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• W2149778877 abstract "HomeCirculationVol. 130, No. 2Left Atrial Appendage Closure to Prevent Stroke in Patients With Atrial Fibrillation Free AccessResearch ArticlePDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessResearch ArticlePDF/EPUBLeft Atrial Appendage Closure to Prevent Stroke in Patients With Atrial Fibrillation Matthew J. Price, MD and Miguel Valderrábano, MD Matthew J. PriceMatthew J. Price From the Scripps Clinic, La Jolla, CA (M.J.P.); and Methodist Hospital, Houston, TX (M.V.). Search for more papers by this author and Miguel ValderrábanoMiguel Valderrábano From the Scripps Clinic, La Jolla, CA (M.J.P.); and Methodist Hospital, Houston, TX (M.V.). Search for more papers by this author Originally published8 Jul 2014https://doi.org/10.1161/CIRCULATIONAHA.114.009060Circulation. 2014;130:202–212Atrial fibrillation (AF) is the most common sustained arrhythmia and is associated with substantial morbidity. The prevalence of AF in the United States is expected to rise to between 5.6 and 12 million in 2050.1 AF is associated with a 4- to 5-fold increased risk of ischemic stroke after adjustment for other risk factors,2 and paroxysmal, persistent, or permanent AF increases stroke risk to a similar degree. Oral anticoagulants (OACs) reduce the risk of thromboembolism, yet they are underused.3–6 Novel OACs are noninferior or superior to warfarin for the prevention of stroke and systemic embolism and are more convenient because they do not require ongoing monitoring.7–10 However, major challenges to long-term therapy with vitamin K antagonists and novel OACs include a substantial ongoing hazard of major bleeding, noncompliance, side effects, and, in the case of the novel OACs, lack of an available antidote. The left atrial appendage (LAA) is the predominant nidus for thrombus formation in AF, and transcatheter LAA closure has emerged as a potential alternative to oral anticoagulation in at-risk AF patients.The LAA and Stroke in AFAF is associated with mechanical dysfunction of atrial tissue. Loss of contractile function in the LAA can lead to local stasis and thrombus formation, which may then embolize into the systemic circulation. The observation that >90% of thrombi found in patients with nonvalvular AF and stroke are in the LAA supports this mechanistic sequence.11 In addition, low Doppler inflow velocities, spontaneous echocardiographic contrast, and the presence of thrombus in the LAA have been associated with high stroke rates in AF patients.12 These data lend support to the hypothesis that the elimination of the LAA may serve as a preventive strategy for AF-related stroke.Morphological features of the LAA may influence stroke risk. Larger LAA neck diameter and LAA depth have been associated with a higher prevalence of prior stroke in AF patients.13 A chicken wing shape appears to correlate less with prior embolic events than cauliflower, cactus, or windsock shapes,14 but although this finding was reproduced in 1 small study,15 it was disputed by another, larger study.16 Such categorization of LAA morphology may be a poorly reproducible oversimplification of anatomy. The extent of trabeculations within the LAA may be a better predictor of thromboembolic events.16 Therefore, LAA characteristics appear to influence stroke risk, but to date, there are no reproducible LAA features sufficiently validated for risk stratification.Stroke risk is influenced by a multitude of factors. Although the LAA is the most common site of thrombus in patients with nonvalvular AF and stroke, thrombi were identified only in the minority of such patients.11 Although the offending thrombi could have embolized before LAA assessment, additional data suggest that not all strokes in AF may be prevented by LAA-targeted therapies. As many as 25% of strokes in AF patients can be linked to intrinsic cerebrovascular disease.17 The CHADS2 and CHA2DS2VASc scores are based on a particular individual’s comorbidities (Tables 1 and 2). They can estimate a yearly risk of thromboembolic events18,19 and identify which patients may derive clinical benefit from anticoagulation,20 yet they do not include parameters of LAA function or anatomy. Although hypertension and aortic atherosclerosis have been associated with an increased prevalence of LAA thrombus, spontaneous contrast, and low LAA inflow velocity,21 the mechanistic connections between the LAA and many risk factors known to be predictive of stroke in AF remain to be fully elucidated. Despite these uncertainties, the LAA is a consistent and predictable site of origin of cerebral and systemic emboli in AF and thus constitutes an opportunity for stroke prophylaxis.Table 1. The CHADS2 Model for Thromboembolic Risk in AFCharacteristicPointsCongestive heart failure1Hypertension1Age ≥75 y1Diabetes mellitus1Stroke or transient ischemic attack2AF indicates atrial fibrillation.Table 2. The CHA2DS2VASC Model for Thromboembolic Risk in AFCharacteristicPointsCongestive heart failure1Hypertension1Age 65–74 y1Age ≥75 y2Diabetes mellitus1Stroke or transient ischemic attack2Vascular disease1Female sex1AF indicates atrial fibrillation.General Concepts for LAA Closure Device EvaluationThe appropriate assessment of transcatheter LAA devices requires a critical evaluation of the types of outcomes studied. Efficacy outcomes may include anatomic efficacy, that is, success of LAA closure on imaging studies, and clinical efficacy, that is, stroke prevention in the absence of oral anticoagulation. Although anatomic closure is commonly used as a surrogate for clinical efficacy, LAA closure may not guarantee long-term efficacy, whereas small residual leaks may not necessarily result in clinical failure.22 Because the mechanism, material, and consequences of closure may differ between devices, clinical efficacy of 1 device may not necessarily translate into clinical efficacy of another device that has been shown to provide only anatomic closure. Safety outcomes are particularly important because LAA closure is a prophylactic procedure. The transcatheter devices share certain types of procedural complications (eg, vascular access bleeding, pericardial effusions, and air embolism), but the rates of complications may differ as a result of differences in implantation technique, device design, and operator experience.Surgical LAA Exclusion and ExcisionMadden23 suggested >60 years ago that resection of the LAA could prevent recurrent arterial emboli caused by AF. Surgical exclusion or removal of the LAA during cardiac surgery in AF patients is now commonplace and forms in part the rationale for the development of transcatheter approaches to LAA closure. However, surgical LAA closure frequently appears to be incomplete, and residual flow may be associated with thromboembolic events. In the pilot Left Atrial Appendage Occlusion Study (LAOOS), 34% of patients had residual flow into the LAA after surgical exclusion.24 Imaging studies of patients after surgical exclusion or excision have also documented relatively high rates of incomplete closure, although it is least frequent with LAA excision.25–28 The findings of observational studies that have examined the association between surgical LAA closure and stroke reduction are conflicting.28,29 A large, randomized trial examining the clinical efficacy of surgical LAA closure for stroke prevention is currently ongoing.30Devices to improve anatomic closure of the LAA during surgery have been developed. The AtriClip (Atricure, West Chester, OH) consists of 2 parallel titanium tubes and 2 nitinol springs with a knit-braided polyester fabric31 delivered with a deployment tool consisting of a distal articulating head connected to a shaft and proximal actuator. The US Food and Drug Administration (FDA) approval states that it is indicated for LAA occlusion under direct visualization in conjunction with other open cardiac surgical procedures. The Exclusion of Left Atrial Appendage With AtriClip Exclusion Device in Patients Undergoing Concomitant Cardiac Surgery (EXCLUDE) study was a prospective observational study that examined device safety and anatomic closure in 71 patients undergoing concomitant cardiac surgery via a median sternotomy.32 There were no device-related adverse events, and LAA closure was achieved in 95% of patients who completed 3-month imaging follow-up. However, efficacy data for stroke prevention in the absence of oral anticoagulation are lacking. Successful standalone thoracoscopic implantation of the AtriClip has been reported.33 The safety and anatomic efficacy of such a minimally invasive approach in AF patients with contraindications to anticoagulation are being evaluated in the observational Stroke Feasibility Study (http://www.clinicaltrials.gov; NCT01997905).Transcatheter Closure StrategiesPLAATOThe PLAATO system was the first transcatheter device developed for the purpose of LAA closure.34 The device consisted of a self-expanding nitinol cage covered with an expanded polytetrafluoroethylene membrane. Device feasibility was evaluated in a nonrandomized, multicenter study of 64 patients who were at high thromboembolic risk but were not candidates for warfarin.35 There was a high rate of anatomic closure at the time of the procedure (residual flow ≤3 mm in 98%), and safety was excellent. At the 5-year follow-up, the observed rate of stroke or transient ischemic attack was 3.8%/y compared with an expected rate of 6.6% based on the CHADS2 score of the study population. Although this device was not evaluated further, the PLAATO experience serves as a proof of principle for device occlusion of the LAA for stroke prevention.WATCHMANDevice CharacteristicsThe WATCHMAN (Boston Scientific, Natwick, MA) consists of a self-expanding nitinol frame and membrane cap (Figure 1). The device is delivered through a 14F sheath placed within the LAA, guided by a combination of fluoroscopy and transesophageal echocardiography (TEE; Figure 2).Download figureDownload PowerPointFigure 1. WATCHMAN device. The WATCHMAN device is made of a self-expanding nitinol frame with a polyethylene terephthalate fabric cap. Distal tines secure the device within the left atrial appendage (LAA) trabeculae. The device is fully retrievable before release from the delivery cable. Device length is approximately equal to its diameter. Device size is selected on the basis of the largest diameter of the LAA ostium, which is measured by drawing a line from the mitral valve annulus across to the ridge of left upper pulmonary vein, perpendicular to the planned axis of the delivery sheath. Alternatively, the LAA ostium can be measured from the mitral valve annulus to a point ≈2 cm distal from the tip of the left upper pulmonary vein ridge.Download figureDownload PowerPointFigure 2. WATCHMAN implantation. A, Left atrial appendage (LAA) angiography through a diagnostic pigtail catheter introduced through the delivery sheath within the left atrium. B, Delivery sheath is advanced deeply within the LAA over the pigtail catheter to avoid traumatizing the thin-walled appendage. C, The WATCHMAN is deployed, and angiography demonstrates appropriate position and seal. Contrast material penetrates through the WATCHMAN because the membrane cap is a 160-μm filter. D, Final fluoroscopy after release.Clinical DataThe safety and clinical efficacy of the WATCHMAN have been examined in 2 randomized, clinical trials; a nonrandomized, continuing-access registry was performed for the purpose of evaluating device and procedural safety (Table 3). The WATCHMAN Left Atrial Appendage System for Embolic Protection in Patients With Atrial Fibrillation (PROTECT-AF) and Prospective Randomized Evaluation of the Watchman Left Atrial Appendage Closure Device in Patients With Atrial Fibrillation Versus Long Term Warfarin Therapy (PREVAIL) studies, which enrolled 707 and 407 patients, respectively, were noninferiority trials that evaluated the WATCHMAN compared with warfarin in AF patients who were candidates for long-term anticoagulation.36,39 PROTECT-AF required enrolled subjects to have a CHADS2 score ≥1, whereas PREVAIL required a CHADS2 score ≥2 or 1 if additional stroke risk factors were present and warfarin therapy was recommended according to society guidelines. In PREVAIL, a minimum of 20% of patients were required to be enrolled at sites without prior WATCHMAN experience. Otherwise, the enrollment criteria for the 2 trials were similar. Patients were randomly assigned to either device implantation or warfarin therapy in a 2:1 fashion. Patients allocated to device implantation were treated with 6 weeks of warfarin and aspirin, at which time a follow-up TEE was performed. If the TEE findings were adequate (ie, no thrombus and peri-device leak<5 mm), warfarin was discontinued, and aspirin and clopidogrel were prescribed for 5 more months, followed by aspirin indefinitely. Both trials used bayesian statistics, which is an approach to combining prior information with current information as it accumulates.Table 3. Efficacy Outcomes in the Randomized, Clinical Trials of the WATCHMAN Compared With Warfarin in Patients With Nonvalvular AFnPopulation StudiedControlPrimary End PointNI Margin (Upper Bound of 95% CrI)Duration of Follow-UpTreatment Effect (95% CrI)NI Achieved?PROTECT-AF36–38707Warfarin eligible, CHADS2 score ≥1WarfarinCVD, any stroke, or SERR <2.01065 patient-yRR, 0.62 (0.35 to 1.25)Yes1588 patient-yRR, 0.71 (0.44 to 1.30]Yes2621 patient-yRR, 0.60 (0.41 to 1.05)YesPREVAIL39407Warfarin eligible, CHADS2 score ≥2 or 1 plus an additional RFWarfarin1. CVD, any stroke, or SERR <1.7511.8±5.8 moRR, 1.07 (0.57 to 1.89)No2. Any stroke or SE >7 d after the procedureRate difference <0.0275Difference, 0.0053 (−0.0190 to 0.0273)YesAF indicates atrial fibrillation; CrI, credible interval; CVD, cardiovascular death; NI, noninferiority; RR, rate ratio; and SE, systemic embolism.EfficacyIn the PROTECT-AF trial, the WATCHMAN was noninferior to warfarin for the primary end point of cardiovascular/unexplained death, any stroke, or systemic embolism at 1065,36 1588,37 and at 2621 patient-years of follow-up38 (Table 1). At 2621 patient-years, the WATCHMAN met the criterion for superiority. All-cause mortality was significantly reduced with the WATCHMAN at this late follow-up (hazard ratio, 0.66; 95% confidence interval, 0.45–0.98; frequentist P=0.038). There was a significant improvement in quality-of-life measures in patients assigned to the WATCHMAN compared with those assigned to warfarin therapy.40 Limitations of these analyses include a greater rate of voluntary withdrawal in the warfarin arm; a higher rate of hemorrhagic stroke in the warfarin-treated patients compared with prior experiences; inclusion of patients with CHADS2 score of 1, who may not require anticoagulation; and a relatively large noninferiority margin, although the observed upper bound of the 95% credible interval during follow-up was substantially below this margin.In the smaller PREVAIL trial, the 18-month rates of the coprimary end point of cardiovascular death, any stroke, or systemic embolism were numerically similar between WATCHMAN and warfarin, but the device did not achieve noninferiority because the upper bound of the 95% credible interval for the 18-month rate ratio was not lower than the prespecified noninferiority margin of 1.75 (Table 1). This finding should be interpreted in the context of a lower-than-expected event rate, particularly among the patients assigned to warfarin, and the relatively short duration of follow-up.Further analyses support the mechanistic hypothesis that LAA occlusion reduces thromboembolic risk in the absence of oral anticoagulation. Landmark analyses of PROTECT-AF confined to the periods after the procedure and after termination of warfarin and clopidogrel therapy in the device arm demonstrated that the primary end point and ischemic stroke rates were similar in the patients receiving the WATCHMAN compared with those treated with warfarin.37,38 In PREVAIL, WATCHMAN implantation was noninferior to warfarin for the coprimary end point of ischemic stroke or systolic embolism occurring >7 days after randomization (Table 1).SafetyIn PROTECT-AF, the rate of the major safety end point (excessive bleeding or a procedure-related complication) at 18 months was greater in the patients assigned to the WATCHMAN compared with warfarin (rate ratio, 1.69; 95% credible interval, 1.01–3.19), driven by pericardial effusions and procedure-related ischemic stroke.36,41 Most safety events in the device arm occurred within the first 7 days after the procedure.41 These observations led in part to the conduct of the PREVAIL trial to determine whether the procedural modifications instituted during PROTECT-AF, combined with enhanced operator training, would lead to an improved safety profile. However, ongoing follow-up provides insight into the temporal risks and benefits of LAA closure with the WATCHMAN: Over the longer term, the difference in the cumulative rate of safety events narrowed between treatment groups as a result of bleeding events in the warfarin arm so that, at 2621 patient-years of follow-up, there was no significant safety difference between the WATCHMAN and warfarin (rate ratio, 1.17; 95% credible interval, 0.78–1.96).38In PREVAIL, new operators without prior WATCHMAN experience enrolled 39% of the patients. Despite the technical inexperience of these investigators, the WATCHMAN met the safety performance goal prespecified by the sponsor and the FDA. Safety events related to the procedure, including the incidence of serious pericardial effusions and procedural stroke, were significantly reduced compared with PROTECT-AF (Table 4). Implantation by new operators was not associated with reduced rates of implantation success or an increased risk of major adverse events. This improved safety profile was consistent with the findings of the continuing-access registry that followed the PROTECT-AF trial.41Table 4. Safety Outcomes in the Randomized Trials and Continued-Access Registry of the WATCHMAN Device Compared With WarfarinOutcomeStudyP ValuePROTECT-AF(n=463), %CAP(n=566), %PREVAIL(n=269), %Any complication within 7 d of procedure8.74.14.70.04Procedure-related stroke1.100.70.02Pericardial effusion requiring surgery1.61.20.70.03Pericardial effusion requiring pericardiocentesis2.41.21.50.32Device embolization0.40.20.70.37CAP indicates Continued Access to Protocol; PREVAIL, Watchman Left Atrial Appendage Closure Device In Patients With Atrial Fibrillation Versus Long Term Warfarin Therapy; and PROTECT-AF, Watchman Left Atrial Appendage System for Embolic Protection in Patients With AF. Adapted from Holmes et al.39 Authorization for this adaptation has been obtained both from the owner of the copyright in the original work and from the owner of copyright in the translation or adaptation.Anatomic ClosurePeri-device flow into the LAA is not uncommon after WATCHMAN implantation. In PROTECT-AF, flow around the device was detected by TEE in 41% and 32% of patients at 6 weeks and 1 year after the procedure, respectively.22 In a post hoc analysis, there was no association between clinical events and the presence of peri-device flow, regardless of size and whether warfarin was continued.22 This analysis has limited power because of a small number of events. Whether residual leaks are clinically important with other devices is unknown and may depend on the mechanism of closure.Other DataStroke prevention strategies are particularly challenging in patients in whom anticoagulation is contraindicated. ASA Plavix Feasibility Study With Watchman Left Atrial Appendage Closure Technology (ASAP) was a prospective, multicenter, observational study that examined clinical outcomes with the WATCHMAN device in 150 AF patients who were ineligible for warfarin,42 predominantly because of prior bleeding. Patients were treated with clopidogrel for 6 months and aspirin indefinitely after implantation. At a mean follow-up of 14.4±8.6 months, the observed rate of stroke or systemic embolism was 2.3%/y, significantly less than the expected rate of 7.3%/y based on CHADS2 score. Important limitations of this study include its nonrandomized design, the small number of patients enrolled, and the use of an expected stroke rate as the comparator. In addition, dual antiplatelet therapy with aspirin and clopidogrel is associated with a bleeding hazard similar to that of warfarin in anticoagulant-eligible patients.43 Therefore, the relative safety of this medical regimen in patients at very high bleeding risk is not known. A larger data set is required to adequately define the role and appropriate postprocedural medical regimen of LAA occlusion with the WATCHMAN in patients who cannot tolerate OACs as a result of prior bleeding or other contraindications.Amplatzer Cardiac PlugDevice CharacteristicsThe Amplatzer Cardiac Plug (St. Jude Medical, Minneapolis, MN) has CE mark and is not approved for use in the United States at this time. It is a self-expanding nitinol mesh that consists of a distal lobe and proximal disk, each with a sewn polyester patch, connected by a short central waist (Figure 3).44,45 The proximal disk covers the mouth of the LAA from within the left atrium; therefore, the mechanism of LAA occlusion differs from that of the WATCHMAN, which occludes the LAA from within the appendage itself. The device is delivered from the femoral vein via a transseptal puncture using a combination of fluoroscopic and TEE guidance.Download figureDownload PowerPointFigure 3. Amplatzer Cardiac Plug. The Amplatzer Cardiac Plug is a self-expanding nitinol device consisting of a distal lobe and proximal disk with sewn-in polyester fabric connected by a central waist. The distal lobe has hooks around its circumference and anchors the device within the appendage, while the disk is positioned proximally along the plane of the tip of the left upper pulmonary venous ridge and the mitral valve annulus, thereby occluding the mouth of the left atrial appendage (LAA). Device size is selected on the basis of the maximal diameter of the distal lobe landing zone, measured ≈10 mm distal to the LAA orifice. A second-generation device has a slightly longer distal lobe, more stabilizing hooks, a longer central waist, and a larger-diameter proximal disk to facilitate implantation and to improve LAA sealing.45Clinical Safety and EfficacyClinical data with the Amplatzer Cardiac Plug are derived from several small, observational studies, many of which are retrospective in design or involve a single center or operator (Table 5).44,46–52 Most of the patients enrolled in these studies had intolerance of or contraindications to OAC and were treated with aspirin and clopidogrel during the postprocedural period. The most frequent safety events appear to be pericardial effusions and device embolization, occurring at rates similar to those of the WATCHMAN experience. Although these observational findings are encouraging, a large, monitored, preferably randomized trial is necessary to robustly assess safety and efficacy because the mechanisms of implantation and closure differ from those of the WATCHMAN. A large, randomized, clinical trial of the Amplatzer Cardiac Plug compared with OAC (http://www.clinicaltrials.gov; NCT01118299) was recently halted, likely because of the anticipated FDA approval of the WATCHMAN, which would make it difficult to enroll patients in such a trial.Lariat ProcedureDevice CharacteristicsThe Lariat device (SentreHeart, Redwood City, CA) enables the transcatheter ligation of the LAA through the delivery of a surgical suture via a combined transseptal and subxiphoid approach53,54 (Figure 4). The device is 510K-cleared by the FDA for the approximation of soft tissue, although it has been applied clinically to LAA ligation. Preprocedural cardiac computed tomography imaging is mandatory to assess anatomic eligibility: Appendages with diameter >40 mm, that have lobes behind the pulmonary artery, or that are posteriorly oriented should be avoided. A micropuncture or 17-gauge epidural needle is used to advance a guide wire and then a 14F sheath into the pericardial space. Therefore, unique to the Lariat, procedural complications can arise related to dry pericardial access. Transseptal puncture is then performed via the femoral vein. A magnet-tipped guide wire is advanced into the anterior aspect of the LAA, and a complementary magnet-tipped guide wire is advanced into the pericardium through the pericardial sheath to form a connection with the magnet-tipped wire in the LAA, over which the Lariat snare is advanced and closed at the LAA ostium with the use of TEE and fluoroscopic guidance. This snare contains a preloaded surgical knot, which is released with a proximal actuator and then tightened with a suture-tensioning device, after which the snare is removed and the suture is cut with a suture cutter. The pericardial sheath is exchanged for a drain, which is generally left in place for at least 4 to 6 hours.Download figureDownload PowerPointFigure 4. Transcatheter left atrial appendage (LAA) ligation with the Lariat. A, A magnet-tipped wire has been advanced through a transseptal sheath into the anterior lobe of the LAA and connected to a complementary magnet-tipped wire that has been advanced through a pericardial sheath, forming a rail over which the Lariat snare has been opened and advanced to the base of the LAA. B, The Lariat is closed, and the appropriate position and occlusion are confirmed by angiography and transesophageal echocardiography. The endocardial (inner) wire and catheter are then removed, and an actuator deploys a pretied surgical suture from within the Lariat snare and ligates the LAA.Clinical Safety and EfficacyTo date, the safety and efficacy of LAA closure with the Lariat have been limited to a very few small, observational studies.55,56 In the largest reported prospective experience, Bartus et al55 conducted a single-center, nonrandomized study that enrolled 92 patients who were poor candidates or ineligible for warfarin therapy. The procedure was aborted in 3 patients (3.2%) because of unexpected pericardial adhesions. Successful closure (residual leak<1 mm) was achieved in 96% of cases. Procedural complications, all of which were significant pericardial effusions, occurred in 3 patients, and pericarditis occurred in 2 patients. At the 1-year follow-up, 55% of the patients remained on warfarin therapy, and there were no thromboembolic events. A multicenter, retrospective study examined the early safety and efficacy of LAA closure with the Lariat device in 154 patients undergoing the procedure in the United States.57 Device success (suture deployment and <5-mm leak by postprocedural TEE) was 94%. Procedure-related major bleeding occurred in 9.1% and a significant pericardial effusion occurred in 10.4% of patients. Thrombus at the site of Lariat ligation has also been reported,58,58a but the actual rate of thrombus is unknown. Late leaks have been observed, but the clinical implications of such leaks are unclear.59In summary, from the small amount of data available, the Lariat appears to provide high rates of acute anatomic closure, although procedural morbidity, driven by bleeding events, pericardial effusions, and pericarditis, is not uncommon. Clinical efficacy data are absent. Several other questions about the Lariat remain unanswered, including whether safety events can be reduced with increased operator experience and what postprocedural medical therapy is required (ie, a brief duration of antiplatelet or anticoagulation therapy).Other DevicesSeveral other LAA closure devices are currently in development. The WaveCrest LAA occluder (Coherex Medical, Salt Lake City, UT) is unique in that device implantation is a 1-step process. First, the proximal expanded polytetrafluoroethylene cap/occluder is positioned, and then the distal anchors are deployed. Incorporation of foam into the edges of the occluder could potentially enhance LAA sealing. This device currently has a CE mark, and initiation of a pivotal trial within the United States is planned. The LAmbre LAA occluder (Lifetech Scientific Corp, Shenzhen, China)60 is a self-expanding nitinol device consisting of a distal, hook-embedded umbrella and a proximal covering disk, both with sewn-in polyethylene terephthalate fabric. A short, articulating central waist connects the umbrella and cover.Unresolved QuestionsReservoir and Hormonal Functions of the LAAThe LAA is more compliant than the main left atrial chamber and appears to play an important role in left atrial pressure and volume overload.61 In theory, LAA closure may negatively affect left atrial function and induce left atrial diastolic dysfunction by eliminating this reservoir function. In addition, LAA resection may reduce circulating atrial natriuretic peptide levels, resulting in fluid retention.62 The effects on left atrial reservoir and hormonal function may differ among occlusion techniques (eg, filter occlusion versus acute ligation and necrosis of the LAA tissue). Studies of LAA closure to date have not specifically addressed these issues.Operator QualificationsThere has been much debate whether interventional cardiologists or electrophysiologists should be performing transcatheter LAA closure. The relevant factor is proficiency in performing the necessary procedural steps. Keys to successful transcatheter LAA closure include competency performing transseptal puncture, understanding of the 3-dimensional anatomy of the left atrium and LAA and their echocardiographic and fluoroscopic correlates, specific training for each device, and competency in managing complications specific to LAA closure, including pericardiocentesis and retrieval of embolized devices" @default.
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• W2149778877 title "Left Atrial Appendage Closure to Prevent Stroke in Patients With Atrial Fibrillation" @default.
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• W2149778877 doi "https://doi.org/10.1161/circulationaha.114.009060" @default.
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