Surgical Left Atrial Appendage Occlusion in Patients with Atrial Fibrillation Undergoing Mechanical Heart Valve Replacement
Atrial fibrillation (AF) is the most common cardiac arrhythmia, affecting millions of people worldwide. It is associated with a significantly increased risk of stroke and systemic embolism, primarily due to thrombus formation in the left atrial appendage (LAA). Surgical left atrial appendage occlusion (SLAAO) has been proposed as a potential strategy to reduce the risk of thromboembolic events in patients with AF undergoing cardiac surgery. However, the effectiveness of SLAAO in patients undergoing mechanical heart valve replacement (MHVR) remains unclear. This study aimed to evaluate the association between SLAAO and cardiovascular outcomes in patients with AF undergoing MHVR.
Background and Rationale
AF is a major risk factor for stroke, with the LAA being the primary source of thrombus formation in non-valvular AF. The LAA is also implicated in a significant proportion of thromboembolic events in valvular AF. Given the high risk of stroke in AF patients, strategies to reduce thromboembolic events are of paramount importance. While anticoagulation therapy is the cornerstone of stroke prevention in AF, surgical occlusion of the LAA has been explored as an adjunctive measure, particularly in patients undergoing cardiac surgery.
SLAAO can be performed using various techniques, including suture exclusion, stapler exclusion, snares, or epicardial clips. Theoretically, SLAAO should reduce the risk of thromboembolism by eliminating the primary site of thrombus formation. However, the procedure is not without risks, including prolonged operative times, potential damage to surrounding structures, and incomplete occlusion of the LAA. Despite these concerns, SLAAO has been recommended in recent European and American guidelines for certain patients undergoing cardiac surgery.
Previous studies have reported mixed results regarding the effectiveness of SLAAO in reducing thromboembolic events. Some studies have suggested that SLAAO is associated with a lower risk of stroke and mortality, while others have found no significant benefit. Importantly, most of these studies have included a relatively small proportion of patients undergoing MHVR, leaving a gap in the evidence regarding the effectiveness of SLAAO in this specific population.
Study Design and Methods
This study was a single-center, retrospective, observational analysis conducted at Fuwai Hospital in Beijing, China. The study enrolled 497 consecutive adult patients with AF who underwent MHVR between July 1, 2017, and June 30, 2018. Patients who had undergone prior open-heart valve surgery, coronary artery bypass grafting (CABG), or AF ablation procedures were excluded. The study population was divided into two groups: those who underwent concomitant SLAAO (27.6%) and those who did not (No-SLAAO group).
Baseline demographic and clinical data were collected, including age, sex, body mass index (BMI), comorbidities, and surgical details. The primary outcome was a composite of ischemic stroke, systemic embolism, and all-cause mortality. Secondary outcomes included hemorrhagic events and a composite of ischemic stroke, systemic embolism, major bleeding, and all-cause mortality. In-hospital complications, such as 30-day mortality, re-exploration, and acute kidney injury, were also assessed.
SLAAO was performed using one of three techniques: intra-atrial oversewing, epicardial ligation, or amputation. The completeness of SLAAO was visually assessed by the surgeons. All patients were prescribed warfarin postoperatively, with a target international normalized ratio (INR) range of 1.8 to 2.5.
Statistical Analysis
Continuous data were expressed as mean ± standard deviation or median (interquartile range), and categorical variables were presented as counts with percentages. Differences between groups were tested using t-tests, Wilcoxon rank-sum tests, Chi-squared tests, or Fisher exact tests, as appropriate. Kaplan-Meier curves were used to estimate cumulative event-free survival rates, and log-rank tests were used to compare the curves. Multivariate Cox proportional hazards regression models were used to evaluate the association between SLAAO and outcomes.
To address potential confounding, propensity score matching (PSM) was performed to balance baseline characteristics between the SLAAO and No-SLAAO groups. One-to-one nearest-neighbor matching was used, and standardized differences were calculated to assess balance. Subgroup analyses were conducted to explore the impact of SLAAO in different patient populations, stratified by sex, BMI, CHA2DS2-VASc score, coronary artery disease, and left atrial dimension.
Results
The mean age of the study cohort was 55.9 years, and 61.8% of the patients were women. Rheumatic heart disease was the most common indication for MHVR, with most patients undergoing mitral valve replacement or double-valve replacement. Patients in the SLAAO group were more likely to have an atrial thrombus, rheumatic mitral valve disease, and mitral stenosis compared to the No-SLAAO group.
In the overall cohort, five patients died within 30 days postoperatively, with no significant differences in in-hospital complications between the two groups. After a median follow-up of 14 months, 14 primary events occurred. Kaplan-Meier curves showed no significant differences in the cumulative incidence of the primary outcome, hemorrhagic events, or the secondary outcome between the SLAAO and No-SLAAO groups. Multivariate Cox regression analysis also found no significant association between SLAAO and any of the outcomes.
After PSM, 120 matched pairs were analyzed. The SLAAO group had significantly longer cardiopulmonary bypass (CPB) times, aortic cross-clamp times, and postoperative lengths of stay compared to the No-SLAAO group. However, there were no significant differences in in-hospital complications or follow-up outcomes between the matched groups.
Subgroup Analyses
Subgroup analyses stratified by sex, BMI, CHA2DS2-VASc score, coronary artery disease, and left atrial dimension showed consistent results with the main findings. There were no significant interactions between SLAAO and any of the subgroup variables, indicating that the lack of benefit from SLAAO was consistent across different patient populations.
Discussion
This study found that concomitant SLAAO during MHVR was associated with longer operative times and postoperative lengths of stay but did not provide additional protection against thromboembolic events or mortality during the 14-month follow-up period. These findings suggest that SLAAO may not be necessary in patients with AF undergoing MHVR who are already receiving lifelong anticoagulation therapy.
The results of this study are consistent with some previous research that found no significant benefit of SLAAO in reducing thromboembolic events in patients receiving anticoagulation therapy. However, they contrast with other studies that reported a lower risk of stroke and mortality with SLAAO. The discrepancy may be due to differences in study populations, surgical techniques, and the quality of anticoagulation therapy.
One potential explanation for the lack of benefit observed in this study is that anticoagulation therapy with warfarin may already provide sufficient protection against thromboembolic events in patients with AF undergoing MHVR. In such cases, the additional risk reduction from SLAAO may be minimal. This is supported by the fact that all patients in this study were prescribed warfarin postoperatively, with a target INR range of 1.8 to 2.5.
Another consideration is the potential risks associated with SLAAO, including prolonged operative times, incomplete occlusion of the LAA, and the possibility of damage to surrounding structures. In this study, the SLAAO group had significantly longer CPB times and aortic cross-clamp times, which may increase the risk of perioperative complications. Additionally, incomplete occlusion of the LAA has been associated with an increased risk of thromboembolic events in some studies.
The LAA also plays a role in maintaining systemic homeostasis, including its electrical, mechanical, and neurohormonal functions. Occlusion of the LAA may disrupt these functions and potentially lead to adverse effects, such as an increased burden of subsequent AF. This is an important consideration when deciding whether to perform SLAAO in patients with AF undergoing MHVR.
Limitations
This study has several limitations. First, it was a retrospective, observational study, and treatment (SLAAO vs. No-SLAAO) was not randomly assigned. Although PSM was used to balance baseline characteristics, the potential for residual confounding cannot be ruled out. Second, the study may have been underpowered to detect differences in outcomes due to the relatively small number of events. Third, the study population was limited to patients with AF undergoing MHVR, and the results may not be generalizable to other patient populations. Fourth, the study did not capture information on adherence to anticoagulation therapy or INR values during follow-up, which may have influenced outcomes. Finally, the median follow-up period of 14 months may have been insufficient to detect long-term differences in outcomes.
Conclusion
In conclusion, this study found that concomitant SLAAO during MHVR was associated with longer operative times and postoperative lengths of stay but did not provide additional protection against thromboembolic events or mortality in patients with AF. These findings suggest that SLAAO may not be necessary in patients with AF undergoing MHVR who are already receiving lifelong anticoagulation therapy. Further studies with larger sample sizes and longer follow-up periods are needed to confirm these results and to evaluate the potential risks and benefits of SLAAO in this patient population.
doi.org/10.1097/CM9.0000000000000967
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