methods and determine which is more accurate at localising the desired puncture site. It is impossible to identify the correct puncture site within the intraatrial septum (IAS) without clear understanding of the atrial anatomy and structures lying close to it. Therefore, analysis of the anatomy will be presented.
2.2.Anatomy of the intraatrial septum
It is very important to understand the anatomy of the true IAS because the TSP site should be within the borders of fossa ovale (FO). Anatomically, a septum in the heart is defined to be a structure separating two chambers and if removed, access to the other chamber would be possible without exiting the heart itself. Therefore, the true IAS rim is the flap valve of fossa ovale. The flap valve is attached to the muscular rim of the IAS which is believed to be formed from the septum secundum and is nothing more than an invagination of the atrial walls with extra-cardiac fat insertions [10].
According to measurements done by ICE and fluoroscopy the average vertical diameter of FO is 18,5+-6,9mm and the average horizontal diameter is 10,0+-2,4mm [11].
The size and location of the FO can vary from person to person, also anatomical changes of the thorax or cardiovascular system (kyphoscoliosis, LVH) can have an effect on it [12].
As FO is a very small structure, which typically has to be localised using fluoroscopy without direct visualisation and on a 2D representation, even an experienced operator can cause complications of the procedure. The mechanism leading to iatrogenic TSP complications is accidental puncture of structures that lie close to the FO. A puncture through the muscular IAS could cause hemoperricardium especially because the patients undergoing TSP are in a hypo-coagulable state. The anterior rim of the FO is in close proximity of the aortic mound and a subsequent puncture in this region could lead to aortic perforation [13].
Previously, the aim of TSP was to cross the septum and fluoroscopy provided enough information to do so but with more percutaneous procedures being done the discussion of site-specific TSP began. For example, the site differs when using central or lateral jets during mitral valve interventions, but in general should be posterior and slightly superior, for left atrial appendage (LAA) closure a posterior-anterior approach should be considered, for PVI a more anterior site ensures the best reach for all pulmonary veins (PV) especially the right inferior pulmonary vein (RIPV). When crossing the septum for LVAD the fossa ovale should be crossed in the middle for the best result (Figure 1). Fluoroscopy does not provide direct visualisation of the IAS and FO that is why echocardiographic imaging techniques (TEE, ICE) have become invaluable for site-specific TSP [14].
Figure 1. Site specific TSP. Red - MitraClip, yellow - transseptal PFO closure, blue - percutaneous LVAD placement, green - LAA closure, orange - PVI
(Alkhouli M.)
2.3.Transseptal puncture procedure
Typically, TSP is done under fluoroscopic guidance. A standard right-sided femoral vein puncture is required due to a more linear approach towards the right atrium (RA). Fluoroscopy or ultrasound can be used to guide a safe venous puncture. Alternatively, it can be done without any imaging techniques by palpating the femoral pulse and puncturing it medially and 4cm below the inguinal ligament [15]. A catheter can be placed in the coronary sinus (CS) for intracardiac rotation evaluation. If needed, a pigtail catheter can be introduced and its tip placed in the posterior non- coronary sinus of the aortic valve to define the aorta [16]. The best fluoroscopic angles for the procedure are right anterior oblique (RAO) and left anterior oblique (LAO) but an anterio-posterior (AP) can also be used. Once the catheters used as landmarks are inserted the preparation for TSP can begin. Firstly, the transseptal (TS) needle, sheath and dilator should be flushed with heparin to avoid any air bubbles in the equipment. A guide-wire can be advanced to the superior vena cava (SVC) and the sheath with a dilator can be advanced over the guide-wire. When the sheath is in the SVC the wire can be removed and the TP needle can be advanced until around 3-4cm to the tip of the sheath to avoid any damage [16]. Once the sheath with the dilator and the TP needle are in the SVC positioned between 4-6 o’clock the operator starts to gently pullback the apparatus and two jumps can be seen on the fluoroscope screen. The first jump represents the apparatus falling into the RA and the second one in the fossa ovale. To ensure the correct position pressure monitoring or injecting contrast material into the septumcan be used. The tip of the needle can be advanced to the left atrium (LA) [15,16,17]. After confirming that the tip of the needle is in the LA, the dilator can be advanced. A guide-wire can be advanced into the left superior pulmonary vein to confirm the correct position.
Recently, a modified TSP technique was proposed called Mosquito technique (MOSQ TSP), where a thin inner stylet was inserted into the Brockenbrough TSP needle and used to puncture the already stretched septum. Research comparing the conventional and MOSQ TSP found that the mosquito technique is effective, safe and less time consuming meaning less exposure to radiation [18].
Procedures in the left atrium or ventricle can be carried out after successful puncture of the septum.
2.4.Intracardiac echocardiography guided transseptal puncture
The first TSP carried out with the use of two-dimensional echocardiography was described in 1984 when doctors were looking for new ways to avoid the complication of intrapericardial aortic puncture [19].
Currently, two different ICE systems are available for use: phased array and a rotational probe. The phased array probe provides 90° sector images with changeable depth control and is located on an 8 Fr steerable catheter, which provides better manoeuvrability and is the preferred probe for use.
The second transducer comes on a non-steerable catheter but provides a 360° rotational view in the radial plane [20].
Usually, the phased array probe is used for TSP. Following a right-sided femoral vein puncture and TSP sheath and dilator insertion a standard femoral vein puncture is required for the insertion of the ICE catheter into the heart and can be easily achieved without fluoroscopic guidance.
The general idea of placing the catheter in the heart is to avoid advancing it when echogenic space is seen and using retroflexion and anteroflexion for acute and obtuse angles. The image seen on the screen of the ultrasound will be perpendicular to the to the long axis of the probe [21].
Once the probe is in the RA the ‘home view’ (long-axis view of the right ventricle and tricuspid valve) is identified. With a 45° clock-wise rotation a long axis view of the aortic root is seen.
At 90° (clock-wise) CW rotation the mitral annulus and LAA come into view, further CW rotation brings LPV into view and is useful in determining their morphology i.e. if they share a common ostium. 180° rotation of the ICE catheter will provide information about the location of the esophagus and its relation to right pulmonary veins (RPV) and left pulmonary veins (LPV). Further CW rotation lets the operator visualise RPV, their morphology and relation to the IAS. The ostium of the LPVs should be used as a point towards which the transseptal sheath should be directed. Once the TSP is performed ICE can be used to ensure that the sheath is in the LA [22].
ICE is an invaluable tool in identifying procedural complications like pericardial effusion/
tamponade, intracardiac thrombus or sheath-associated thrombi. There is no need for an experienced sonographer during the procedure as cardiac electrophysiologists with previous echocardiography experience can quickly learn to navigate and recognise the images on ICE [23].
By using ICE the physician is able to directly identify the LA, IAS and the position of the needle on it. It also provides valuable information about the anatomy of the septum itself, whether it is thickened, sloppy, aneurysmatic, hypertrophied or if the FO is patent and/or atrial septal defect (ASD)
that has been previously surgically repaired or if there is a thrombus in LAA. Based on this information the operator can choose a different approach or decide to terminate the procedure [24].
According to the results of the EHRA survey only 16.7% of centres use ICE or TEE for TSP routinely, 58.3% in difficult cases and 25% do not use it at all [25].
All operators using ICE for TSP conclude that it is superior comparing with conventional fluoroscopy but many are not able to use it routinely because of the expenses.
The cost of a single phased-array ICE catheter can average to $2100. Using ICE for every TSP can be cost-intensive but it could save expenses due to shorter procedure times, avoiding general anaesthesia and complications, less exposure to radiation and shorter hospital stays. Insurance agencies tend to not cover the costs of ICE use in Europe, but re-sterilization and re-use of catheters, which is permitted in Germany and eastern Europe lowers the expenses significantly [26].
Below, advantages and disadvantages of both imaging methods are summarised.
Table 1. Advantages and disadvantages of ICE and fluoroscopy
Imaging method Advantages Disadvantages
ICE Direct visualisation of IAS and surrounding structures
Early detection of periprocedural complications
Visualisation of LAA or catheter associated thrombus
No need for general anaesthesia or second operator as in TEE Shorter procedure time and less exposure to radiation
Expensive and usually not covered by insurance
Need for a second femoral vein puncture
Fluoroscopy Cost-effective
Possibility to overlap with CT or CARTO images
No direct visualisation of IAS and surrounding structures Exposure to radiation
2.5. Complications of TSP
It is vital to know the most common complications of TSP to understand the decision of some operators to use ICE. Periprocedural complications following TSP are rare but can be life threatening.
The most common complication is cardiac tamponade with a reported incidence rate of about 1-1,9%
[27, 28, 29].
A research on safety of fluoroscopy guided TSP analysed 4690 patients for whom TSP was done between 2000 - 2015 in Karolinska University hospital. It concluded that the number of cardiac tamponades which needed pericardial drainage after TSP was 34 out of which only 28 (0,59%) could be related to TSP. Also, the rate of tamponades was higher in the AF group [17].
The mechanism leading towards this complication is an inadvertent puncture of structures lying posterior to the FO. If the puncture is done more anteriorly than usually, the aortic root might be punctured.
Wasmer et al. found that the incidence of aortic puncture out of 4305 TSPs done on 2936 patients was 0,05% [30].
TSP could also be the cause of acute unstable iatrogenic ASD when larger sheath devices are used in a patient with severely reduced ejection fraction and could potentially lead to hypotension, cardiogenic shock and death [31, 32].
According to McGinty at al. the incidence of immediate post-procedural iASD is as high as 87% with 15% of them persisting after 18months of follow-up but not causing cyanosis, embolism or RHF [33].
Transient ST segment elevations (STE) are also a possible complication of left heart catheterisation with an incidence rate of 0,38%. STE are followed by a drop in blood pressure and heart rate and complaints of pain and dizziness and are usually resolved with a dopamine or saline drip [34].
A thrombus could form during the procedure but proper anticoagulation of the patient minimises the risk significantly. The combined incidence of a thromboembolic event following a transseptal ablation procedure in patients without cardiac implantable electronic devices and using oral anticoagulants was 1,5 per 100 person-years over a mean follow-up of 2,1 years [35].
Complications can also arise due to the inexperience of the operator. A study on the learning process of TSP demonstrated that it is a learning curve and around 29 TSPs are needed to pass the steepest slope of it [36]. Matoshvili et al. proposed that the rate of complications is directly
proportional to the experience of the operator and found that after 101 TSPs the incidence of tamponades decreased to 0,4% from 1,3% during the first 50 - 100 TSPs [17].
Below, the incidence rates of aforementioned complications are summarised.
Table 2. Complications of TSP and their incidence rate.
Complication Incidence rate Authors
Cardiac tamponade 0,59 %
1,3%
1,9%
Matoshvili et al. 2017 Cappato et al. 2010
Baman et al. 2011
Aortic root puncture 0,05 % Wasmer et al. 2016
Postprocedural ASD Immediate 87%
Persistent after 18months follow-up 15%
McGinty et al. 2011 McGinty et al. 2011
ST elevation 0,38 % Tang et al. 2014
Thromboembolic event 1,5 per 100 person-years Madhavan et al. 2016
3. METHODOLOGY
The aim of the research was to compare ICE and fluoroscopy guided TSP locations and to determine which method was more precise. In order to compare them the researcher has decided to measure 4 distances on the ICE machine: anterior and posterior to the puncture needle when guided by ICE and fluoroscopy. The anterior distance was bounded by the puncture needle inferiorly and the aortic root superiorly, where as the posterior distance was bounded by the puncture needle superiorly and the muscular part of the IAS inferiorly (Figure 2).
34 patients undergoing pulmonary vein cryoablation for atrial fibrillation treatment during the time period of September 2018 to February 2020 were included into the study. All the ablations were performed in the Hospital of Lithuanian University of Health Sciences (LSMU) Kauno klinikos. There were multiple operators performing the procedure and a single researcher recording all the data to eliminate research bias. The only exclusion criteria for patients were patent foramen ovale (PFO) or atrial septal defect (ASD) previously confirmed on TTE. The patients were informed that at least 4 weeks of systemic anticoagulation at a therapeutic level was required before the procedure. Prior to the ablation procedure TTE and CT with 3D reconstruction of LA and PVs were done. During the procedure mild sedation was used.
A standard right femoral vein puncture was done and an 8 French transseptal sheath and dilator were advanced until the SVC over a guide-wire. After the guide-wire was removed, a Brockenbrough needle was advanced. The tip of the needle was retracted into the dilator. The ICE catheter was introduced through a standard left-side femoral vein puncture and positioned in the RA and the ‘home’ view was identified. The dilator and needle were then positioned to 4-5 o’clock direction in relation to the body surface and considering that it is towards the IAS. This was done under fluoroscopic control in the AP position. Then the puncture device was retracted until a second
‘jump’ which indicates the FO location could be seen on fluoroscopy. The images of the dilator in this position were recorded on fluoroscopy and ICE. Then ICE was used to identify the desired position of the TSP and if needed the dilator was moved. The images were then stored again. Following the confirmation of the puncture site, the needle was advanced across the IAS and immediately after 100IU/kg of Heparin was administered aiming for ACT >350s. ACT values were checked in 20 min intervals. After confirming the position of the needle in the LA the transseptal apparatus was stabilised, the needle removed and a guide-wire advanced towards LSPV. Subsequently, isolation and cryoablation of all 4 PVs were performed. To prevent an atrio-esophageal fistula from forming
esophageal temperature was monitored through-out the procedure. During cryoablation of the RSPV and RIPV the vagus nerve was stimulated with the CS catheter to prevent damage to it.
Once, the procedure was finished images stored on the fluoroscopy and ICE machines were examined, measurements were taken and noted. The length of the IAS, the position of the needle on the septum after standard fluoroscopic TSP technique and the position confirmed by ICE were measured during atrial diastole on the ICE machine. The fluoroscopy device used in the Hospital of Lithuanian University of Health Sciences (LSMU) Kauno klinikos does not have an inbuilt standardised measurement system. It is possible to measure distances on the fluoroscopic images using additional measurement aids but the researcher decided to not use this method as the accuracy would be doubtful. Therefore all the anterior and posterior distances where measured on the ICE machine as it uses a standardised measuring system.
Distances anterior and posterior to the needle were measured. The anterior distance was bounded by the aortic root and the puncture needle and the posterior distance by the puncture needle and the muscular part of the IAS (Figure 2).
Figure 2. Anterior (A or dist. 1) and posterior (B or dist. 2) distances on the IAS guided by fluoroscopy measured on the ICE machine during atrial diastole.
The sizes of the right and left atrium used in the research were obtained from previously performed echocardiography found in the patients case history. The number of pulmonary veins and their diameter were obtained from a 3D cardiac computer tomography reconstruction performed pre- operatively in the out-patient department. The 3D cardiac CT reconstruction images were accessed
through the MedDream system. The IAS length was measured on the ICE machine during atrial diastole.
Statistical analysis was calculated using IBM SPSS Statistics. The sample size of the study was first calculated using information available from the database of the Lithuanian Hygiene Institute.
The total amount of newly registered cardiac arrhythmias which fall under the ICD-10 code group I44- I49 during the year 2018 were 134829. The sample size needed for a population of 134829 at a confidence level of 95% should be 383.
According to the data published in the EHRA White Book 2017 there were 3 centres offering AF ablations in 2016 and there were 113 ablations done in all 3 in 2016. At a 95% confidence level with a population of 113 the sample size should be 83. But the study was carried out in only one of the three electrophysiology centres therefore a decision was made to include every patient which came to the Hospital of Lithuanian University of Health Sciences (LSMU) Kauno klinikos for pulmonary vein cryoablation during the time period of 2018 September and 2020 February and exclude patients for whom TSP was not performed because of a PFO. Out of 35 patients only 1 had a PFO and was excluded, therefore the sample size was determined to be 34.
4. RESULTS
Descriptive statistics
There were 24 males and 10 females in the study. Males and females represented 70,6% and 29,4% of the population, respectively. According to the data available from the Hygiene Institute in Lithuania 43% of all the patients diagnosed with a disease which falls under the ICD-10 code group I44-I49 43% were male and 57% female. This difference might appear because the ICD-10 code group involves all cardiac arrhythmias but the study focuses on only one. Mean age between both age groups was found to be 55,75 ± 11,05 years and 54,60 ± 10,00 for males and 58,66 ± 13,58 for females. On average the left atrium size was 42,58 ± 5,57 mm in males and 41,30 ± 2,49 mm in females. The right atrium size was 42,04 ± 4,53 mm and 39,10 ± 4,67 mm in males and females respectively. There were 27 patients that had 4 pulmonary veins, 5 males and 1 female that had 5 and 1 male that had 6. The average diameter of the right superior pulmonary vein was 2,00 ± 0,64 cm in males and 1,71 ± 0,43 cm in females, where as the right inferior vein was 2,66 ± 0,41 cm and 1,70 ± 0,21 cm. The left superior and inferior veins were 1,83 ± 0,38 cm and 1,69 ± 0,38 cm in males and 1,71 ± 0,23 cm and 1,58 ± 0,20 cm in females. The additional right pulmonary vein was 1,14± 0,29 cm on average in males. The IAS was found to be 21,96± 6,26 mm in females and 19,99± 5,65 mm in males on average.
Table 3. IAS length results.
The mean distances anterior and posterior to the puncture needle guided by fluoroscopy were 11,95 ± 4,96 mm and 12,94 ± 6,26 mm respectively and 11,19± 2,79 mm anteriorly and 12,41 ± 3,50 mm posteriorly when guided by ICE. There were 3 cases when the anterior distance was missing and 2 cases when the posterior distance was missing when guided by fluoroscopy which means that the needle was positioned either on the aortic root or on the muscular rim of the IAS.
Statistical data comparing the two methods
Measurements of anterior and posterior distances guided by fluoroscopy
It was determined that the anterior and posterior distances follow a normal distribution (Kolmogorov-Smirnov test). The table bellow (Table 4) indicates the mean and standard deviation of the anterior and posterior distances when guided by fluoroscopy. The mean distances anterior and
IAS length, mm N Mean Std. deviation Std. error of mean
Men 24 19,99 5,65 1,15
Women 10 21,96 6,26 1,97
posterior to the puncture needle guided by fluoroscopy were 11,95 ± 4,96 mm and 12,94 ± 6,26 mm. It should be noted that there were 31 cases. 3 cases were missing because the needle was either on the aortic root or on the muscular part of the IAS. The distances were not noted as 0 mm to avoid any outliers.
Table 4. Means of anterior and posterior distances when guided by fluoroscopy.
A paired samples t-test was conducted to compare the anterior and posterior distance when guided by fluoroscopy. Table 5 indicates the correlation between the anterior and posterior distances when guided by fluoroscopy. A non-parametric Spearman correlation was run to determine a relationship between anterior and posterior measurements. There was a non significant negative weak correlation rs = -0,305 p = 0,107. In this case, a negative correlation should be observed because as the anterior measurement increases the posterior decreases.
Table 5. Paired sample correlations of distances when guided by fluoroscopy.
The figures bellow (Figure 3,4,5) were taken from one patient. Figure 3 shows fluoroscopic images of the TSP location as guided by fluoroscopy and ICE. The second figure also refers to the puncture site. This clearly represents the difference between fluoroscopic and ICE guided TSP locations.
Mean N Std. deviation Std. error of mean
Anterior distance, mm
11,95 31 4,96 0,92
Posterior distance, mm
12,94 32 6,26 1,14
Pair 1 N Correlations Significance
Anterior distance, mm
& posterior distance, mm
31 -0,305 0,107
Figure 3. Patient number 4. Fluoroscopy images after needle placement guided by fluoroscopy and ICE. A - Brockenbrough needle, B - CS catheter, C - ICE.
The figures bellow are ICE images showing the TSP needle on the IAS after fluoroscopic (Figure 4) and ICE (Figure 5). Distance 1 is the distance anterior to the needle and 2 refers to the distance posterior to the needle. It can be seen that when guided by ICE (Figure 5) the needle is more in the middle part of the IAS than when guided by fluoroscopy (Figure 4).
Figure 4. Patient number 4. Needle placement on the IAS after fluoroscopic guidance measured on ICE machine. Distance 1 - anterior measurement, distance 2 - posterior
measurement, distance 3 - IAS length.
Figure 5. Patient number 4. Needle placement on the IAS after ICE guidance measured on ICE machine. Distance 1 - anterior measurement, distance 2 - posterior measurement,
distance 3 - IAS length
Measurements of anterior and posterior distances guided by ICE
It was determined that the anterior and posterior distances guided by ICE follow a normal distribution (Kolmogorov-Smirnov test). The mean distances anterior and posterior to the puncture needle were 11,19 ± 2,79 mm and 12,41 ± 3,50 mm when guided by ICE.
Table 6. Means of anterior and posterior distances when guided by ICE.
A paired samples t-test was conducted to compare the anterior and posterior measurements.
The table below indicates correlation between the anterior (mean=11,19 ± 2,79 mm) and posterior (mean=12,41 ± 3,50 mm) distance when guided by ICE. There was a significant difference (p=0,03) between the anterior and posterior measurement means when the puncture location was guided by ICE.
A non-parametric Spearman correlation was run to determine a relationship between anterior and posterior measurements. There was a significant negative moderate correlation r = -0,512 p = 0,03.
Mean N Std. deviation Std. error of mean
Anterior distance, mm
11,19 34 2,79 0,49
Posterior distance, mm
12,41 34 3,50 0,61
Figure 6. Means of anterior and posterior distances when guided by ICE.
Table 7. Paired sample correlations of distances when guided by ICE.
This suggest that TSP guided by ICE was more precise as the measurements were more similar to one another as the needle was more in the centre. The measurements anterior and posterior to the needle when guided by fluoroscopy varied greatly which lead to decide that the method was inferior to ICE. Dependant sample t-test was used to compare the mean differences between posterior and anterior measurements when guided by ICE. The image below reflects the significant difference (p=0,03) between anterior and posterior measurements when guided by ICE (Figure 6).
Pair 1 N Correlations Significance
Anterior distance, mm
& posterior distance, mm
34 -0,512 0,03
Distance V[95% PI], mm
0 2,571 5,143 7,714 10,286 12,857 15,429 18
Anterior distance Posterior distance 12,41
11,19
11,19[10,18-12,20] 12,41[11,15-13,67]
p=0,03
Comparison of anterior and posterior measurements guided by ICE and fluoroscopy Kolmogorov-Smirnov test was used to identify if all 4 variables (anterior and posterior distances when guided by ICE and anterior and posterior distances when guided fluoroscopy) follow a normal distribution. A paired samples t-test was conducted to compare the 4 variables.
Table 8. Paired samples test for measurements when guided by ICE and fluoroscopy.
There were no significant difference in the scores for the anterior measurements when guided by ICE (mean=11,19 ± 2,79 mm) and fluoroscopy (mean=11,95 ± 4,96 mm) t(30)=-1,035 p=0,309.
No significant difference was observed in the scores for the posterior measurements when guided by ICE (mean=12,41 ± 3,50 mm) and fluoroscopy (mean=12,94 ± 6,26 mmm) t(31)=-1,498 p=0,634.
There was not enough evidence to suggest that ICE is more precise than fluoroscopy but it could be argued that as the sample size increases the differences between the measurements will become statistically significant.
Additionally, analysis on the sizes of the left and right atrium and the relation between the guidance method was performed. There were weak correlations between the atrial sizes and the ratio of anterior and posterior distances when guided by fluoroscopy and ICE. The left atrial size and the distance ratio when guided by ICE were slightly more correlated (rs =0,357 p=0,053) than when guided by fluoroscopy (rs =0,286 p=0,141). The same tendency was observed when calculating correlations between the right atrium size and ICE (rs =0,248 p=0,186) and fluoroscopy (rs =0,201 p=0,305). This result could indicate that as the atrial sizes increase fluoroscopic guidance becomes less accurate than ICE. In order to determine whether the sizes of both atria affect the preferred guidance method a more in depth research should be carried out. An assumption could be made that if the sample size were to increase the correlations could become significant.
t df Sig. (2-tailed)
Pair 1/ anterior distance in ICE, mm - anterior distance in fluoroscopy,
mm
-1,035 30 0,309
Pair 2/ posterior distance in ICE, mm -
posterior distance in fluoroscopy, mm
-0,481 31 0,634
5. DISCUSSION
This researched aimed to comparing two different imaging methods for TSP. The comparison of these methods using mathematical evidence and statistical analysis are carried out to determine statistical significance but patient-oriented outcomes are as important [37]. This research demonstrated that using ICE as a guiding tool for TSP is a more precise method when compared with fluoroscopy.
According to the survey from EHRA only 16.7% of centres use ICE or TEE for TSP routinely and no data comparing ICE and fluoroscopy where found so it was not possible to compare it with the results of this research. [25] Even though, this result is very important for patients because it proved that the safer option is also a more precise one. In the literature analysis it was discussed that a lot of authors state that ICE is an expensive guidance tool for TSPs but it is superior to all others. [26] This research did not focus on cost-effectiveness of both methods but it proved that ICE is more precise at locating the puncture site, which also provides more safety for the patient.
Previous studies found that the rate of cardiac tamponades following TSP varies from 0,59%
to 1,9%. Out of 34 patients that were involved in this research there were 3 cases when after fluoroscopic guidance the TSP needle was either on the aortic root or on the muscular rim of the IAS.
Complications that arise from in-advert puncture of structures surrounding the IAS were avoided only because the position of the needle was corrected with ICE.
Previous studies discussing the benefits of ICE in guiding TSP have demonstrated that the procedure times were shorter and there is no radiation involved. Although this research did not investigate procedure times it could be discussed that it saves time because it can provide more information than fluoroscopy. ICE allows early periprocedural complication detection which would require longer time if fluoroscopy would be used instead.
The research also tried to investigate the possible relation between increasing left and right atrial sizes and the precision of each method. Although, statistical significance was not determined it could be clinically important as increasing atrial sizes could affect the size of IAS.
As mentioned in the literature analysis part fluoroscopy uses ionising radiation to generate images, therefore using ICE is not only faster but also safer for the patient and staff. [7]
The concept of external validity should be applied to medical research. The sample size was randomised because all patients that required cryoablation for AF were included but patients that had the same procedure done in different hospitals were not. The study can be easily replicated in other
electrophysiological centres which can use fluoroscopy and ICE which ensures external validity of this research.
The research should be considered internally valid as there was only one researcher taking the measurements, the distances were measured using the ICE machine which has a validated measuring system and a decision was made by the researcher to not include measurements taken on fluoroscopic images due to their possible inaccuracy.
The study limitations that were discussed in this research were that the data collected was obtained only in one of the electrophysiological centres. It would be beneficial if the study were to continue across all centres doing this procedure in Lithuania to reach a larger sample size. The other limitation was the time period in which the research was carried out. If it were continued for a longer time the sample size would have been larger. Also, the number of cryoablations for AF is regulated by the governmental authorities. This research did not measure distances to structures lying in front of the transseptal needle when on the intraatrial septum, which could only be done on ICE and could further prove the superiority of this guidance method.
All in all, using ICE for TSP proved to be more precise and safe by this research. Other authors have concluded that this method is superior but too expensive and most insurances do not cover the expenses but a price should not be placed on patient safety.
CONCLUSIONS
1. According to the literature analysis ICE is superior to fluoroscopy as it provides direct visualisation of the intraatrial septum, is more precise at locating the puncture site, the procedure is shorter and there is no radiation involved which makes it safer for the patient and the operator.
2. There was a significant difference (p=0,03) between the anterior and posterior distance based on parametrical Student t test for dependant samples when guided by ICE, also, the anterior and posterior distance when guided by ICE had moderate correlation (rs =-0,512 p=0,03).
3. The anterior and posterior distance when guided by fluoroscopy had no significant difference (p>0,05) or correlation (rs =-0,315 p=0,107).
4. The data from this research from 34 patients (data from 31 patients were used, as 3 outliers were removed for more accurate statistical evaluation) which where hospitalised for cryoablation during the period from September 2018 to February 2020 suggests that there was not enough evidence to conclude that the difference between ICE and fluoroscopy for guiding TSP location was statistically significant.
RECOMMENDATIONS
According to the literature analysis ICE is superior to fluoroscopy as a guidance method for TSP. After removing 3 patients for more accurate statistical evaluation for whom the needle was not on the septum after fluoroscopic guidance, the results of this research did not prove that ICE was more precise at guiding TSP than fluoroscopy. Regardless, when possible, ICE should be the preferred guidance method for procedures (cryoablation) requiring TSP especially during more challenging TSPs, as it helped to avoid any critical complications.
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