Left Atrial Appendage Occlusion Study Research Articles

Incidence and predictors of heart failure events following cardiac surgery in patients with atrial fibrillation - insights from the LAAOS-III trial

Abstract Background Atrial fibrillation (AF) is a common comorbidity in patients undergoing cardiac surgery and further increases the risk of incident heart failure (HF). However, only limited data exist on HF events following surgery in patients with AF. Methods The Left Atrial Appendage Occlusion Study (LAAOS) III was a randomized trial evaluating concomitant left atrial appendage occlusion in patients with AF undergoing cardiac surgery. In this secondary analysis, we aimed to identify independent predictors of the composite outcome of HF hospitalization or HF-related death following discharge, using a multivariable Cox model – incorporating sex, age (≥65 vs <65 years), systolic blood pressure (≤140 vs >140 mmHg), body mass index (BMI; <25 vs 25-29.9 vs ≥30 kg/m2), diabetes mellitus (DM), prior HF diagnosis, prior stroke, ischemic heart disease (IHD), heart valve surgery, AF history duration, rhythm on discharge electrocardiogram, and trial allocation. Supplementary analyses were undertaken to further assess the continuous variables using cubic spline regression. Results Of 4770 patients enrolled, in-hospital death occurred in 201 (4.2%) and complete discharge data were available for 4564 (95.7%). During a median follow up of 3.9 years, 533 (11.7%) of 4564 patients were hospitalized for HF. In total, 873 (19.1%) died after discharge, including 95 HF-related deaths. The composite outcome of HF hospitalization or HF-related death occurred at an annualized event rate of 3.31%/year [95% confidence interval: 3.04-3.60]. The independent risk factors included age (event rate of 3.64%/year vs 2.03%/year for ≥65 vs <65 years; hazard ratio (HR) 1.71 [1.32-2.21]), DM (4.71%/year vs 2.71%/year for with vs without DM; HR 1.59 [1.34-1.90]), prior HF diagnosis (4.27%/year vs 2.17%/year for with vs without HF; HR 2.00 [1.66-2.41]), IHD (3.63%/year vs 2.85%/year for with vs without IHD; HR 1.26 [1.03-1.54]), AF history duration (3.81%/year vs 2.89%/year for >2 vs <0.5 years; HR 1.23 [1.01-1.50]), and AF rhythm at discharge (3.87%/year vs 2.68%/year for AF vs non-AF rhythm; HR 1.31 [1.09-1.58]). The supplementary spline analyses further revealed a positive correlation between BMI and the risk of the composite outcome (p-value 0.042). Conclusions In patients with AF undergoing cardiac surgery, post-discharge HF hospitalization and HF-related death occurred at a rate of 3.31% per year. Our study identified several significant risk factors including advanced age, higher BMI, DM, prior HF diagnosis, IHD, AF history >2 years, and AF rhythm at discharge.The associations of HF with age and BMI

Heart failure after left atrial appendage occlusion: insights from the LAAOS-III randomized trial

Abstract Background Left atrial appendage removal or occlusion (LAAO) might increase the risk for heart failure (HF) due to the loss of the LAA`s reservoir function, active contraction and neuroendocrine function. Purpose To investigate the incidence of HF hospitalizations and/or HF related death after LAAO in the Left Atrial Appendage Occlusion Study (LAAOS III). Methods In LAAOS III, 4811 patients with atrial fibrillation (AF) and a CHA2DS2-VASc score ≥2 were randomized to undergo or not undergo surgical LAAO during cardiac surgery for another indication. We compared the incidence of a composite endpoint of HF hospitalizations and HF related death between the two randomized groups (LAAO vs no-LAAO). We also pre-specified subgroups including: sex, age, BMI, surgery type, concomitant AF ablation, prior history of HF, history of hypertension, diabetes, prior myocardial infarction, left ventricular ejection fraction, sinus rhythm and occlusion method. Results We included 2379 patients in the LAAO and 2391 patients in the no-LAAO group. Overall, mean age was 71 years, 67% were male and 57% had prior HF. Baseline characteristics including drug treatment were balanced between the groups. Over a mean follow-up of 3.8 years, 395 (8.3%) patients met the primary HF endpoint: 209 (8.8%) in the LAAO group and 186 (7.8%) in the no-LAAO group. We did not find a significant difference for the primary endpoint between the randomized groups (Hazard ratio [95% confidence intervals] 1.13 [0.93-1.37], p=0.233) (Figure). The only significant subgroup interaction was for concomitant AF ablation (p for interaction = 0.004). Patients in the LAAO group without concomitant AF ablation had a higher risk for the primary endpoint (HR [95% CI] 1.37 [1.08-1.74], p=0.009) than patients with ablation (HR [95% CI] 0.74 [0.51-1.06], p=0.097). Conclusion LAAO did not increase the risk for a combined endpoint of HF hospitalizations and HF related death in patients with AF. Patients with concomitant AF ablation might have lower risk for the combined endpoint.Figure

Oral Anticoagulation Use and Left Atrial Appendage Occlusion in LAAOS III.

LAAOS III (Left Atrial Appendage Occlusion Study III) showed that left atrial appendage (LAA) occlusion reduces the risk of ischemic stroke or systemic embolism in patients with atrial fibrillation undergoing cardiac surgery. This article examines the effect of LAA occlusion on stroke reduction according to variation in the use of oral anticoagulants (OACs). Information regarding OAC use was collected at every follow-up visit. Adjusted proportional hazards modeling, including using landmarks of hospital discharge, 1 and 2 years after randomization, evaluated the effect of LAA occlusion on the risk of ischemic stroke or systemic embolism, according to OAC use. Adjusted proportional hazard modeling, with OAC use as a time-dependent covariate, was also performed to assess the effect of LAA occlusion, according to OAC use throughout the study. At hospital discharge, 3027 patients (63.5%) were receiving a vitamin K antagonist, and 879 (18.5%) were receiving a non-vitamin K antagonist oral anticoagulant (direct OAC), with no difference in OAC use between treatment arms. There were 2887 (60.5%) patients who received OACs at all follow-up visits, 1401 (29.4%) who received OAC at some visits, and 472 (9.9%) who never received OACs. The effect of LAA occlusion on the risk of ischemic stroke or systemic embolism was consistent after discharge across all 3 groups: hazard ratios of 0.70 (95% CI, 0.51-0.96), 0.63 (95% CI, 0.43-0.94), and 0.76 (95% CI, 0.32-1.79), respectively. An adjusted proportional hazards model with OAC use as a time-dependent covariate showed that the reduction in stroke or systemic embolism with LAA occlusion was similar whether patients were receiving OACs or not. The benefit of LAA occlusion was consistent whether patients were receiving OACs or not. LAA occlusion provides thromboembolism reduction in patients independent of OAC use.

Cost Implications of Left Atrial Appendage Occlusion During Cardiac Surgery: A Cost Analysis of the LAAOS III Trial.

Background The LAAOS III (Left Atrial Appendage Occlusion Study) clinical trial demonstrated that concomitant left atrial appendage (LAA) occlusion leads to a lower risk of ischemic stroke or systemic embolism compared with no occlusion in participants with atrial fibrillation and a CHA2DS2-VASc score of ≥2 undergoing cardiac surgery for another indication. We report the cost implications of concomitant LAA occlusion during cardiac surgery. Methods and Results Using LAAOS III data, we compared the costs (in US dollars) associated with LAA occlusion to no occlusion from the perspective of the Centers for Medicare and Medicaid Services. We calculated the average cost per participant during the trial by applying Medicare reimbursement costs to cardiovascular events for all trial participants. We conducted sensitivity analyses, varying the cost of stroke ±25% and occlusion technique use. Cost neutrality was defined as a mean cost difference within ±5% of the cost per participant in the no-occlusion group. Total study cost per participant was $3878 in the LAA occlusion group and $4490 in the no-occlusion group, a mean difference of -$612 (95% CI, -$1276 to $45). The main drivers of cost savings were fewer stroke events during the trial (mean difference of -$1021). In sensitivity analyses, LAA occlusion was cost saving for suture and stapler techniques but more expensive with closure device. Conclusions Concomitant LAA occlusion was cost saving for participants in LAAOS III. Our findings support concomitant LAA occlusion as an economically dominant strategy for patients with atrial fibrillation and a CHA2DS2-VASc score of ≥2 undergoing cardiac surgery.

Surgical atrial appendage closure: time for a randomized study

Atrial fibrillation (AF) is the most common arrhythmia and is assumed to affect more than 30million people worldwide. Studies report that the left atrial appendage (LAA) plays an important role in thrombus formation and is considered the embolic source in90% of affected patients with non-valvular and57% with valvular AF. Oral anticoagulants have been the standard of care for stroke prevention in patients with AF for decades. However, bleeding complications and noncompliance are barriers to effective embolic protection. Therefore, as an alternative to conventional anti-thrombotic therapy, surgical LAA occlusion, which may lead to areduced risk of thromboembolism, has received increasing attention. However, the procedure can be associated with additional risks such as prolonged operation time, damage to the circumflex coronary artery, and incomplete LAA occlusion. This review discusses some of the observational studies that have examined the impact of LAA occlusion on stroke, the LAAOSIII (Left Atrial Appendage Occlusion Study) trial, which provided definitive evidence for the benefit of surgical LAA occlusion on ischemic stroke, which surgical methods are safe and effective for LAA occlusion, and whether oral anticoagulation can be stopped after surgical removal of the LAA.

Concomitant Surgical Left Atrial Appendage Occlusion: a Review.

In this review, we discuss some of the observational studies that examined the impact of left atrial appendage occlusion on stroke, the Left Atrial Appendage Occlusion Study (LAAOS) III research program that provided definitive evidence for the benefit of surgical left atrial appendage occlusion on ischemic stroke, and high priority studies in the field that should be pursued by the surgical community. Atrial fibrillation is common in patients undergoing cardiac surgery. Oral anticoagulants are effective at preventing strokes related to atrial fibrillation; they have been the standard of care for stroke prevention in patients with atrial fibrillation for decades. Most strokes in patients with atrial fibrillation originate from the left atrial appendage. LAAOS III, a large randomized controlled trial, has recently demonstrated that concomitant left atrial appendage occlusion in patients undergoing cardiac surgery for another indication reduces the risk of stroke or systemic embolism on top of oral anticoagulation. Surgical left atrial appendage occlusion reduces the risk of ischemic stroke and systemic embolism in patients with atrial fibrillation and a CHA2DS2-VASc score ≥ 2 undergoing cardiac surgery for another indication. The role of surgical left atrial appendage occlusion with patients without atrial fibrillation, as a substitute to anticoagulation and as a standalone procedure, remains unclear.

Alas, the Return of the Lasso

Independent of the imperative to surgically treat concomitant atrial fibrillation, surgeons should close the left atrial appendage (LAA). The Left Atrial Appendage Occlusion Study (LAAOS III)1 is the third installment of the arduous march to establish the effect of LAA closure during cardiac surgery in atrial fibrillation patients. For many, leaving a patent LAA in an atrial fibrillation patient is to turn our backs on clear evidence revealing that the LAA is a persistent danger. We know that standard of care does not translate into lifelong anticoagulation compliance.

Concomitant left atrial appendage occlusion in patients undergoing cardiac surgery.

The Left Atrial Appendage Occlusion Study (LAAOS III) was a multicenter, randomized controlled trial that included patients undergoing cardiac surgery who also had atrial fibrillation. The trial recruited 4811 participants, of which 2400 patients were randomized to undergo left atrial appendage (LAA) occlusion surgery, while 2411 participants had isolated cardiac surgery. The aim of the study was to determine whether concomitant occlusion of the LAA prevents ischemic stroke or systemic embolism. The study also evaluated the efficacy and safety of concomitant LAA occlusion in patients undergoing cardiac surgery. The number of ischemic strokes or systemic embolisms was significantly lower in the LAA occlusion group [114 (4.8%) vs. 68 (7.0%)] compared to the no-occlusion surgery group. There was also no increase in hospital length of stay or hospitalization for heart failure. It is expected that based on the findings of the LAAOS III study, the recommendations for concomitant LAA occlusion will be upgraded from the current class IIB to class I.

Patients with Atrial Fibrillation Undergoing Cardiac Surgery: No Left Atrial Appendage Shall Remain Untouched

The Left Atrial Appendage Occlusion Study III randomized 4,811 patients with atrial fibrillation and a CHA2DS2VASc score ≥2 undergoing cardiac surgery to surgical left atrial appendage occlusion or no occlusion. At a mean follow-up of 3.8 years, stroke or systemic embolism was reduced by 33% in the occlusion group with no evidence of early or late adverse effects. This review discusses the implication of these findings.

Vitamin K antagonists versus direct oral anticoagulants after cardiac surgery: a 31-country cohort study

Abstract Background About 10% of patients undergoing cardiac surgery have a history of atrial fibrillation (AF). Among these patients, uncertainty exists regarding the safest and most effective oral anticoagulant (OAC) during the postoperative period. Purpose To evaluate practice patterns regarding OAC early after cardiac surgery in patients with a preoperative history of AF and to compare the safety and effectiveness of direct oral anticoagulants (DOACs) versus vitamin K antagonists (VKAs). Methods We conducted a nested cohort study within the Left Atrial Appendage Occlusion Study (LAAOS) III (NCT01561651). LAAOS III included patients with AF undergoing cardiac surgery with a CHA2DS2-VASC ≥2. In this substudy, we examined patients without end-stage renal dysfunction (eGFR >30 mL/min/1.73m2) who were discharged on OAC. We evaluated bleeding and thromboembolism within 90 days postoperatively using logistic regression adjusting for CHA2DS2-VASC score. Results Recruitment started in 2012 and completed in 2018 in 113 centres in 31 countries. Of the 4811 patients enrolled in LAAOS III, 3725 (77%) were included in this substudy. Preoperatively, 58% of patients received OAC: 56% DOACs and 44% VKAs. At hospital discharge 23% received DOACs and 77% VKAs; 55% of patients on a DOAC at baseline were switched to a VKA while 5% of patients on a VKA were switched to a DOAC. Patients discharged on a DOAC were older, had a higher CHA2DS2-VASC, and were more likely to be male. Patients having undergone an isolated coronary bypass procedure were more likely prescribed DOACs than VKAs (41% vs 23%, p<0.001) whereas isolated non-mechanical valve patients were more likely to be prescribed VKAs (43% vs 28%, p<0.001). Switching from a DOAC to a VKA postoperatively occurred in 42% of patients In Australia/New Zealand, 49% in Europe, and 63% in North America. Major bleeding between 48 hours postoperatively and 30 days occurred in 1.5% in the DOAC group and 1.3% in the VKA group (aOR 1.14, 95% CI 0.60–2.15, p=0.69) while between 48 hours and 90 days, it occurred in 1.8% of patients in both groups (aOR 0.97, 95% CI, 0.54–1.17, p=0.91). Cardiac tamponade, the composite of stroke and systemic arterial embolism, and the composite of stroke, systemic arterial embolism and death did not differ significantly at 30 and 90 days between the DOAC and VKA groups. Conclusions VKAs was the dominant OAC used early after cardiac surgery, but postoperative OAC practices varied by region. After adjustment for CHA2DS2-VASC score, the early postoperative incidence of major bleeding and of the composite of stroke and systemic arterial embolism did not differ significantly when DOACs were compared with VKAs. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): CIHR, Heart and Stroke Foundation

Costs of surgical ablation of atrial fibrillation in Ontario, Canada from 2006 to 2017.

International guidelines currently recommend concomitant surgical ablation of atrial fibrillation (AF) in patients with AF undergoing cardiac surgery. However, a systematic review and meta-analysis of 23 randomized controlled trials (RCTs) showed no significant difference in mortality or stroke in patients who underwent surgical AF ablation compared with those who did not (moderate-quality evidence). We estimated the Ontario-wide costs of surgical AF ablation between 2006 and 2017 using data from a systematic review and meta-analysis of RCTs, estimates of case volumes from Ontario Health Insurance Plan fee codes, the ongoing left atrial appendage occlusion study III trial (NCT01561651), institutional costs from large academic centers in Ontario, as well as professional fees based on the Ontario fee schedule. Device costs were obtained from Canadian industry data with expert input. We estimated the average extra cost of surgical AF ablation at $4,287 CAD (95% CI $4,113-4,619) per patient. Procedural costs (equipment costs and physician remuneration) comprise 82.2% of this, while smaller portions relate to the increased need for pacemaker (3.9%) and additional hospital length of stay (13.9%). Approximately 2,391 patients underwent surgical AF ablation between 2006 and 2017, corresponding to an estimated $10.2 million in incremental cost during that time span. Ontario taxpayers spend significant financial resources on surgical ablation of AF, a procedure lacking high-quality evidence demonstrating benefit in reducing mortality or stroke. Further large prospective studies examining clinically important outcomes are needed to justify its routine use in patient care and to guide allocation of healthcare funds.

Surgical Closure of the Left Atrial Appendage: The Past, The Present, The Future.

Occlusion of the left atrial appendage (LAA) may protect against stroke in patients with atrial fibrillation. While percutaneous LAA closure devices have demonstrated efficacy in stroke reduction, surgical LAA occlusion has been performed with mixed results to date. Although surgical exclusion via internal sutures or noncutting stapler is ineffective due to recanalization of the LAA, surgical excision and certain exclusion devices including the AtriClip device are effective methods to achieve complete closure of the LAA. No data currently exists to support routine, prophylactic LAA closure at the time of cardiac surgery, but this practice may benefit certain patients at high risk for stroke. The currently enrolling Left Atrial Appendage Occlusion Study (LAAOS) III is the largest study to date designed to assess the efficacy of LAA occlusion for stroke prevention. The results of this trial will inform future clinical practice regarding stroke prevention with surgical LAA occlusion for patients with atrial fibrillation. Meanwhile, the ATLAS trial is investigating the efficacy of LAA occlusion in surgical patients who do not have atrial fibrillation but are at increased risk for developing it post-operatively.

Totally Endoscopic Robotic Left Atrial Appendage Closure Demonstrates High Success Rate.

In patients with atrial fibrillation, 90% of embolic strokes originate from the left atrial appendage (LAA). Successful exclusion of the LAA is associated with a lower stroke rate in patients with atrial fibrillation. Surgical oversewing of the LAA is often incomplete when evaluated with transesophageal echocardiogram (TEE). External closure techniques of suturing and stapling have also demonstrated high failure rates with persistent flow and large stumps. We hypothesized that the precise visualization of a robotic LAA closure (RLAAC) would result in superior closure rates. Before robotic mitral repair, patients underwent RLAAC; the base of the LAA was oversewn using a running 4-0 polytetrafluoroethylene suture in two layers. Postoperatively, the LAA was interrogated in multiple TEE views. Incomplete closure was defined as any flow across the LAA suture line or a residual stump of greater than 1 cm. Seventy-nine consecutive patients underwent RLAAC; no injuries occurred. On postrepair TEE, 73 of 79 patients had LAAs visualized well enough to thoroughly evaluate. Successful ligation was confirmed in 64 (87.7%) of 73 patients. Seven patients (9.6%) had small jet flow into the LAA; no residual stumps were noted. Two patients (2.7%) had undetermined flow. We have demonstrated excellent success with RLAAC; we postulate that this may be due to improved intracardiac visualization. Robotic LAA closure was more successful (87.7%) than previously reported results from the Left Atrial Appendage Occlusion Study for suture exclusion (45.5%) and staple closure (72.7%). With success rates equivalent to transcatheter device closures, RLAAC should be considered for robotic mitral valve surgical patients.

Rationale and trial design of the Left Atrial Appendage Occlusion Study (LAAOS III)

Objectives: Stroke prevention in atrial fibrillation (AF) may be achieved by elimination of AF itself, prevention of clot formation by medical therapy and physical elimination of the left atrial appendage (LAA), the site of clot formation. Elimination of AF has actually not been effective against stroke, probably because no AF therapy has been able to suppress all AF episodes. Anticoagulant therapy is effective, but is limited by bleeding, patient non-compliance, suboptimal anticoagulation control and need for therapy discontinuation during lifelong treatment. Occlusion of the LAA is a logical idea that has received considerable recent attention due to positive results from a small trial of device closure.

Left atrial appendage occlusion in atrial fibrillation after intracranial hemorrhage

To evaluate the safety and feasibility of percutaneous left atrial appendage occlusion (LAAO) in patients with atrial fibrillation (AF) and previous intracranial hemorrhage (ICH). In an explorative, prospective, single-center, observational study, LAAO was performed in patients with previous ICH and AF using the Amplatzer Cardiac Plug device. Risks of ischemic strokes and hemorrhagic complications were estimated using the CHA2DS2Vasc score and the HAS-BLED score. Before and 1, 6, 12, and 24 months after the procedure, clinical status and complications were recorded. Major complications were predefined as periprocedural stroke, death, pericardial effusion, and device embolism. LAAO was performed in 20 patients. Based on CHA2DS2Vasc score (mean 4.5 ± 1.4) and HAS-BLED score (mean 4.7 ± 1.0), annual risks of stroke and hemorrhagic complications were 4.0%-6.7% and 8.7%-12.5%, respectively. No patient had a procedure-related complication. Minor postprocedural complications were observed in 4/20 patients (2 inguinal hematoma, 1 self-limiting asystole, and 1 thrombus formation on device). No ischemic or hemorrhagic stroke occurred during a mean follow-up of 13.6 ± 8.2 months. In this first study of LAAO in patients with previous ICH, LAAO appears feasible and safe. A larger, controlled trial is needed to assess the efficacy and safety of the procedure compared to other preventive measures. This study provides Class III evidence that in patients with a history of previous ICH and AF, percutaneous LAAO is safe and feasible.

Left Atrial Appendage Occlusion Study II (LAAOS II)

BackgroundOcclusion of the left atrial appendage (LAA) is a potential alternative to anticoagulation for patients with atrial fibrillation (AF); however, evidence of its safety and efficacy is lacking. The Left Atrial Appendage Occlusion Study II (LAAOS II) explored the feasibility of a definitive trial of LAA occlusion for stroke prevention in AF. MethodsA cross-sectional study of 1889 consecutive patients undergoing cardiac surgery was performed to determine the prevalence of AF and risk factors for stroke. We also randomized 51 patients with AF and increased stroke risk to LAA occlusion (n = 26) or no occlusion and oral anticoagulation (n = 25) to assess the rate of recruitment and the safety of LAA amputation. ResultsIn the cross-sectional study, 204 patients (10.8%) had AF and 98 (5.2%) met trial eligibility. Fifty-one patients were recruited into the trial at a rate of 1.6 patients per centre per month. No patient with occlusion had significant bleeding at the LAA site. At 1 year, 4 patients (15.4%) in the occlusion arm and 5 patients (20.0%) in the no-occlusion arm experienced death, myocardial infarction (MI), stroke, noncerebral systemic emboli, or major bleeding (relative risk [RR], 0.71; 95% confidence interval [CI], 0.19-2.66; P = 0.61). The predominant component of the composite was stroke, with 1 in the occlusion arm and 3 in the no-occlusion arm. ConclusionsLAA occlusion can be safely performed at the time of cardiac surgery. A large trial to evaluate the clinical efficacy of LAA occlusion in patients undergoing cardiac surgery is possible in motivated centres with some modifications to the design of LAAOS II.

Left Atrial Appendage Occlusion Study (LAAOS): Results of a randomized controlled pilot study of left atrial appendage occlusion during coronary bypass surgery in patients at risk for stroke

This pilot study assessed the safety and efficacy of left atrial appendage (LAA) occlusion, performed at the time of coronary artery bypass grafting (CABG). At the time of CABG, 77 patients with risk factors for stroke were randomized to LAA occlusion or control. The LAA was occluded using sutures or a stapling device. Completeness of occlusion was assessed with transesophageal echocardiography. There were no significant differences in cardiopulmonary bypass duration, perioperative heart failure, atrial fibrillation, or bleeding between the 2 groups. During surgery, there were 9 appendage tears, all of which were repaired easily with sutures. Among patients having a postoperative transesophageal echocardiography, complete occlusion of the LAA was achieved in 45% (5/11) of cases using sutures and in 72% (24/33) using a stapler, P = .14. The rate of LAA occlusion by individual surgeons increased from 43% (9/21) to 87% (20/23) after performing 4 cases (P = .0001). After a mean follow-up of 13 +/- 7 months, 2.6% of patients had thromboembolic events. LAA occlusion at the time of CABG is safe. The rate of complete occlusion improves, to acceptable levels, with increased experience and the use of a stapling device. A large trial is needed to determine if LAA occlusion prevents stroke.

Left Atrial Appendage Occlusion Study (LAAOS): A randomized clinical trial of left atrial appendage occlusion during routine coronary artery bypass graft surgery for long-term stroke prevention

Background Many patients undergoing coronary artery bypass graft (CABG) surgery have risk factors for both atrial fibrillation (AF) and stroke. The left atrial appendage (LAA) is a main source of thrombus coming from the left atrium. LAA occlusion should be tested as a means to reduce future cerebral ischemic events in these patients. Methods The Left Atrial Appendage Occlusion Study (LAAOS) is a randomized clinical trial designed to evaluate the feasibility, safety, and efficacy of LAA occlusion for prevention of ischemic stroke in patients undergoing CABG. The target population consists of patients at risk of AF and stroke who are having routine CABG surgery. The main study will be a prospective, controlled, unblinded trial. Patients at risk of future development of AF, or having AF, will be randomly assigned to undergo or not undergo LAA occlusion. A total of 2500 patients will be randomly assigned and followed for 5 years for the primary outcome of stroke. This study of 2500 patients will have 90% power to detect a relative reduction of 20% in stroke, from a 5-year incidence of 20% in the control group to 16% in the intervention group. Currently, a pilot trial is underway that will enroll 100 patients to assess feasibility, safety, and rates of successful LAA occlusion as assessed by postoperative transesophageal echocardiography. The most suitable surgical technique will also be assessed during the pilot trial. In the pilot study, the main outcomes are safety and rate of successful obliteration of the LAA after surgical occlusion. Conclusions The clinical trial designed to evaluate LAA occlusion at the time of routine CABG surgery is currently in the pilot phase. (Am Heart J 2003;145:174-8.)