The role of transesophageal echocardiography in predicting technical problems and complications of transvenous lead extractions procedures

Abstract Background Transesophageal echocardiography (TEE) is a useful tool in preoperative evaluation of patients undergoing transvenous lead extraction (TLE). Hypothesis Echocardiographic phenomena may determine the difficulty and safety of the procedure. Methods Data from 936 transesophageal examinations (TEE) performed at a high volume center in patients awaiting TLE from 2015 to 2019 were assessed. Results TEE revealed a total of 1156 phenomena associated with the implanted leads in 697 (64.85%) patients, including: asymptomatic masses on endocardial leads (AMEL) (58.65%), vegetations (12,73%), fibrous tissue binding the lead to the vein or heart wall (33.76%), lead‐to‐lead binding sites (18.38%), excess lead loops (19.34%), intramural penetration of the lead tip (16.13%) and lead‐dependent tricuspid dysfunction (LDTD) (6.41%). Risk factors for technical difficulties during TLE in multivariate analysis were: fibrous tissue binding the lead to atrial wall (OR = 1.738; p < 0.05), to right ventricular wall (OR = 2.167; p < 0.001), lead‐to‐lead binding sites (OR = 1.628; p < 0.01) and excess lead loops (OR = 1.488; p < 0.05). Lead‐to‐lead binding sites increased probability of major complications (OR = 3.034; p < 0.05). Presence of fibrous tissue binding the lead to the superior vena cava (OR = 0.296; p < 0.05), right atrial wall (OR = 323; p < 0.05) and right ventricular wall (OR = 0.297; p < 0.05) reduced the probability of complete procedural success, whereas fibrous tissue binding the lead to the tricuspid apparatus decreased the probability of clinical success (OR = 0.307; p < 0.05). Conclusions Careful preoperative TEE evaluation of the consequences of extended lead implant duration (enhanced fibrotic response) increases the probability of predicting the level of difficulty of TLE procedures, their efficacy and risk of major complications.


| INTRODUCTION
Transvenous lead extraction (TLE) is considered first-line strategy for the management of complications associated with cardiac implantable electronic devices (CIED). 1,2 Recently, due to the rising incidence of infectious and non-infectious CIED-related complications, the number of TLEs has also been increasing. 3 According to numerous reports, the frequency of major complications of TLE ranges from 0.9% to 4.0%, and most often there is damage to the heart or venous vessels. [4][5][6][7] Assessment of risk factors for major complications and procedure complexity should have an impact on the selection of a suitable organizational model of the procedure and center preferment . [4][5][6][7] The available TLE risk stratification scales most often take into account the impact of various factors on the technical complexity of the procedure 4-7 or periprocedural mortality. [4][5][6][7] They are based on demographic and clinical data (patient age, gender, presence of co-morbidities), type of CIED system (ICD lead, number of leads) and history of pacing (age at first implantation, number of leads designed for extraction). [4][5][6][7] This is the first study to assess the usefulness of new factors that may significantly affect the level of difficulty and procedure complexity as well as efficacy and complications of TLE. These factors were identified during an echocardiographic examination of patients selected for TLE due to CIED-related complications. Echocardiography, especially transesophageal echocardiography plays a key role in the evaluation of rhythm controlling devices (PM/ICD/CRT) and remains a valuable tool for precise imaging, which is recommended by experts. [8][9][10][11][12][13][14][15] Although a number of studies focused on the value of preoperative TEE findings (size of vegetations, presence of asymptomatic masses on the leads), the only echocardiographic parameter discussed when estimating the procedure-related risk was left ventricular ejection fraction (LVEF), only few studies so far have suggested that TEE can be used apart from fluoroscopy or computerized tomography 7 to choose optimal TLE strategy, 16,17 nevertheless the effect of echocardiographic findings on procedure safety and efficacy has not been assessed.

| Study group
We carried out a prospective analysis of the data from 936 preoperative TEE examinations performed at a high volume center before transvenous lead extraction from June 2015 to October, 2019.

| The extent of preoperative TEE
TEE was performed using the Philips iE33 or the GE Vivid S 70 ultrasound machine equipped with X7-2t Live 3D or 6VT-D probes.
Images were obtained before the procedure, after general anesthesia and tracheal intubation, during preparation of the surgical field and dissection and stabilization of the leads in the device pocket. Leads were evaluated in the mid-esophageal, inferior esophageal and modified transgastric views to visualize the right ventricle and the tricuspid valve. In order to obtain complete visualization of the structures (and assessment of lead/heart interaction) non-standard imaging planes were sometimes required. After the procedure the results were entered into a computer database. We analyzed the number, location and course of the leads: in the superior vena cava (SVC), right atrium (RA), right ventricle (RV) (taking into account excess lead loops). We also assessed lead mobility, presence of sites at which the lead was bound to cardiac structures, lead-to-lead binding sites and additional masses attached to the leads. An important part of the imaging protocol was assessment of the effect of the lead on tricuspid function.
Additionally, we assessed left ventricular function (LVEF), pericardial function and possible presence of structural heart disease (atrial or ventricular septal defects).

| Definitions of echocardiographic phenomena
1. Asymptomatic masses on endocardial leads (AMEL) characterized by homogeneous echogenicity, smooth contour and varying degrees of organization. AMEL include components of connective tissue (accretions), clots, masses resembling vegetations (so-called vegetation-like masses). Vegetation-like masses may be the remnant vegetations after antibiotic treatment or (less probable) organized fibrotic thrombi. 18 2. Hyperechoic segmental thickening of the leads defined as connective tissue overgrowth (undergoing fibrosis, mineralization, crystallization and even ossification). 18 3. Bacterial vegetations: multishaped, mobile masses of inhomogeneous echogenicity attached to the leads or/and to the neighboring anatomic structures, most frequently tricuspid leaflets. They were found only if they were accompanied by signs of a general infection. Sometimes coexisting with AMEL (vegetation-like masses). 18 4. Accretion-immobile fibrous connective tissue sheath around the lead causing adherence to the endocardium and vessel walls and producing images similar to segmental lead thickening but moving along with the cardiac wall. 18 5. Excessive lead loops -result of too weak fixation of the lead during implantation or lead fracture with break of insulation in the subclavian region. 18 6. Cardiac wall perforation by the lead: visualization of the lead tip outside the heart contour, sometimes with fluid in the pericardial sac; placement of the lead tip close to the border of the pericardium is referred to as penetration. 18

| Transvenous lead extraction procedures
Procedures were performed in a hybrid operating room or in an operating room, using mechanical systems such as polypropylene Byrd dilator sheaths (Cook ® Medical, Leechburg, PA, USA), making use of the oblique cutting edge of the tip to dissect leads from fibrous sheaths that immobilized the intravascular and/or intracardiac segment of the lead. 11,19 Procedures were performed in patients under general anesthesia with full preparation of the surgical field for cardiac surgery.

| Approval of the bioethics committee
All patients gave their informed written consent to undergo TLE and use anonymous data from their medical records, approved by the Bioethics Committee at the Regional Chamber of Physicians in Lublin no. 288/2018/KB/VII.

| Statistical analysis
The Shapiro-Wilk test was used to test the normality of distribution   Table 2) Comparative analysis of the impact of several echocardiographic parameters on the course and efficacy of TLE was presented in supplementary file.    (Table 3).    Another echocardiographic finding that is, fibrous tissue binding the lead to the adjacent heart and vessel structures deserves discussion, as so far the problem has received scant attention in the research literature . 20 In this study, fibrous tissue binding sites were recognized on inspection of the lead location and mobility with respect to one another and cardiac structures, looking for such signs as immediate vicinity, thickening and lead/heart wall mobility during cardiac work (Figure 1).

| Factors influencing the occurrence of technical difficulties-results of logistic regression analysis
The There are numerous studies 4-7 which on the basis of demographic data (age, sex), clinical information (indications, accompanying diseases, heart sufficiency), information about PM/ICD/CRT devices (number and type of leads) and history of pacemaker therapy (age of leads and route of implantation) show that initial patient assessment may identify the individuals in whom TLE may be more difficult or associated with the occurrence of major complications. Only few studies using scoring systems provide a more precise prediction of the level of procedure difficulty or estimate the true risk. 6,7 A review of the literature shows that so far echocardiographic findings have not been analyzed with respect to prediction of technical difficulties associated with TLE and complications of the procedure. Only one paper demonstrated that low LVEF was a predictor of major complications, 6 another paper documented an eventful postoperative course in patients with right ventricular dysfunction. 4 The evidence from another study suggests that information from CT examination may be useful for estimating procedure difficulty. 8 Yet another study implies that accurate Doppler blood flow measurements in the SVC may identify patients with significant lead fibrosis requiring powered sheaths for successful removal. Although numerous papers have emphasized the role of the connective tissue (scar tissue binding the lead to the SVC and heart wall) in estimating procedure complexity and its complications, 3,6,7 to the best of our knowledge we are the first to use the information about the degree of connective tissue build-up to predict technical difficulties and risk of major complications associated with TLE.
When developing a risk calculator for prediction of complications (SAFeTy TLE) 7 we found out that lead-to-lead binding site was an extremely important prognostic factor, however other information (S, sum of lead dwell times; A, anemia, Fe, female; T, treatment [previous procedures], Y , young patients) appeared more significant in multivariate analysis. We are of the opinion that all forms of connective tissue response (scar tissue binding the lead to the vein and heart structures, lead-to-lead adhesion) are extremely significant factors that increase procedure complexity and its radiological efficacy, however they do not necessarily translate into major complications at an experienced high volume center. Nevertheless, TEE before TLE should become a tool that provides additional information about procedure-related risk. Specific findings from echocardiography could have an impact on the procedure in term of logistic or in term of procedural steps.

| LIMITATIONS
This is a single-center, observational, prospective study. TLE was performed using mechanical systems without laser energy. Comparison of diagnostic sensitivity of TEE and ICE was not the aim of the study.