Residual echocardiographic and computed tomography findings after thoracoscopic occlusion of the left atrial appendage using the AtriClip PRO device

Residual echocardiographic and computed tomography findings after thoracoscopic occlusion of the... Abstract OBJECTIVES Thoracoscopic occlusion of the left atrial appendage (LAA) has become a routine part of thoracoscopic ablation for the treatment of atrial fibrillation (AF). Evaluation of residual findings of the occluded LAA by echocardiography has yet to be described. METHODS Patients with AF indicated for hybrid ablation (thoracoscopic procedure followed by catheter ablation) were enrolled in this study. LAA was occluded as a routine part of the thoracoscopic procedure. Follow-up transoesophageal echocardiography was performed at the end of the procedure, 2–5 days and 2–3 months after the procedure (before the endocardial stage). The residual pouches of the LAA were measured in the mitral valve view (30–110°) and in the perpendicular view. The depth of the residual pouch was measured from the ostial plane (connecting the Coumadin ridge and the circumflex artery) to the deepest part of the residuum. The volume of the residual pouch and the distance from the circumflex artery to the proximal and the distal ends of the AtriClip were measured using computed tomography. RESULTS Forty patients were enrolled in this study. The success rate for the occlusion of the LAA, assessed on transoesophageal echocardiography 2–5 days after surgery, was 97.5%. Regarding the residual findings, no reperfused LAAs were found, and only residual stumps remained. The depth of the stump was 12.9 ± 5.9 mm, the area was 2.2 ± 1.1 cm2, and the volume was 3.6 ± 1.9 ml (all data are shown as mean ± standard deviation). CONCLUSIONS The occlusion of the LAA using an AtriClip PRO device was a clinically safe procedure with high efficacy and was associated with the presence of a small residual pouch after occlusion. Clinical trial registration NCT02832206. Left atrial appendage, Occlusion, Stroke prevention, AtriClip PRO, Hybrid ablation INTRODUCTION Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia with a prevalence of 1–2% in the general population [1]. AF is associated with a 5-fold increased risk of a cardioembolic event [2]. The source of an embolic event is a thrombus, which can form in the left atrium (LA). According to data from autopsies and findings from transoesophageal echocardiography (TOE) in AF patients, approximately 90% of all left atrial thrombi arise in the left atrial appendage (LAA) [3]. In addition to oral anticoagulation (OAC), occlusion of the LAA has become the main non-pharmacological option for the prevention of cardioembolic events. Percutaneous catheter-based techniques for LAA occlusion (using a Watchman device) have been shown to be non-inferior to warfarin in prospective randomized trials [4]. Surgical closure of the LAA has been practised since 1948, primarily in patients with mitral valve disease [5]. It has been proposed that closure of the LAA decreases the risk for stroke in patients with AF, without the need for long-term anticoagulation. The rationale for this procedure is clear; however, several studies have documented frequent incomplete LAA closures, varying between 36% and 60% [6]. Moreover, some types of incomplete closures were associated with significantly higher risks of cardioembolic events than the risk predicted by the CHA2DS2VASc score [7]. Recently, occlusion of the LAA by clipping, using an external device (AtriClip® PRO, AtriCure, Inc., Cincinnati, OH, USA), was described [8]. The device can be used for epicardial clipping of the LAA during open-chest surgery or during thoracoscopic surgery (performed solely to clip the appendage or as a part of a minimally invasive thoracoscopic ablation for AF). Several reports assessing the procedural efficacy and stability of the device during follow-up have been published, with very promising results. However, the exact residual echocardiographic or computed tomographic (CT) findings of the LAA following LAA clipping, as reported for LAA excision and exclusion, are yet to be published. The goal of this study was to describe the procedural and post-procedural efficacy of thoracoscopic occlusion of the LAA (with AtriClips) and to describe residual echocardiographic and CT findings following LAA occlusion. Our other goal was to show the measured parameters in different time periods after occlusion to test whether there were any changes, with time, relative to the depth of the residual pouches after occlusion. METHODS Patients with AF indicated for hybrid ablation were studied. The inclusion and exclusion criteria, as well as project protocol, were previously published in detail elsewhere [9]. In brief, inclusion criteria were symptomatic, non-paroxysmal AF and the absence of significant structural, valvular or coronary heart disease. Exclusion criteria were AF secondary to a reversible condition or known severe pericardial adhesions. Other risk factors (age, comorbidities, LA diameter, AF duration, etc.) were assessed individually after a thorough discussion of the risks among the members of an informal AF team, comprising the cardiac surgeon, anaesthetist and electrophysiologist, and with the patient. AF types and definition of success were designed in accordance with actual recommendations [10], and the project was approved by the institutional ethics committee. All patients provided written informed consent. Surgical procedure A fully thoracoscopic, two-sided, off-pump, epicardial approach was used for the surgical ablation and LAA occlusion, as described in detail elsewhere [11]. The first part of the procedure, i.e. ablation of the posterior LA (‘box lesion’), was performed through a right thoracoscopy. During the procedure, a circumferential lesion was created anterior to the pulmonary veins with the goal of isolating all pulmonary veins and the posterior LA en bloc (the ‘box-lesion’ set). Lesions were created using a unipolar/bipolar linear radiofrequency COBRA Fusion™ 150 (Estech, an AtriCure® Company, San Ramon, CA, USA) catheter. If a patient remained in AF, a direct current cardioversion was performed. After ablation through the right chest had been performed, occlusion of the LAA, via a left thoracoscopy, was carried out using the AtriClip PRO device (AtriCure, Inc.). Single-lung ventilation was switched to the right side and the left hemithorax was entered with 3 working ports (third, fourth and sixth intercostal space). The pericardium was opened dorsally from the phrenic nerve. Next, the base of the LAA was measured, and the AtriClip PRO device was inserted via the inferior incision (which had to be enlarged to about 6 cm in length first) and carefully placed at the base of the LAA, with the goal of placing the device as close as possible to the bottom of the LAA, without covering the circumflex artery (CA). After closure of the clip, the position was checked using TOE: the goal was to create a residual pouch <10 mm in depth. When both the surgeon and the echocardiographer were satisfied with the position of the device, the AtriClip was released and the deploying system withdrawn from the thorax. Bleeding was staunched, and one drain was inserted prior to chest closure. Because the procedure was performed immediately after the completion of the thoracoscopic ablation, both procedures were done on heparin with a target activated clotting time (ACT) >300–350 s. For 2 h after surgery, patients received a continuous infusion of heparin with a target ACT of 180–200 s. Starting on the morning after surgery, patients were given low-molecular-weight heparin until effective OAC was achieved. OAC was continued for at least 3 months after surgery. Transoesophageal echocardiography Three TOE examinations were performed in all patients. The first examination was performed in the operating room before and during the thoracoscopic procedure. Before the procedure, the LAA was checked for thrombi formation, and LAA dimensions (ostium and landing zone) were measured. Moreover, attachment of the AtriClip (occlusion of the LAA) was carried out under TOE guidance. The second TOE was performed 2–5 days after surgery and the third TOE 2–3 months after surgery (prior-EP TOE). The goals were to check the position of the AtriClip PRO device, check for the presence of thrombi formation on the device and measure the residual pouch of the LAA. During all post-procedural TOE examinations, the morphology and size of the residual pouch of the LAA were assessed. The LAA pouch was visualized using different TOE probe angles. Measurements were made using the probe angle that offered the largest visualizable LAA pouch (typically between 30° and 90°). The ostium of the LAA was measured as the distance between the mid-CA and the top of the Coumadin ridge (i.e. the ridge between the left upper pulmonary vein and the LAA). The depth of the residual pouch was measured as the distance from the deepest part of the pouch to the plane of the ostium. The area of the pouch was measured as the area below the plane of the ostium. An example of the measurement of the LAA pouch is shown in Fig. 1. Figure 1: View largeDownload slide An example of the measurement of the residual stump after the occlusion of the appendage. First, a line was drawn connecting the ostium of the appendage, i.e. a line from the mid-circumflex artery to the top of the ridge between the left superior pulmonary vein and the appendage. Then, the depth of the stump was measured by dropping a perpendicular line from the aforementioned line to the deepest part of the appendage. Figure 1: View largeDownload slide An example of the measurement of the residual stump after the occlusion of the appendage. First, a line was drawn connecting the ostium of the appendage, i.e. a line from the mid-circumflex artery to the top of the ridge between the left superior pulmonary vein and the appendage. Then, the depth of the stump was measured by dropping a perpendicular line from the aforementioned line to the deepest part of the appendage. Cardiac computed tomography CT imaging was taken 2–5 months after the surgical procedure using a 256-detector row CT scanner (Brilliance iCT 256; Philips, Best, Netherlands). A triphasic injection of 60 ml of contrast media (Ultravist 370; Bayer Healthcare Pharmaceuticals, Montville, NJ, USA) was used. The first 50 ml of contrast agent was administered at a flow rate of 4.0 ml/s, followed by 20 ml of a 50/50 mixture of contrast and saline. Subsequently, a 30 ml saline flush was administered at a flow rate of 3.0 ml/s. Bolus tracking was used for synchronization of the contrast medium injection with scanning. The region of interest was positioned over the descending aorta. After the enhancement reached 140 HU, there was a 3-s post-threshold delay before the scan was commenced. Prospective electrocardiographic-triggered dose modulation (mode ‘step and shoot’) was the preferred method, using scanning at 70–80% of the RR interval. Image post-processing Data sets were transferred to an external workstation (Comprehensive Cardiac Analyses, Brilliance Workspace version 4.0; Philips Healthcare, Cleveland, OH, USA) for offline analysis. Axial slices, oblique reconstructions and maximum intensity projection images were used. For calculating the volume of the LAA pouch, 3-mm slices were used. Each slice of the LAA pouch was identified, and the borders were manually traced for volume assessment. In addition, the ostium of the left CA was identified and the distance to the end of the clip was measured, as suggested by Salzberg and Emmert [12, 13]. Statistical analysis Data from this study were tabulated using descriptive statistics. Continuous variables were presented as means and standard deviations (in a format mean ± SD), and categorical variables were presented as absolute and relative frequencies. The Shapiro–Wilk test was used to assess whether data were drawn from a normal distribution. To test the hypothesis that there were no changes in the investigated characteristics (depth and area) over time, a linear random-effects model was applied. Huber–White robust estimates of the standard errors were used to account for potential heteroscedasticity of errors. In cases with significant between-time differences, pairwise comparisons were done with Sidak’s correction for multiple testing. All tests were evaluated at a significance level of 0.05. All statistical analyses were done using Stata software, version 14.1 (Stata Corporation, College Station, TX, USA). RESULTS Patients and surgery Forty patients were enrolled in this prospective, observational study. The time frame for enrolment was from May 2015 to April 2017. Baseline clinical characteristics are presented in Table 1. Mean surgical time was 159.8 ± 27.6 min (including the previously performed left-sided thoracoscopic ablation), and the mean hospital stay was 7.7 ± 5.1 days. The device sizes used most often were 35 mm (implanted in 27 patients), followed by 40 mm (12 patients) and 45 mm (1 patient). The mean size of the ostium of the LAA before the implantation was 21.7 ± 3.7 mm. The devices were deployed in all patients. Table 1: Baseline patient characteristics Variables  Age (years), mean ± SD  62.6 ± 8.6  Male gender, n (%)  23 (57.5)  BMI (kg/m2), mean ± SD  30.3 ± 5.1  Hypertension, n (%)  21 (52.5)  Congestive heart failure (LVEF ≤40%), n (%)  10 (25)  Diabetes mellitus (%), n (%)  9 (22.5)  Stroke or TIA (%), n (%)  8 (20)  History of PCI (%), n (%)  1 (2.5)  CHA2DS2VASc score, mean ± SD  2.2 ± 1.47  LA diameter (mm) , mean ± SD  44.9 ± 8.8  LVEF (%), mean ± SD  52.3 ± 12.3  LVEDD (mm), mean ± SD  53.4 ± 4.8  Persistent AF, n (%)  14 (35)  LSPe AF  26 (65)  Variables  Age (years), mean ± SD  62.6 ± 8.6  Male gender, n (%)  23 (57.5)  BMI (kg/m2), mean ± SD  30.3 ± 5.1  Hypertension, n (%)  21 (52.5)  Congestive heart failure (LVEF ≤40%), n (%)  10 (25)  Diabetes mellitus (%), n (%)  9 (22.5)  Stroke or TIA (%), n (%)  8 (20)  History of PCI (%), n (%)  1 (2.5)  CHA2DS2VASc score, mean ± SD  2.2 ± 1.47  LA diameter (mm) , mean ± SD  44.9 ± 8.8  LVEF (%), mean ± SD  52.3 ± 12.3  LVEDD (mm), mean ± SD  53.4 ± 4.8  Persistent AF, n (%)  14 (35)  LSPe AF  26 (65)  AF: atrial fibrillation; BMI: body mass index; LA: left atrium; LVEDD: left ventricular end-diastolic diameter; LVEF: left ventricular ejection fraction; LSPe: long-standing persistent; PCI: percutaneous coronary intervention; SD: standard deviation; TIA: transient ischaemic attack. Table 1: Baseline patient characteristics Variables  Age (years), mean ± SD  62.6 ± 8.6  Male gender, n (%)  23 (57.5)  BMI (kg/m2), mean ± SD  30.3 ± 5.1  Hypertension, n (%)  21 (52.5)  Congestive heart failure (LVEF ≤40%), n (%)  10 (25)  Diabetes mellitus (%), n (%)  9 (22.5)  Stroke or TIA (%), n (%)  8 (20)  History of PCI (%), n (%)  1 (2.5)  CHA2DS2VASc score, mean ± SD  2.2 ± 1.47  LA diameter (mm) , mean ± SD  44.9 ± 8.8  LVEF (%), mean ± SD  52.3 ± 12.3  LVEDD (mm), mean ± SD  53.4 ± 4.8  Persistent AF, n (%)  14 (35)  LSPe AF  26 (65)  Variables  Age (years), mean ± SD  62.6 ± 8.6  Male gender, n (%)  23 (57.5)  BMI (kg/m2), mean ± SD  30.3 ± 5.1  Hypertension, n (%)  21 (52.5)  Congestive heart failure (LVEF ≤40%), n (%)  10 (25)  Diabetes mellitus (%), n (%)  9 (22.5)  Stroke or TIA (%), n (%)  8 (20)  History of PCI (%), n (%)  1 (2.5)  CHA2DS2VASc score, mean ± SD  2.2 ± 1.47  LA diameter (mm) , mean ± SD  44.9 ± 8.8  LVEF (%), mean ± SD  52.3 ± 12.3  LVEDD (mm), mean ± SD  53.4 ± 4.8  Persistent AF, n (%)  14 (35)  LSPe AF  26 (65)  AF: atrial fibrillation; BMI: body mass index; LA: left atrium; LVEDD: left ventricular end-diastolic diameter; LVEF: left ventricular ejection fraction; LSPe: long-standing persistent; PCI: percutaneous coronary intervention; SD: standard deviation; TIA: transient ischaemic attack. Regarding complications, 2 patients had to undergo surgical revision due to procedure-related bleeding. In both cases, the source of bleeding was the thoracic wall incision on the left side (i.e. the bleeding was assessed as procedure related). No bleeding complications stemming directly from the use of the AtriClip device (i.e. bleeding due to LA or LAA laceration) were noted. One of the 2 revision patients developed respiratory insufficiency, which required prolonged mechanical ventilation after the revision. Intraoperative transoesophageal echocardiography Careful checking of the devices at the end of the procedure revealed an LAA occlusion failure in 1 patient (Fig. 2). Despite what appeared to be proper device positioning, based on optical visualization using a camera, and adequate closure (as observed on TOE), the TOE at the end of the procedure revealed that the LAA was left almost completely open. The malposition of the Atriclip was later confirmed on cardiac CT (Fig. 2). In this patient, the depth of the residual pouch was 33 mm, and the area was 3.5 cm2. All other devices were implanted successfully with a mean depth of 11.45 ± 4.88 mm and an area of 1.70 ± 0.99 cm2. No leaks (‘narrow channel kind’ of failure) or thrombi were present at the end of surgery. Figure 2: View largeDownload slide An example of a patient with an unsuccessful occlusion of the left atrial appendage is shown. The AtriClip was placed very distally, and a large residual stump remained. (A and B) Transoesophagel echocardiography and (C and D) cardiac computed tomography. Figure 2: View largeDownload slide An example of a patient with an unsuccessful occlusion of the left atrial appendage is shown. The AtriClip was placed very distally, and a large residual stump remained. (A and B) Transoesophagel echocardiography and (C and D) cardiac computed tomography. Postoperative transoesophageal echocardiography (2–5 days after surgery) During the postoperative TOE, 1 patient was found to have a small shift of the device. The device shifted distally, and the depth of the pouch increased from 8 mm to 16 mm; similarly the area increased from 1.3 cm2 to 2.7 cm2. However, the distal trabeculated part of the appendage remained occluded, and only the residual smooth cul-de-sac portion of the proximal part of the appendage was shown on TOE, and it was of similar depth as that observed in other patients. Therefore, this shift was not assessed as a failure. The position of the device in all other patients remained stable, and no leaks or thrombi in the LAA pouch were detected. The depths and areas of residual stumps are presented in Table 2. The final efficacy was 97.5%, after including 1 patient with occlusion failure during surgery. Table 2: Data from all measurements Residual pouch size (TOE)  Intraoperative  2–5 days postoperative  Prior-EP (2–3 months after surgery)  Depth (mm), mean ± SD  11.45 ± 4.88  12.37 ± 6.90  12.94 ± 5.99  Area (cm2), mean ± SD  1.70 ± 0.99  2.17 ± 1.12  2.11 ± 1.05  LAA clip location (CT)   First distance to CX (mm), mean ± SD      20.00 ± 5.29   Second distance to CX (mm), mean ± SD      37.82 ± 5.83   Residual LAA volume (ml), mean ± SD      3.6 ± 1.9  Residual pouch size (TOE)  Intraoperative  2–5 days postoperative  Prior-EP (2–3 months after surgery)  Depth (mm), mean ± SD  11.45 ± 4.88  12.37 ± 6.90  12.94 ± 5.99  Area (cm2), mean ± SD  1.70 ± 0.99  2.17 ± 1.12  2.11 ± 1.05  LAA clip location (CT)   First distance to CX (mm), mean ± SD      20.00 ± 5.29   Second distance to CX (mm), mean ± SD      37.82 ± 5.83   Residual LAA volume (ml), mean ± SD      3.6 ± 1.9  Data from all measurements: 2–5 days after and 2–3 months after surgery. The depth and the residual area of the stump were measured using TOE as described in the Methods section and are shown in Fig. 1. The volume was measured using cardiac computed tomography. CT: computed tomography; CX: circumflex artery; LAA: left atrial appendage; SD: standard deviation; TOE: transoesophageal echocardiography. Table 2: Data from all measurements Residual pouch size (TOE)  Intraoperative  2–5 days postoperative  Prior-EP (2–3 months after surgery)  Depth (mm), mean ± SD  11.45 ± 4.88  12.37 ± 6.90  12.94 ± 5.99  Area (cm2), mean ± SD  1.70 ± 0.99  2.17 ± 1.12  2.11 ± 1.05  LAA clip location (CT)   First distance to CX (mm), mean ± SD      20.00 ± 5.29   Second distance to CX (mm), mean ± SD      37.82 ± 5.83   Residual LAA volume (ml), mean ± SD      3.6 ± 1.9  Residual pouch size (TOE)  Intraoperative  2–5 days postoperative  Prior-EP (2–3 months after surgery)  Depth (mm), mean ± SD  11.45 ± 4.88  12.37 ± 6.90  12.94 ± 5.99  Area (cm2), mean ± SD  1.70 ± 0.99  2.17 ± 1.12  2.11 ± 1.05  LAA clip location (CT)   First distance to CX (mm), mean ± SD      20.00 ± 5.29   Second distance to CX (mm), mean ± SD      37.82 ± 5.83   Residual LAA volume (ml), mean ± SD      3.6 ± 1.9  Data from all measurements: 2–5 days after and 2–3 months after surgery. The depth and the residual area of the stump were measured using TOE as described in the Methods section and are shown in Fig. 1. The volume was measured using cardiac computed tomography. CT: computed tomography; CX: circumflex artery; LAA: left atrial appendage; SD: standard deviation; TOE: transoesophageal echocardiography. Prior-EP TOE (TOE 2–3 months after surgery) A prior-EP TOE was performed in all patients, with 26 (65%) patients in sinus rhythm. The devices remained stable without further shifts, leaks or thrombi formation, which was also true in the patient with the documented small shift that was observed during the previous TOE. However, in the patient with the unsuccessfully occluded LAA, a thrombus in the LAA was found. No other thrombi were present in the remaining 39 patients. The measured values are presented in Table 2. An example of a patient with excellent occlusion of the LAA is shown in Fig. 3, and an example of a patient with a typical residual finding (i.e. shallow cul-de-sac) is shown in Fig. 4. The stump was >10 mm in depth in 18 (45%) patients and <10 mm in the remaining 22 (55%) patients. Figure 3: View largeDownload slide An example of a patient with a very successful occlusion of the appendage with no residual stump is shown. (A) Transoesophageal echocardiography and (B and C) cardiac computed tomography. Figure 3: View largeDownload slide An example of a patient with a very successful occlusion of the appendage with no residual stump is shown. (A) Transoesophageal echocardiography and (B and C) cardiac computed tomography. Figure 4: View largeDownload slide An example of a patient with a typical residual stump (i.e. the stump takes the form of a shallow cul-de-sac) is shown. The distal part of the appendage was occluded, and from the proximal part, only a smooth residual stump remained. (A and B) Transoesophageal echocardiography and (C) cardiac computed tomography. Figure 4: View largeDownload slide An example of a patient with a typical residual stump (i.e. the stump takes the form of a shallow cul-de-sac) is shown. The distal part of the appendage was occluded, and from the proximal part, only a smooth residual stump remained. (A and B) Transoesophageal echocardiography and (C) cardiac computed tomography. Changes in echocardiographic parameters of the residual pouches over time The measured residual depth and area are presented in Table 2. The overall effect of time on the depth of the residual pouches was statistically non-significant [Wald χ2(2) = 5.48, P = 0.064], although the changes approached statistical significance. Borderline significance was because of the changes between intraoperative values and 2- to 5- day postoperative values and between intraoperative values and prior-EP values. The 2- to 5- day postoperative values and prior-EP values were very similar (P = 0.21). The overall effect of time on the measured area of the residual pouches was statistically significant [Wald χ2(2) = 16.51, P < 0.001]. A detailed analysis found that the changes were due to the difference in the intraoperative values and 2- to 5- day postoperative values (difference estimate = 0.42, 95% confidence interval 0.16–0.68; P = 0.001) and the difference in the intraoperative values and prior-EP values (difference estimate = 0.39, 95% confidence interval 0.18–0.60; P < 0.001). No differences were present between the 2 and 5 days postoperative values and prior-EP values (difference estimate = −0.03, 95% confidence interval 0.29–0.23, P = 0.82). Thus, compared with intraoperative measurements, the depths and areas measured postoperatively both early and later were slightly deeper (or larger). After a 2–5-day window had passed, the values remained stable and unchanged. Cardiac computed tomography findings Cardiac CT was performed in 27 patients, but was refused by 13 patients. The mean volume of the residual pouch was 3.6 ± 1.9 ml. The distance from the CA to the proximal end of the clip was 20.00 ± 5.29 mm (range 10–31 mm), and the distance from the CA to the distal end of the clip was 37.82 ± 5.83 mm (range 28–50 mm). Values measured using cardiac CT are presented in Table 2. The malposition of the AtriClip was confirmed in the patient with the unsuccessful occlusion of the LAA. In the remaining patients, no other unexpected complications were present; additionally, no thrombi formation was observed on CT. Clinical follow-up and current anticoagulation treatment The mean follow-up period was 363.2 ± 205.1 days. No stroke or other systemic cardioembolic events were recorded. Of the 27 patients who were followed up for more than 6 months, OAC was stopped in 19 (70%). DISCUSSION Occlusion of the LAA is commonly performed in patients experiencing AF with concomitant maze, during open-chest surgery or during thoracoscopic ablation for AF. Several different techniques for LAA closure have been developed and consist of either excising, excluding (i.e. closing the orifice into the LAA cavity and leaving the appendage attached) or clipping the LAA. Exclusion of the LAA has often been shown to be incomplete and associated with increased risk of a cardioembolic event. Katz et al. [6] reported incomplete LAA exclusion in 36% of patients (22% of them had a cardioembolic event). Kanderian et al. [14] reported that closures were more often successful after excision (73%) than after exclusion (23%). Three different types of LAA occlusion failure have been described: patent (non-occluded) LAA, residual stump (cul-de-sac) and an unoccluded distal part of the LAA, with persistent flow into the LAA through a narrow channel (‘narrow channel failure’). In Kanderian et al.’s report, patients with residual stumps neither showed signs of thrombi on TOE nor were there any strokes. In contrast, LAA thrombi were present in 46% of patients with ‘narrow channel’ failures. Similar findings were reported by Aryana et al. [7]. During 4 years of follow-up, cardioembolic events occurred in 24% of patients with ‘narrow channel’ failure, while no events were recorded for those with residual stumps. The annual risk of a cardioembolic event for patients with ‘narrow channel’ failure without anticoagulation was nearly 5 times higher than that predicted by the CHA2DS2VASc score. Importantly, a residual stump has never been associated with a higher risk of stroke. Compared with excision or exclusion, limited reports exist describing the procedural efficacy of the occlusion of the LAA using the AtriClip, especially using the thoracoscopic approach, and post-procedural TOE or CT findings. Emmert et al. [13] reported on the first series of implantations of the AtriClip PRO device in 36 patients undergoing open-heart surgery. During the 3 years of follow-up, the AtriClips were found to be stable, with no dislocation and no appendage reperfusion (i.e. ‘narrow channel’ failure). None of the patients had a residual stump >1 cm. However, the report had a huge limitation of complete absence of a methodology regarding how stump depths were measured. Ailawadi et al. [8] studied the short-term procedural efficacy of AtriClip implantation. In a series of 71 patients undergoing cardiac surgery via a median sternotomy, LAA closure using AtriClip was successful in 96% of patients. During the 3 months of follow-up, the clips remained stable and no dislocation was present. No exact measurements of residual stumps were reported. Salzberg et al. [12] observed a cohort of 34 patients in whom the LAA was clipped using the AtriClip during open-chest surgery; 30 of the initial 34 patients were followed up for 3 months, and the placement of the clip was assessed and measured using CT. All clips were placed successfully, and no dislocations or reperfusion of the LAA were documented. The depths of the residual stumps were not reported. In our cohort, in patients who underwent a CT scan, the distances from the left CA to the proximal (20 mm in our patients, 18 mm in Salzberg et al.’s cohort) and distal ends (37 mm in our patients, 34 mm in Salzberg et al.’s cohort) of the clip were only slightly longer compared with Salzberg et al.’s or Emmert et al.’s cohort. In contrast to the aforementioned reports, in which the appendage was occluded during open-chest surgery, all LAA closures in our patients were accomplished using a thoracoscopic approach. Although the thoracoscopic approach is more difficult in terms of device manipulation, the success rate of LAA occlusion using a thoracoscopic approach is similar to that using median sternotomy. Moreover, the rate of complications was very low and included 2 bleeding events associated with the thoracic wall incision; no related sequelae occurred in these patients. Recently, Kurfirst et al. [15] described the efficacy of AtriClip implantation in a mixed (open chest, thoracoscopic) cohort of 101 patients, 56% of whom underwent LAA closure with the AtriClip using a thoracoscopic approach. Ultimately, clip implantation was achieved in 98% of patients. No clip migration, leaks and thrombi formation were observed during the follow-up period, which included TOE and/or CT. Residual LAA stumps >1 cm were present in 2 patients (1.9%); however, and similar to Emmert et al.’s or Ailawadi et al.’s report, no information regarding the measurement of the depth of the stump was given in the methods section. As with other recent studies, appendage reperfusion (i.e. ‘narrow channel’ failure) was not seen in our cohort. This kind of failure has been repeatedly described to be associated with a higher risk of thrombi or strokes after LAA exclusion in the more dated literature; however, there were no reports of this kind of failure after LAA clipping using the AtriClip by Emmert et al., Ailawadi et al., Salzberg et al., Kurfirst et al. and in our study. We found that the immediate intraoperative values (depth and area) were shorter compared with the values obtained 2–5 days, or later, after surgery. This could have been caused by a dilatation of the periostial area of the LA, higher left atrial filling pressure and could have led to false-positive findings immediately after occlusion. Importantly, no further increase in the depth or in the area was observed later on; the values obtained 2–5 days after surgery remained stable and therefore could present a ‘chronic’ state after the occlusion of the LAA. Only 1 (2.5%) patient in our study had an LAA that remained unoccluded because of the malposition of the clip. The patient later experienced a thrombus in the LAA. Based on recent findings, thoracoscopic ablation without heparin and LAA closure is associated with a higher risk of thrombus formation in the LAA [11]. Malpositioning of the clip, i.e. technical or surgical failures, should be eliminated from this procedure. Even in ‘difficult’ cases that may include difficult anatomical conditions or large or multilobar appendages, a good acute effect should be achievable through compliance with sound procedural rules. The clip should be positioned as much as possible at the base of the LAA. The distal end of the clip should be pushed (bent) towards the pulmonary artery or sometimes below it, so that it can be positioned in the same plane as the ostium of the LAA. Careful TOE examination must be done before removing the frame. Slipping of the clip early after deployment (especially if there is pressure on the clip while removing the clip frame) can be prevented by holding down the clip with forceps while lifting the frame off to avoid its movement. Getting familiar with such tips and tricks should be included in training exercises. Unfortunately, there is a possibility that the clip in that 1 patient from our cohort was malpositioned. Closure of the LAA was successful in all other patients of our cohort, with only residual stumps being present on TOE or CT. In a detailed analysis, the stump was <10 mm in depth in 22 (55%) patients. In the literature, a residual stump <10 mm is usually considered a successful occlusion. However, no reports have shown that stumps deeper than 10 mm were associated with an increased risk of stroke, and, furthermore, no suggested methodology for measuring the depth of the stump has ever been published. In our cohort, the depth of the stump was measured as the distance between a plane defined by the top of the Coumadin ridge and the mid-CA to the deepest part of the LAA stump. This methodology was chosen because of its reproducibility: the plane of the ostium is defined by clear anatomical structures. However, it should be emphasized that this methodology is very strict and a depth of 0 mm is unachievable. Even in the best cases, the depth of the stump was never <5 mm. CONCLUSIONS The procedural efficacy of thoracoscopic occlusion of the LAA used in our study was similar to the efficacy obtained during open-chest surgery. No reperfusion of the appendage (‘narrow channel’ failure) was observed, suggesting a very good procedural efficacy of the AtriClip. The association between the depth of the residual stump and the risk of a cardioembolic event needs to be established. For this reason, a standard methodology for measuring the residual stumps should be used in all studies. Our study could serve as an example of how residual stump measurements, following the occlusion of the appendage, could be determined. Funding The study was supported by a research grant from the Ministry of Health of the Czech Republic [grant number AZV 16-32478A]. Conflict of interest: none declared. REFERENCES 1 Zoni-Berisso M, Filippi A, Landolina M, Brignoli O, D’Ambrosio G, Maglia G. Frequency, patient characteristics, treatment strategies, and resource usage of atrial fibrillation (from the Italian Survey of Atrial Fibrillation Management [ISAF] study). Am J Cardiol  2013; 111: 705– 11. Google Scholar CrossRef Search ADS PubMed  2 Kannel WB, Wolf PA, Benjamin EJ, Levy D. Prevalence, incidence, prognosis, and predisposing conditions for atrial fibrillation: population-based estimates. Am J Cardiol  1998; 82: 2N– 9N. Google Scholar CrossRef Search ADS PubMed  3 Stoddard MF, Dawkins PR, Prince CR, Ammash NM. Left atrial appendage thrombus is not uncommon in patients with acute atrial fibrillation and a recent embolic event: a transesophageal echocardiographic study. J Am Coll Cardiol  1995; 25: 452– 9. Google Scholar CrossRef Search ADS PubMed  4 Holmes DR, Reddy VY, Turi ZG, Doshi SK, Sievert H, Buchbinder M et al.  . Percutaneous closure of the left atrial appendage versus warfarin therapy for prevention of stroke in patients with atrial fibrillation: a randomised non-inferiority trial. Lancet  2009; 374: 534– 42. Google Scholar CrossRef Search ADS PubMed  5 Blackshear JL, Odell JA. Appendage obliteration to reduce stroke in cardiac surgical patients with atrial fibrillation. Ann Thorac Surg  1996; 61: 755– 9. Google Scholar CrossRef Search ADS PubMed  6 Katz ES, Tsiamtsiouris T, Applebaum RM, Schwartzbard A, Tunick PA, Kronzon I. Surgical left atrial appendage ligation is frequently incomplete: a transesophageal echocardiograhic study. J Am Coll Cardiol  2000; 36: 468– 71. Google Scholar CrossRef Search ADS PubMed  7 Aryana A, Singh SK, Singh SM, Gearoid O’Neill P, Bowers MR, Allen SL et al.  . Association between incomplete surgical ligation of left atrial appendage and stroke and systemic embolization. Heart Rhythm  2015; 12: 1431– 7. Google Scholar CrossRef Search ADS PubMed  8 Ailawadi G, Gerdisch MW, Harvey RL, Hooker RL, Damiano RJJr, Salamon T et al.  . Exclusion of the left atrial appendage with a novel device: early results of a multicenter trial. J Thorac Cardiovasc Surg  2011; 142: 1002– 9, 1009.e1. Google Scholar CrossRef Search ADS PubMed  9 Osmancik P, Budera P, Zdarska J, Herman D, Petr R, Straka Z. Electrophysiological findings after surgical thoracoscopic atrial fibrillation ablation. Heart Rhythm  2016; 13: 1246– 52. Google Scholar CrossRef Search ADS PubMed  10 Calkins H, Kuck KH, Cappato R, Brugada J, Camm AJ, Chen SA et al.  . 2012 HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design. Europace  2012; 14: 528– 606. Google Scholar CrossRef Search ADS PubMed  11 Budera P, Osmancik P, Herman D, Talavera D, Petr R, Straka Z. Risk of intraatrial thrombi after thoracoscopic ablation in absence of heparin and appendage closure. Ann Thorac Surg  2017; 104: 790– 6. Google Scholar CrossRef Search ADS PubMed  12 Salzberg SP, Plass A, Emmert MY, Desbiolles L, Alkadhi H, Grunenfelder J et al.  . Left atrial appendage clip occlusion: early clinical results. J Thorac Cardiovasc Surg  2010; 139: 1269– 74. Google Scholar CrossRef Search ADS PubMed  13 Emmert MY, Puippe G, Baumuller S, Alkadhi H, Landmesser U, Plass A et al.  . Safe, effective and durable epicardial left atrial appendage clip occlusion in patients with atrial fibrillation undergoing cardiac surgery: first long-term results from a prospective device trial. Eur J Cardiothorac Surg  2014; 45: 126– 31. Google Scholar CrossRef Search ADS PubMed  14 Kanderian AS, Gillinov AM, Pettersson GB, Blackstone E, Klein AL. Success of surgical left atrial appendage closure: assessment by transesophageal echocardiography. J Am Coll Cardiol  2008; 52: 924– 9. Google Scholar CrossRef Search ADS PubMed  15 Kurfirst V, Mokráček A, Čanádyová J, Frána R, Zeman P. Epicardial clip occlusion of the left atrial appendage during cardiac surgery provides optimal surgical results and long-term stability. Interact CardioVasc Thorac Surg  2017; 25: 37– 40. Google Scholar CrossRef Search ADS PubMed  © The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices) http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Interactive CardioVascular and Thoracic Surgery Oxford University Press

Residual echocardiographic and computed tomography findings after thoracoscopic occlusion of the left atrial appendage using the AtriClip PRO device

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Oxford University Press
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© The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
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1569-9293
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1569-9285
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10.1093/icvts/ivx427
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Abstract

Abstract OBJECTIVES Thoracoscopic occlusion of the left atrial appendage (LAA) has become a routine part of thoracoscopic ablation for the treatment of atrial fibrillation (AF). Evaluation of residual findings of the occluded LAA by echocardiography has yet to be described. METHODS Patients with AF indicated for hybrid ablation (thoracoscopic procedure followed by catheter ablation) were enrolled in this study. LAA was occluded as a routine part of the thoracoscopic procedure. Follow-up transoesophageal echocardiography was performed at the end of the procedure, 2–5 days and 2–3 months after the procedure (before the endocardial stage). The residual pouches of the LAA were measured in the mitral valve view (30–110°) and in the perpendicular view. The depth of the residual pouch was measured from the ostial plane (connecting the Coumadin ridge and the circumflex artery) to the deepest part of the residuum. The volume of the residual pouch and the distance from the circumflex artery to the proximal and the distal ends of the AtriClip were measured using computed tomography. RESULTS Forty patients were enrolled in this study. The success rate for the occlusion of the LAA, assessed on transoesophageal echocardiography 2–5 days after surgery, was 97.5%. Regarding the residual findings, no reperfused LAAs were found, and only residual stumps remained. The depth of the stump was 12.9 ± 5.9 mm, the area was 2.2 ± 1.1 cm2, and the volume was 3.6 ± 1.9 ml (all data are shown as mean ± standard deviation). CONCLUSIONS The occlusion of the LAA using an AtriClip PRO device was a clinically safe procedure with high efficacy and was associated with the presence of a small residual pouch after occlusion. Clinical trial registration NCT02832206. Left atrial appendage, Occlusion, Stroke prevention, AtriClip PRO, Hybrid ablation INTRODUCTION Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia with a prevalence of 1–2% in the general population [1]. AF is associated with a 5-fold increased risk of a cardioembolic event [2]. The source of an embolic event is a thrombus, which can form in the left atrium (LA). According to data from autopsies and findings from transoesophageal echocardiography (TOE) in AF patients, approximately 90% of all left atrial thrombi arise in the left atrial appendage (LAA) [3]. In addition to oral anticoagulation (OAC), occlusion of the LAA has become the main non-pharmacological option for the prevention of cardioembolic events. Percutaneous catheter-based techniques for LAA occlusion (using a Watchman device) have been shown to be non-inferior to warfarin in prospective randomized trials [4]. Surgical closure of the LAA has been practised since 1948, primarily in patients with mitral valve disease [5]. It has been proposed that closure of the LAA decreases the risk for stroke in patients with AF, without the need for long-term anticoagulation. The rationale for this procedure is clear; however, several studies have documented frequent incomplete LAA closures, varying between 36% and 60% [6]. Moreover, some types of incomplete closures were associated with significantly higher risks of cardioembolic events than the risk predicted by the CHA2DS2VASc score [7]. Recently, occlusion of the LAA by clipping, using an external device (AtriClip® PRO, AtriCure, Inc., Cincinnati, OH, USA), was described [8]. The device can be used for epicardial clipping of the LAA during open-chest surgery or during thoracoscopic surgery (performed solely to clip the appendage or as a part of a minimally invasive thoracoscopic ablation for AF). Several reports assessing the procedural efficacy and stability of the device during follow-up have been published, with very promising results. However, the exact residual echocardiographic or computed tomographic (CT) findings of the LAA following LAA clipping, as reported for LAA excision and exclusion, are yet to be published. The goal of this study was to describe the procedural and post-procedural efficacy of thoracoscopic occlusion of the LAA (with AtriClips) and to describe residual echocardiographic and CT findings following LAA occlusion. Our other goal was to show the measured parameters in different time periods after occlusion to test whether there were any changes, with time, relative to the depth of the residual pouches after occlusion. METHODS Patients with AF indicated for hybrid ablation were studied. The inclusion and exclusion criteria, as well as project protocol, were previously published in detail elsewhere [9]. In brief, inclusion criteria were symptomatic, non-paroxysmal AF and the absence of significant structural, valvular or coronary heart disease. Exclusion criteria were AF secondary to a reversible condition or known severe pericardial adhesions. Other risk factors (age, comorbidities, LA diameter, AF duration, etc.) were assessed individually after a thorough discussion of the risks among the members of an informal AF team, comprising the cardiac surgeon, anaesthetist and electrophysiologist, and with the patient. AF types and definition of success were designed in accordance with actual recommendations [10], and the project was approved by the institutional ethics committee. All patients provided written informed consent. Surgical procedure A fully thoracoscopic, two-sided, off-pump, epicardial approach was used for the surgical ablation and LAA occlusion, as described in detail elsewhere [11]. The first part of the procedure, i.e. ablation of the posterior LA (‘box lesion’), was performed through a right thoracoscopy. During the procedure, a circumferential lesion was created anterior to the pulmonary veins with the goal of isolating all pulmonary veins and the posterior LA en bloc (the ‘box-lesion’ set). Lesions were created using a unipolar/bipolar linear radiofrequency COBRA Fusion™ 150 (Estech, an AtriCure® Company, San Ramon, CA, USA) catheter. If a patient remained in AF, a direct current cardioversion was performed. After ablation through the right chest had been performed, occlusion of the LAA, via a left thoracoscopy, was carried out using the AtriClip PRO device (AtriCure, Inc.). Single-lung ventilation was switched to the right side and the left hemithorax was entered with 3 working ports (third, fourth and sixth intercostal space). The pericardium was opened dorsally from the phrenic nerve. Next, the base of the LAA was measured, and the AtriClip PRO device was inserted via the inferior incision (which had to be enlarged to about 6 cm in length first) and carefully placed at the base of the LAA, with the goal of placing the device as close as possible to the bottom of the LAA, without covering the circumflex artery (CA). After closure of the clip, the position was checked using TOE: the goal was to create a residual pouch <10 mm in depth. When both the surgeon and the echocardiographer were satisfied with the position of the device, the AtriClip was released and the deploying system withdrawn from the thorax. Bleeding was staunched, and one drain was inserted prior to chest closure. Because the procedure was performed immediately after the completion of the thoracoscopic ablation, both procedures were done on heparin with a target activated clotting time (ACT) >300–350 s. For 2 h after surgery, patients received a continuous infusion of heparin with a target ACT of 180–200 s. Starting on the morning after surgery, patients were given low-molecular-weight heparin until effective OAC was achieved. OAC was continued for at least 3 months after surgery. Transoesophageal echocardiography Three TOE examinations were performed in all patients. The first examination was performed in the operating room before and during the thoracoscopic procedure. Before the procedure, the LAA was checked for thrombi formation, and LAA dimensions (ostium and landing zone) were measured. Moreover, attachment of the AtriClip (occlusion of the LAA) was carried out under TOE guidance. The second TOE was performed 2–5 days after surgery and the third TOE 2–3 months after surgery (prior-EP TOE). The goals were to check the position of the AtriClip PRO device, check for the presence of thrombi formation on the device and measure the residual pouch of the LAA. During all post-procedural TOE examinations, the morphology and size of the residual pouch of the LAA were assessed. The LAA pouch was visualized using different TOE probe angles. Measurements were made using the probe angle that offered the largest visualizable LAA pouch (typically between 30° and 90°). The ostium of the LAA was measured as the distance between the mid-CA and the top of the Coumadin ridge (i.e. the ridge between the left upper pulmonary vein and the LAA). The depth of the residual pouch was measured as the distance from the deepest part of the pouch to the plane of the ostium. The area of the pouch was measured as the area below the plane of the ostium. An example of the measurement of the LAA pouch is shown in Fig. 1. Figure 1: View largeDownload slide An example of the measurement of the residual stump after the occlusion of the appendage. First, a line was drawn connecting the ostium of the appendage, i.e. a line from the mid-circumflex artery to the top of the ridge between the left superior pulmonary vein and the appendage. Then, the depth of the stump was measured by dropping a perpendicular line from the aforementioned line to the deepest part of the appendage. Figure 1: View largeDownload slide An example of the measurement of the residual stump after the occlusion of the appendage. First, a line was drawn connecting the ostium of the appendage, i.e. a line from the mid-circumflex artery to the top of the ridge between the left superior pulmonary vein and the appendage. Then, the depth of the stump was measured by dropping a perpendicular line from the aforementioned line to the deepest part of the appendage. Cardiac computed tomography CT imaging was taken 2–5 months after the surgical procedure using a 256-detector row CT scanner (Brilliance iCT 256; Philips, Best, Netherlands). A triphasic injection of 60 ml of contrast media (Ultravist 370; Bayer Healthcare Pharmaceuticals, Montville, NJ, USA) was used. The first 50 ml of contrast agent was administered at a flow rate of 4.0 ml/s, followed by 20 ml of a 50/50 mixture of contrast and saline. Subsequently, a 30 ml saline flush was administered at a flow rate of 3.0 ml/s. Bolus tracking was used for synchronization of the contrast medium injection with scanning. The region of interest was positioned over the descending aorta. After the enhancement reached 140 HU, there was a 3-s post-threshold delay before the scan was commenced. Prospective electrocardiographic-triggered dose modulation (mode ‘step and shoot’) was the preferred method, using scanning at 70–80% of the RR interval. Image post-processing Data sets were transferred to an external workstation (Comprehensive Cardiac Analyses, Brilliance Workspace version 4.0; Philips Healthcare, Cleveland, OH, USA) for offline analysis. Axial slices, oblique reconstructions and maximum intensity projection images were used. For calculating the volume of the LAA pouch, 3-mm slices were used. Each slice of the LAA pouch was identified, and the borders were manually traced for volume assessment. In addition, the ostium of the left CA was identified and the distance to the end of the clip was measured, as suggested by Salzberg and Emmert [12, 13]. Statistical analysis Data from this study were tabulated using descriptive statistics. Continuous variables were presented as means and standard deviations (in a format mean ± SD), and categorical variables were presented as absolute and relative frequencies. The Shapiro–Wilk test was used to assess whether data were drawn from a normal distribution. To test the hypothesis that there were no changes in the investigated characteristics (depth and area) over time, a linear random-effects model was applied. Huber–White robust estimates of the standard errors were used to account for potential heteroscedasticity of errors. In cases with significant between-time differences, pairwise comparisons were done with Sidak’s correction for multiple testing. All tests were evaluated at a significance level of 0.05. All statistical analyses were done using Stata software, version 14.1 (Stata Corporation, College Station, TX, USA). RESULTS Patients and surgery Forty patients were enrolled in this prospective, observational study. The time frame for enrolment was from May 2015 to April 2017. Baseline clinical characteristics are presented in Table 1. Mean surgical time was 159.8 ± 27.6 min (including the previously performed left-sided thoracoscopic ablation), and the mean hospital stay was 7.7 ± 5.1 days. The device sizes used most often were 35 mm (implanted in 27 patients), followed by 40 mm (12 patients) and 45 mm (1 patient). The mean size of the ostium of the LAA before the implantation was 21.7 ± 3.7 mm. The devices were deployed in all patients. Table 1: Baseline patient characteristics Variables  Age (years), mean ± SD  62.6 ± 8.6  Male gender, n (%)  23 (57.5)  BMI (kg/m2), mean ± SD  30.3 ± 5.1  Hypertension, n (%)  21 (52.5)  Congestive heart failure (LVEF ≤40%), n (%)  10 (25)  Diabetes mellitus (%), n (%)  9 (22.5)  Stroke or TIA (%), n (%)  8 (20)  History of PCI (%), n (%)  1 (2.5)  CHA2DS2VASc score, mean ± SD  2.2 ± 1.47  LA diameter (mm) , mean ± SD  44.9 ± 8.8  LVEF (%), mean ± SD  52.3 ± 12.3  LVEDD (mm), mean ± SD  53.4 ± 4.8  Persistent AF, n (%)  14 (35)  LSPe AF  26 (65)  Variables  Age (years), mean ± SD  62.6 ± 8.6  Male gender, n (%)  23 (57.5)  BMI (kg/m2), mean ± SD  30.3 ± 5.1  Hypertension, n (%)  21 (52.5)  Congestive heart failure (LVEF ≤40%), n (%)  10 (25)  Diabetes mellitus (%), n (%)  9 (22.5)  Stroke or TIA (%), n (%)  8 (20)  History of PCI (%), n (%)  1 (2.5)  CHA2DS2VASc score, mean ± SD  2.2 ± 1.47  LA diameter (mm) , mean ± SD  44.9 ± 8.8  LVEF (%), mean ± SD  52.3 ± 12.3  LVEDD (mm), mean ± SD  53.4 ± 4.8  Persistent AF, n (%)  14 (35)  LSPe AF  26 (65)  AF: atrial fibrillation; BMI: body mass index; LA: left atrium; LVEDD: left ventricular end-diastolic diameter; LVEF: left ventricular ejection fraction; LSPe: long-standing persistent; PCI: percutaneous coronary intervention; SD: standard deviation; TIA: transient ischaemic attack. Table 1: Baseline patient characteristics Variables  Age (years), mean ± SD  62.6 ± 8.6  Male gender, n (%)  23 (57.5)  BMI (kg/m2), mean ± SD  30.3 ± 5.1  Hypertension, n (%)  21 (52.5)  Congestive heart failure (LVEF ≤40%), n (%)  10 (25)  Diabetes mellitus (%), n (%)  9 (22.5)  Stroke or TIA (%), n (%)  8 (20)  History of PCI (%), n (%)  1 (2.5)  CHA2DS2VASc score, mean ± SD  2.2 ± 1.47  LA diameter (mm) , mean ± SD  44.9 ± 8.8  LVEF (%), mean ± SD  52.3 ± 12.3  LVEDD (mm), mean ± SD  53.4 ± 4.8  Persistent AF, n (%)  14 (35)  LSPe AF  26 (65)  Variables  Age (years), mean ± SD  62.6 ± 8.6  Male gender, n (%)  23 (57.5)  BMI (kg/m2), mean ± SD  30.3 ± 5.1  Hypertension, n (%)  21 (52.5)  Congestive heart failure (LVEF ≤40%), n (%)  10 (25)  Diabetes mellitus (%), n (%)  9 (22.5)  Stroke or TIA (%), n (%)  8 (20)  History of PCI (%), n (%)  1 (2.5)  CHA2DS2VASc score, mean ± SD  2.2 ± 1.47  LA diameter (mm) , mean ± SD  44.9 ± 8.8  LVEF (%), mean ± SD  52.3 ± 12.3  LVEDD (mm), mean ± SD  53.4 ± 4.8  Persistent AF, n (%)  14 (35)  LSPe AF  26 (65)  AF: atrial fibrillation; BMI: body mass index; LA: left atrium; LVEDD: left ventricular end-diastolic diameter; LVEF: left ventricular ejection fraction; LSPe: long-standing persistent; PCI: percutaneous coronary intervention; SD: standard deviation; TIA: transient ischaemic attack. Regarding complications, 2 patients had to undergo surgical revision due to procedure-related bleeding. In both cases, the source of bleeding was the thoracic wall incision on the left side (i.e. the bleeding was assessed as procedure related). No bleeding complications stemming directly from the use of the AtriClip device (i.e. bleeding due to LA or LAA laceration) were noted. One of the 2 revision patients developed respiratory insufficiency, which required prolonged mechanical ventilation after the revision. Intraoperative transoesophageal echocardiography Careful checking of the devices at the end of the procedure revealed an LAA occlusion failure in 1 patient (Fig. 2). Despite what appeared to be proper device positioning, based on optical visualization using a camera, and adequate closure (as observed on TOE), the TOE at the end of the procedure revealed that the LAA was left almost completely open. The malposition of the Atriclip was later confirmed on cardiac CT (Fig. 2). In this patient, the depth of the residual pouch was 33 mm, and the area was 3.5 cm2. All other devices were implanted successfully with a mean depth of 11.45 ± 4.88 mm and an area of 1.70 ± 0.99 cm2. No leaks (‘narrow channel kind’ of failure) or thrombi were present at the end of surgery. Figure 2: View largeDownload slide An example of a patient with an unsuccessful occlusion of the left atrial appendage is shown. The AtriClip was placed very distally, and a large residual stump remained. (A and B) Transoesophagel echocardiography and (C and D) cardiac computed tomography. Figure 2: View largeDownload slide An example of a patient with an unsuccessful occlusion of the left atrial appendage is shown. The AtriClip was placed very distally, and a large residual stump remained. (A and B) Transoesophagel echocardiography and (C and D) cardiac computed tomography. Postoperative transoesophageal echocardiography (2–5 days after surgery) During the postoperative TOE, 1 patient was found to have a small shift of the device. The device shifted distally, and the depth of the pouch increased from 8 mm to 16 mm; similarly the area increased from 1.3 cm2 to 2.7 cm2. However, the distal trabeculated part of the appendage remained occluded, and only the residual smooth cul-de-sac portion of the proximal part of the appendage was shown on TOE, and it was of similar depth as that observed in other patients. Therefore, this shift was not assessed as a failure. The position of the device in all other patients remained stable, and no leaks or thrombi in the LAA pouch were detected. The depths and areas of residual stumps are presented in Table 2. The final efficacy was 97.5%, after including 1 patient with occlusion failure during surgery. Table 2: Data from all measurements Residual pouch size (TOE)  Intraoperative  2–5 days postoperative  Prior-EP (2–3 months after surgery)  Depth (mm), mean ± SD  11.45 ± 4.88  12.37 ± 6.90  12.94 ± 5.99  Area (cm2), mean ± SD  1.70 ± 0.99  2.17 ± 1.12  2.11 ± 1.05  LAA clip location (CT)   First distance to CX (mm), mean ± SD      20.00 ± 5.29   Second distance to CX (mm), mean ± SD      37.82 ± 5.83   Residual LAA volume (ml), mean ± SD      3.6 ± 1.9  Residual pouch size (TOE)  Intraoperative  2–5 days postoperative  Prior-EP (2–3 months after surgery)  Depth (mm), mean ± SD  11.45 ± 4.88  12.37 ± 6.90  12.94 ± 5.99  Area (cm2), mean ± SD  1.70 ± 0.99  2.17 ± 1.12  2.11 ± 1.05  LAA clip location (CT)   First distance to CX (mm), mean ± SD      20.00 ± 5.29   Second distance to CX (mm), mean ± SD      37.82 ± 5.83   Residual LAA volume (ml), mean ± SD      3.6 ± 1.9  Data from all measurements: 2–5 days after and 2–3 months after surgery. The depth and the residual area of the stump were measured using TOE as described in the Methods section and are shown in Fig. 1. The volume was measured using cardiac computed tomography. CT: computed tomography; CX: circumflex artery; LAA: left atrial appendage; SD: standard deviation; TOE: transoesophageal echocardiography. Table 2: Data from all measurements Residual pouch size (TOE)  Intraoperative  2–5 days postoperative  Prior-EP (2–3 months after surgery)  Depth (mm), mean ± SD  11.45 ± 4.88  12.37 ± 6.90  12.94 ± 5.99  Area (cm2), mean ± SD  1.70 ± 0.99  2.17 ± 1.12  2.11 ± 1.05  LAA clip location (CT)   First distance to CX (mm), mean ± SD      20.00 ± 5.29   Second distance to CX (mm), mean ± SD      37.82 ± 5.83   Residual LAA volume (ml), mean ± SD      3.6 ± 1.9  Residual pouch size (TOE)  Intraoperative  2–5 days postoperative  Prior-EP (2–3 months after surgery)  Depth (mm), mean ± SD  11.45 ± 4.88  12.37 ± 6.90  12.94 ± 5.99  Area (cm2), mean ± SD  1.70 ± 0.99  2.17 ± 1.12  2.11 ± 1.05  LAA clip location (CT)   First distance to CX (mm), mean ± SD      20.00 ± 5.29   Second distance to CX (mm), mean ± SD      37.82 ± 5.83   Residual LAA volume (ml), mean ± SD      3.6 ± 1.9  Data from all measurements: 2–5 days after and 2–3 months after surgery. The depth and the residual area of the stump were measured using TOE as described in the Methods section and are shown in Fig. 1. The volume was measured using cardiac computed tomography. CT: computed tomography; CX: circumflex artery; LAA: left atrial appendage; SD: standard deviation; TOE: transoesophageal echocardiography. Prior-EP TOE (TOE 2–3 months after surgery) A prior-EP TOE was performed in all patients, with 26 (65%) patients in sinus rhythm. The devices remained stable without further shifts, leaks or thrombi formation, which was also true in the patient with the documented small shift that was observed during the previous TOE. However, in the patient with the unsuccessfully occluded LAA, a thrombus in the LAA was found. No other thrombi were present in the remaining 39 patients. The measured values are presented in Table 2. An example of a patient with excellent occlusion of the LAA is shown in Fig. 3, and an example of a patient with a typical residual finding (i.e. shallow cul-de-sac) is shown in Fig. 4. The stump was >10 mm in depth in 18 (45%) patients and <10 mm in the remaining 22 (55%) patients. Figure 3: View largeDownload slide An example of a patient with a very successful occlusion of the appendage with no residual stump is shown. (A) Transoesophageal echocardiography and (B and C) cardiac computed tomography. Figure 3: View largeDownload slide An example of a patient with a very successful occlusion of the appendage with no residual stump is shown. (A) Transoesophageal echocardiography and (B and C) cardiac computed tomography. Figure 4: View largeDownload slide An example of a patient with a typical residual stump (i.e. the stump takes the form of a shallow cul-de-sac) is shown. The distal part of the appendage was occluded, and from the proximal part, only a smooth residual stump remained. (A and B) Transoesophageal echocardiography and (C) cardiac computed tomography. Figure 4: View largeDownload slide An example of a patient with a typical residual stump (i.e. the stump takes the form of a shallow cul-de-sac) is shown. The distal part of the appendage was occluded, and from the proximal part, only a smooth residual stump remained. (A and B) Transoesophageal echocardiography and (C) cardiac computed tomography. Changes in echocardiographic parameters of the residual pouches over time The measured residual depth and area are presented in Table 2. The overall effect of time on the depth of the residual pouches was statistically non-significant [Wald χ2(2) = 5.48, P = 0.064], although the changes approached statistical significance. Borderline significance was because of the changes between intraoperative values and 2- to 5- day postoperative values and between intraoperative values and prior-EP values. The 2- to 5- day postoperative values and prior-EP values were very similar (P = 0.21). The overall effect of time on the measured area of the residual pouches was statistically significant [Wald χ2(2) = 16.51, P < 0.001]. A detailed analysis found that the changes were due to the difference in the intraoperative values and 2- to 5- day postoperative values (difference estimate = 0.42, 95% confidence interval 0.16–0.68; P = 0.001) and the difference in the intraoperative values and prior-EP values (difference estimate = 0.39, 95% confidence interval 0.18–0.60; P < 0.001). No differences were present between the 2 and 5 days postoperative values and prior-EP values (difference estimate = −0.03, 95% confidence interval 0.29–0.23, P = 0.82). Thus, compared with intraoperative measurements, the depths and areas measured postoperatively both early and later were slightly deeper (or larger). After a 2–5-day window had passed, the values remained stable and unchanged. Cardiac computed tomography findings Cardiac CT was performed in 27 patients, but was refused by 13 patients. The mean volume of the residual pouch was 3.6 ± 1.9 ml. The distance from the CA to the proximal end of the clip was 20.00 ± 5.29 mm (range 10–31 mm), and the distance from the CA to the distal end of the clip was 37.82 ± 5.83 mm (range 28–50 mm). Values measured using cardiac CT are presented in Table 2. The malposition of the AtriClip was confirmed in the patient with the unsuccessful occlusion of the LAA. In the remaining patients, no other unexpected complications were present; additionally, no thrombi formation was observed on CT. Clinical follow-up and current anticoagulation treatment The mean follow-up period was 363.2 ± 205.1 days. No stroke or other systemic cardioembolic events were recorded. Of the 27 patients who were followed up for more than 6 months, OAC was stopped in 19 (70%). DISCUSSION Occlusion of the LAA is commonly performed in patients experiencing AF with concomitant maze, during open-chest surgery or during thoracoscopic ablation for AF. Several different techniques for LAA closure have been developed and consist of either excising, excluding (i.e. closing the orifice into the LAA cavity and leaving the appendage attached) or clipping the LAA. Exclusion of the LAA has often been shown to be incomplete and associated with increased risk of a cardioembolic event. Katz et al. [6] reported incomplete LAA exclusion in 36% of patients (22% of them had a cardioembolic event). Kanderian et al. [14] reported that closures were more often successful after excision (73%) than after exclusion (23%). Three different types of LAA occlusion failure have been described: patent (non-occluded) LAA, residual stump (cul-de-sac) and an unoccluded distal part of the LAA, with persistent flow into the LAA through a narrow channel (‘narrow channel failure’). In Kanderian et al.’s report, patients with residual stumps neither showed signs of thrombi on TOE nor were there any strokes. In contrast, LAA thrombi were present in 46% of patients with ‘narrow channel’ failures. Similar findings were reported by Aryana et al. [7]. During 4 years of follow-up, cardioembolic events occurred in 24% of patients with ‘narrow channel’ failure, while no events were recorded for those with residual stumps. The annual risk of a cardioembolic event for patients with ‘narrow channel’ failure without anticoagulation was nearly 5 times higher than that predicted by the CHA2DS2VASc score. Importantly, a residual stump has never been associated with a higher risk of stroke. Compared with excision or exclusion, limited reports exist describing the procedural efficacy of the occlusion of the LAA using the AtriClip, especially using the thoracoscopic approach, and post-procedural TOE or CT findings. Emmert et al. [13] reported on the first series of implantations of the AtriClip PRO device in 36 patients undergoing open-heart surgery. During the 3 years of follow-up, the AtriClips were found to be stable, with no dislocation and no appendage reperfusion (i.e. ‘narrow channel’ failure). None of the patients had a residual stump >1 cm. However, the report had a huge limitation of complete absence of a methodology regarding how stump depths were measured. Ailawadi et al. [8] studied the short-term procedural efficacy of AtriClip implantation. In a series of 71 patients undergoing cardiac surgery via a median sternotomy, LAA closure using AtriClip was successful in 96% of patients. During the 3 months of follow-up, the clips remained stable and no dislocation was present. No exact measurements of residual stumps were reported. Salzberg et al. [12] observed a cohort of 34 patients in whom the LAA was clipped using the AtriClip during open-chest surgery; 30 of the initial 34 patients were followed up for 3 months, and the placement of the clip was assessed and measured using CT. All clips were placed successfully, and no dislocations or reperfusion of the LAA were documented. The depths of the residual stumps were not reported. In our cohort, in patients who underwent a CT scan, the distances from the left CA to the proximal (20 mm in our patients, 18 mm in Salzberg et al.’s cohort) and distal ends (37 mm in our patients, 34 mm in Salzberg et al.’s cohort) of the clip were only slightly longer compared with Salzberg et al.’s or Emmert et al.’s cohort. In contrast to the aforementioned reports, in which the appendage was occluded during open-chest surgery, all LAA closures in our patients were accomplished using a thoracoscopic approach. Although the thoracoscopic approach is more difficult in terms of device manipulation, the success rate of LAA occlusion using a thoracoscopic approach is similar to that using median sternotomy. Moreover, the rate of complications was very low and included 2 bleeding events associated with the thoracic wall incision; no related sequelae occurred in these patients. Recently, Kurfirst et al. [15] described the efficacy of AtriClip implantation in a mixed (open chest, thoracoscopic) cohort of 101 patients, 56% of whom underwent LAA closure with the AtriClip using a thoracoscopic approach. Ultimately, clip implantation was achieved in 98% of patients. No clip migration, leaks and thrombi formation were observed during the follow-up period, which included TOE and/or CT. Residual LAA stumps >1 cm were present in 2 patients (1.9%); however, and similar to Emmert et al.’s or Ailawadi et al.’s report, no information regarding the measurement of the depth of the stump was given in the methods section. As with other recent studies, appendage reperfusion (i.e. ‘narrow channel’ failure) was not seen in our cohort. This kind of failure has been repeatedly described to be associated with a higher risk of thrombi or strokes after LAA exclusion in the more dated literature; however, there were no reports of this kind of failure after LAA clipping using the AtriClip by Emmert et al., Ailawadi et al., Salzberg et al., Kurfirst et al. and in our study. We found that the immediate intraoperative values (depth and area) were shorter compared with the values obtained 2–5 days, or later, after surgery. This could have been caused by a dilatation of the periostial area of the LA, higher left atrial filling pressure and could have led to false-positive findings immediately after occlusion. Importantly, no further increase in the depth or in the area was observed later on; the values obtained 2–5 days after surgery remained stable and therefore could present a ‘chronic’ state after the occlusion of the LAA. Only 1 (2.5%) patient in our study had an LAA that remained unoccluded because of the malposition of the clip. The patient later experienced a thrombus in the LAA. Based on recent findings, thoracoscopic ablation without heparin and LAA closure is associated with a higher risk of thrombus formation in the LAA [11]. Malpositioning of the clip, i.e. technical or surgical failures, should be eliminated from this procedure. Even in ‘difficult’ cases that may include difficult anatomical conditions or large or multilobar appendages, a good acute effect should be achievable through compliance with sound procedural rules. The clip should be positioned as much as possible at the base of the LAA. The distal end of the clip should be pushed (bent) towards the pulmonary artery or sometimes below it, so that it can be positioned in the same plane as the ostium of the LAA. Careful TOE examination must be done before removing the frame. Slipping of the clip early after deployment (especially if there is pressure on the clip while removing the clip frame) can be prevented by holding down the clip with forceps while lifting the frame off to avoid its movement. Getting familiar with such tips and tricks should be included in training exercises. Unfortunately, there is a possibility that the clip in that 1 patient from our cohort was malpositioned. Closure of the LAA was successful in all other patients of our cohort, with only residual stumps being present on TOE or CT. In a detailed analysis, the stump was <10 mm in depth in 22 (55%) patients. In the literature, a residual stump <10 mm is usually considered a successful occlusion. However, no reports have shown that stumps deeper than 10 mm were associated with an increased risk of stroke, and, furthermore, no suggested methodology for measuring the depth of the stump has ever been published. In our cohort, the depth of the stump was measured as the distance between a plane defined by the top of the Coumadin ridge and the mid-CA to the deepest part of the LAA stump. This methodology was chosen because of its reproducibility: the plane of the ostium is defined by clear anatomical structures. However, it should be emphasized that this methodology is very strict and a depth of 0 mm is unachievable. Even in the best cases, the depth of the stump was never <5 mm. CONCLUSIONS The procedural efficacy of thoracoscopic occlusion of the LAA used in our study was similar to the efficacy obtained during open-chest surgery. No reperfusion of the appendage (‘narrow channel’ failure) was observed, suggesting a very good procedural efficacy of the AtriClip. The association between the depth of the residual stump and the risk of a cardioembolic event needs to be established. For this reason, a standard methodology for measuring the residual stumps should be used in all studies. Our study could serve as an example of how residual stump measurements, following the occlusion of the appendage, could be determined. Funding The study was supported by a research grant from the Ministry of Health of the Czech Republic [grant number AZV 16-32478A]. Conflict of interest: none declared. REFERENCES 1 Zoni-Berisso M, Filippi A, Landolina M, Brignoli O, D’Ambrosio G, Maglia G. 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Percutaneous closure of the left atrial appendage versus warfarin therapy for prevention of stroke in patients with atrial fibrillation: a randomised non-inferiority trial. Lancet  2009; 374: 534– 42. Google Scholar CrossRef Search ADS PubMed  5 Blackshear JL, Odell JA. Appendage obliteration to reduce stroke in cardiac surgical patients with atrial fibrillation. Ann Thorac Surg  1996; 61: 755– 9. Google Scholar CrossRef Search ADS PubMed  6 Katz ES, Tsiamtsiouris T, Applebaum RM, Schwartzbard A, Tunick PA, Kronzon I. Surgical left atrial appendage ligation is frequently incomplete: a transesophageal echocardiograhic study. J Am Coll Cardiol  2000; 36: 468– 71. Google Scholar CrossRef Search ADS PubMed  7 Aryana A, Singh SK, Singh SM, Gearoid O’Neill P, Bowers MR, Allen SL et al.  . Association between incomplete surgical ligation of left atrial appendage and stroke and systemic embolization. Heart Rhythm  2015; 12: 1431– 7. Google Scholar CrossRef Search ADS PubMed  8 Ailawadi G, Gerdisch MW, Harvey RL, Hooker RL, Damiano RJJr, Salamon T et al.  . Exclusion of the left atrial appendage with a novel device: early results of a multicenter trial. J Thorac Cardiovasc Surg  2011; 142: 1002– 9, 1009.e1. Google Scholar CrossRef Search ADS PubMed  9 Osmancik P, Budera P, Zdarska J, Herman D, Petr R, Straka Z. Electrophysiological findings after surgical thoracoscopic atrial fibrillation ablation. Heart Rhythm  2016; 13: 1246– 52. Google Scholar CrossRef Search ADS PubMed  10 Calkins H, Kuck KH, Cappato R, Brugada J, Camm AJ, Chen SA et al.  . 2012 HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design. Europace  2012; 14: 528– 606. Google Scholar CrossRef Search ADS PubMed  11 Budera P, Osmancik P, Herman D, Talavera D, Petr R, Straka Z. Risk of intraatrial thrombi after thoracoscopic ablation in absence of heparin and appendage closure. Ann Thorac Surg  2017; 104: 790– 6. Google Scholar CrossRef Search ADS PubMed  12 Salzberg SP, Plass A, Emmert MY, Desbiolles L, Alkadhi H, Grunenfelder J et al.  . Left atrial appendage clip occlusion: early clinical results. J Thorac Cardiovasc Surg  2010; 139: 1269– 74. Google Scholar CrossRef Search ADS PubMed  13 Emmert MY, Puippe G, Baumuller S, Alkadhi H, Landmesser U, Plass A et al.  . Safe, effective and durable epicardial left atrial appendage clip occlusion in patients with atrial fibrillation undergoing cardiac surgery: first long-term results from a prospective device trial. Eur J Cardiothorac Surg  2014; 45: 126– 31. Google Scholar CrossRef Search ADS PubMed  14 Kanderian AS, Gillinov AM, Pettersson GB, Blackstone E, Klein AL. Success of surgical left atrial appendage closure: assessment by transesophageal echocardiography. J Am Coll Cardiol  2008; 52: 924– 9. Google Scholar CrossRef Search ADS PubMed  15 Kurfirst V, Mokráček A, Čanádyová J, Frána R, Zeman P. Epicardial clip occlusion of the left atrial appendage during cardiac surgery provides optimal surgical results and long-term stability. Interact CardioVasc Thorac Surg  2017; 25: 37– 40. Google Scholar CrossRef Search ADS PubMed  © The Author(s) 2018. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

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Interactive CardioVascular and Thoracic SurgeryOxford University Press

Published: Jan 18, 2018

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