Percutaneous left atrial appendage closure (LAAC) has emerged as a suitable alternative for stroke prevention in non-valvular atrial fibrillation (AF) patients considered poor candidates for long – term oral anticoagulation ¹. Despite its efficacy, LAAC is not devoid of complications and can be associated with increased patient morbidity and mortality ²,³. Pericardial effusion, device embolization (DE), and device thrombosis are some of the complications that are infrequently associated with LAAC. Amongst these, DE is poorly understood with a reported incidence of <4% ⁴. Left atrial appendage (LAA) to device size mismatch and operator experience are believed to be the most common causes for DE ⁵. Currently, there is limited patient-level data regarding the clinical outcomes of patients who experience DE. We therefore sought to perform a retrospective analysis of LAAC DE cases from a worldwide multi-center experience to further understand the timing and clinical consequences of DE.

· Intraoperative device embolization: Event occurred during the procedure.

· Acute device embolization: Event diagnosed postoperatively within 24 hours.

· Subacute device embolization: Event diagnosed postoperatively after 24 hours but < 1 week

· Delayed device embolization: Event diagnosed any time after 1 week post-procedure.

· Major complication: DE that required (i) any cardiac intervention or surgery, (ii) resulted in damage to the surrounding cardiovascular structures, (iii) precipitated symptoms of angina, stroke, congestive heart failure, limb ischemia or heart block or (iv) resulted in the death of a patient.

· Minor complication: any other complication that did not meet the above criteria was considered minor complication.

· Percutaneous retrieval: was defined as device retrieval through a peripheral vascular access without any surgical cut-down.

· Surgical retrieval: was defined as any surgical technique that was used to retrieve the embolized device.

Continuous variables are expressed as mean ± standard deviation (SD) if normally distributed, and median ± Interquartile range (IQR) when deviations from normality were present. Categorical variables are expressed as counts and percentages. Categorical variables were compared between the groups using Chi-squared test or Fisher's Exact test. Continuous variables were compared using nonparametric test (Kruskal-Wallis Test). A two tailed p value <0.05 was considered statistically significant. Statistical analysis was performed using IBM SPSS Statistics version 23.0 (IBM, Armonk, New York).

This is the largest reported series of DE with LAAO to date. The main findings of this systematic review are: 1) the incidence of DE is 2% in our series; 2) DE occurred more frequently in the postoperative period and was associated with higher risk of serious complications, need for surgical retrieval and mortality compared with intraoperative DE; 3) operator reported device/LAA size mismatch is the most commonly identified factor associated with DE.

Earlier studies have reported that DE are more commonly observed intra-procedurally ⁵. On the contrary, in our study we found that more DE occurred post-procedurally. More than 50% of cases were recognized within the first 24 hours and 35% cases after one week. Embolized devices were found within the LA if recognized early and in the LV, LVOT, or aorta if found late.

The rate of major complications (including death) was significantly higher in postoperative DE cases compared to intraoperative DE. The need for surgical intervention and the rate of mortality significantly increased with LAAO DE occurring later from the time of deployment. All the complicated embolizations (100%, n=12/12) diagnosed more than 1 week after the procedure required surgical intervention and 33% of these resulted in mortality. This may relate to the fact that over time, the embolized device migrates out of the LAA and LA towards the mitral valve apparatus and LVOT. Devices in the LV are more likely to be trapped by the valves (mitral or aortic), both before and during the process of retrieval, requiring open surgical removal in most of the cases. Also, delay in recognition of LAAO DE prevents any prompt action until patient’s condition deteriorates and this can lead to increases in morbidity and mortality. Embolized ACP devices tended to locate in the LA (both intra and postoperatively) and also were less likely to require surgical intervention. This could perhaps be related to the design and structure of the device preventing it from going through the MV. In our study, we found that DE to LV and mitral valve apparatus were more likely to get complicated in comparison to other sites of embolization and were also more likely to require surgical intervention compared to other sites.

The goals of this study are to make operators aware of the timings, outcomes and complications involved with LAAODE. We highlighted the temporal and spatial association of LAAODE with clinical outcomes. An operator should maintain a high index of suspicion for LAAO DE for early recognition and mitigation of a complicated course. It is possible that a proportion of the post-operative DE occur within the first 24 hours but are only detected later during routine follow-up or when a patient becomes symptomatic. Routinely performing transthoracic echocardiography (TTE) within the first 24 hours (as early as 3-4 hours) following a procedure may help to identify and possibly minimize the complications of an acute DE. In our experience these devices are difficult to locate on Xray due to the lack of radiopaque materials in their construction. Future generation devices should include radiopaque materials to facilitate Xray localization. Due to the reported lag between time of actual embolization and time of diagnosis in some cases, consideration should be given to performing a TTE before the routine 1 month follow-up to identify any DE ⁶. Patient education regarding symptoms and signs of DE (unusual palpitations, congestive heart failure decompensation/shortness of breath, stroke/transient ischemic attack, limb ischemia) could also play an important role in early diagnosis. Early recognition is key in minimizing morbidity and mortality associated with DE.

Out study is limited by all the issues related to its retrospective observational nature. In addition, the rhythm at the time of embolization was not reported by the authors. Another limitation is residual confounding. Lastly, heterogeneities between operators, institutions and device specific variables could influence the LAAODE rates.

DE with percutaneous LAA occlusion is common with a reported incidence of 2% in our review. DE occurred more frequently in the postoperative period and was associated with higher risk of serious complications, need for surgical retrieval and mortality compared to intraoperative embolization.