Author + information
- Received December 7, 2015
- Revision received March 15, 2016
- Accepted April 19, 2016
- Published online July 11, 2016.
- Konstantinos C. Koskinas, MD, MSca,
- Samera Shakir, MDa,
- Máté Fankhauser, MSa,
- Fabian Nietlispach, MDb,
- Adrian Attinger-Toller, MDb,
- Aris Moschovitis, MDa,
- Peter Wenaweser, MDa,
- Thomas Pilgrim, MDa,
- Stefan Stortecky, MDa,
- Fabien Praz, MDa,
- Lorenz Räber, MDa,
- Stephan Windecker, MDa,
- Bernhard Meier, MDa and
- Steffen Gloekler, MDa,∗ ()
- aCardiology, Cardiovascular Department, University Hospital of Bern, Bern, Switzerland
- bCardiology, University Hospital of Zurich, Zurich, Switzerland
- ↵∗Reprint requests and correspondence:
Dr. Steffen Gloekler, University Hospital of Bern, Department of Cardiology, Bern, Switzerland.
Objectives The aim of this study was to assess predictors of adverse 1-week outcomes and determine the effect of left atrial appendage (LAA) morphology following LAA closure (LAAC) with Amplatzer devices.
Background Percutaneous LAAC is a valuable treatment option for stroke prevention in patients with atrial fibrillation. Determinants of procedural safety events with Amplatzer occluders are not well established, and the possibly interrelating effect of LAA anatomy is unknown.
Methods Between 2009 and 2014, 500 consecutive patients with atrial fibrillation ineligible or at high risk for oral anticoagulation underwent LAAC using Amplatzer devices. Procedure- and device-related major adverse events (MAEs) were defined as the composite of death, stroke, major or life-threatening bleeding, serious pericardial effusion, device embolization, major access-site vascular complication, or need for cardiovascular surgery within 7 days following the intervention.
Results Patients (mean age 73.9 ± 10.1 years) were treated with Amplatzer Cardiac Plug (n = 408 [82%]) or Amulet (n = 92 [18%]) devices. Early procedural success was 97.8%, and MAEs occurred in 29 patients (5.8%). Independent predictors of MAEs included device repositioning (odds ratio: 9.13; 95% confidence interval: 2.85 to 33.54; p < 0.001) and left ventricular ejection fraction <30% (odds ratio: 4.08; 95% confidence interval: 1.49 to 11.20; p = 0.006), with no effect of device type or size. Angiographic LAA morphology, characterized as cauliflower (33%), cactus (32%), windsock (20%), or chicken wing (15%), was not associated with procedural success (p = 0.51) or the occurrence of MAEs (p = 0.78).
Conclusions In this nonrandomized study, procedural success of LAAC using Amplatzer devices was high. MAEs within 7 days were predicted by patient- and procedure-related factors. Although LAA morphology displayed substantial heterogeneity, outcomes were comparable across the spectrum of LAA anatomies.
Although oral anticoagulation (OAC) is currently the standard treatment for stroke prevention in patients with atrial fibrillation (AF), OAC is frequently contraindicated or insufficiently controlled (1), it entails an inherent bleeding risk (2), and it is discontinued in up to 50% of patients within 3 years of treatment initiation (3). Because >90% of cardiac thrombi form in the left atrial appendage (LAA) in patients with nonvalvular AF (4), catheter-based LAA closure (LAAC) has emerged as a valuable nonpharmacological treatment alternative and is advocated as a potential therapeutic option in current guidelines (5).
Randomized trials established the superiority of LAAC with the Watchman device (Boston Scientific, Natick, Massachusetts) over warfarin for long-term stroke prevention and reduction of mortality (6). Previous studies with Amplatzer LAA occluders (St. Jude Medical, St. Paul, Minnesota) (7–11) showed the feasibility of the intervention but were limited by small sample sizes, assessed patients treated with dedicated or nondedicated devices (10), and included centers with variable operator experience (11)—factors known to affect LAAC outcomes (12). Although some concerns have been expressed regarding the rate of early safety events following LAAC procedures, little is known about patient-, device-, and procedure-related predictors of periprocedural complications of LAAC. Moreover, whether procedural outcomes with Amplatzer devices may be influenced by LAA morphology remains unknown despite the fact that LAA structure is highly heterogeneous, affects the propensity to thrombotic complications in patients with AF (13,14), and modifies device healing responses upon LAAC in pre-clinical models (15).
The purposes of this observational study were to determine predictors of early (1-week) outcomes of LAAC using Amplatzer devices and to investigate the association of LAA morphology with procedural performance and early safety events. We therefore analyzed a sizable cohort of consecutively enrolled patients undergoing LAAC with dedicated Amplatzer devices at 2 high-volume centers.
All consecutive patients who were scheduled for LAAC between 2009 and 2014 at 2 Swiss centers, the Bern and Zurich University hospitals, were enrolled in this prospective observational registry. In line with current recommendations (5,16), we included a wide range of patients with AF with moderate to high thromboembolic risk who had absolute or relative contraindications to OAC, were deemed by their physicians to be at high risk for long-term OAC treatment (including indication for triple antithrombotic therapy in view of the necessity of dual-antiplatelet therapy, e.g., because of previous or planned percutaneous coronary interventions [PCI]), or preferred an alternative to OAC. The study was approved by the local ethics committees.
Device characteristics and procedural aspects were previously described in detail (16,17). Procedures were performed by experienced operators mostly under fluoroscopic guidance using dedicated Amplatzer devices (first-generation Amplatzer Cardiac Plug [ACP] and second-generation Amulet). LAAC was performed either alone, possibly combined with diagnostic coronary angiography (“lone LAAC”), or in combination with concomitant procedures, including PCI, closure of patent foramen ovale (PFO) or atrial septal defect, transcatheter aortic valve replacement, mitral clip insertion, or AF ablation (“combined interventions”). The left atrium was accessed by means of transseptal puncture in the majority of patients or through a PFO or atrial septal defect, if deemed feasible (18). According to manufacturer instructions, device oversizing of 3 to 5 mm for the ACP and 2 to 4 mm for the Amulet, relevant to the landing zone (defined fluoroscopically and on pre-procedural transesophageal echocardiography), was typically applied. Device repositioning was defined as partial recapture of the same device, whereas change of device was defined as full recapture and switch to a new device size.
Antithrombotic treatment was not pre-specified but left at the discretion of treating operators for each individual patient, and it typically consisted of uninterrupted periprocedural OAC if previously administered. Consistent with manufacturer recommendations as well as with previous evidence with Amplatzer occluders (8,11), OAC was discontinued immediately following successful LAAC, and dual-antiplatelet therapy was initiated, consisting of aspirin 100 mg for at least 5 months and clopidogrel 75 mg for 1 to 6 months.
Clinical endpoints and definitions
Demographic, clinical, and procedural characteristics were prospectively collected in a dedicated database. Early procedural success was defined as successful implantation of the device in the LAA. Clinical endpoints were predefined according to VARC 2 (Valve Academic Research Consortium 2) criteria (19). The study’s primary endpoint was the combined safety endpoint of device- and procedure-related major adverse events (MAEs) during hospitalization or within 7 days post-procedure, whichever occurred later. In the absence of an established composite endpoint for LAAC, MAEs were defined to include serious safety events, taking into account reporting in previous studies. MAEs included death, stroke, procedure-related major or life-threatening bleeding, device embolization, major access-vessel complication, need for cardiovascular surgery, need for cardiopulmonary resuscitation, and serious pericardial effusion (i.e., hemodynamically significant effusion prompting intervention or resulting in prolonged hospitalization). All events were adjudicated, and relatedness to the device or procedure was determined by an independent clinical events committee consisting of 2 cardiologists and, in case of disagreement, by a third referee.
LAA morphological assessment
Morphological LAA characterization was performed on the basis of angiography in right and left anterior oblique projections by investigators blinded to patient history and outcomes. LAA morphology was characterized as cauliflower (limited overall length with more complex internal structures), windsock (with 1 dominant lobe of sufficient length as the primary structure and secondary or even tertiary lobes), cactus (sufficient length with a dominant central lobe with secondary lobes extending from the central lobe), or chicken wing (sufficient length with obvious bend in the proximal part of the dominant lobe or folding back of the LAA anatomy at some distance from the LAA ostium) (13,14). To determine interobserver reproducibility, 40 randomly selected patients were analyzed by 2 assessors blinded to initial classification, and Cohen’s kappa was calculated.
Statistical analyses were performed with SPSS version 17.0 software (SPSS, Inc., Chicago, Illinois). Categorical variables are presented as actual numbers and percentages and were compared with chi-square or Fisher exact tests. Continuous variables are summarized as mean ± SD and were compared using Student t tests or Wilcoxon rank sum tests. Predictors of MAEs were determined by univariate logistic regression analysis; variables with significant univariate effects (p < 0.10) were retained in the multivariate regression model. Estimates of the odds ratios (OR) and 95% confidence intervals (CI) for each variable are presented. The interobserver agreement for LAA morphological characterization was assessed using Cohen’s kappa statistic, with a good level of agreement defined by κ >0.61 (20). Findings were considered statistically significant at the 0.05 level.
Baseline and procedural characteristics
A total of 500 consecutive patients were included in this study. Baseline characteristics are summarized in Table 1. The mean CHADS2 score was 2.6 ± 1.3, the mean CHA2DS2-VASc score was 4.3 ± 1.7, and the mean HAS-BLED score was 2.9 ± 1.1. Previous history of stroke was present in 30.1% of patients. Indication for LAAC was absolute or relative contraindication to OAC in 419 patients (84%) and LAAC as an alternative to OAC in 81 patients (16%); indications are detailed in Figure 1.
Procedural characteristics are summarized in Table 2. Early procedural success was 97.8%. Interventions were performed by means of transseptal puncture in 74% and via PFO or atrial septal defect in 26% of patients. The Amulet device was used in 92 patients (18%). The distribution of device sizes is shown in Figure 2. Changes of device size were required in 32 patients, including 4 patients with second changes of device size. A total of 536 devices were used (1.07 per patient). Repositioning of the initial device (partial recapture) was required in 20 patients (4%). Lone LAAC was performed in 242 patients (48.4%), and combined interventions were performed in 258 patients (51.2%), most frequently in combination with PCI or PFO closure (Table 2).
Outcomes within 7 days
Clinical outcomes are presented in Table 3. The primary endpoint, device- or procedure-related MAEs, occurred in 29 unique patients (5.8%). In several patients, more than 1 event occurred. Two patients died in the hospital (0.4%). VARC major or life-threatening bleeding occurred in 17 patients (3.4%) and pericardial effusion in 33 (6.6%), including serious effusions in 16 patients (3.2%). Stroke occurred in 5 patients (1%) (disabling stroke in 1 patient) due to embolization of air or thrombi. Device embolization occurred in 10 patients (2.0%) and was managed with percutaneous retrieval during the index procedure in 7 patients and with subsequent percutaneous or surgical retrieval in 3 patients. Device oversizing was numerically, but not significantly, lower in patients with versus without device embolization (13.1 ± 8.6% vs. 26.4 ± 14.2%; p = 0.11).
Patients with versus without MAEs more commonly had left ventricular ejection fractions (LVEFs) <30% (24.1% vs. 5.9%; p < 0.001) (Table 1), received similar device sizes (Figure 2), but had lower implantation success rates (Table 2). Univariate predictors of MAEs included LVEF <30%, OAC treatment at baseline, device repositioning (partial recapture), and change of device size during the intervention (Table 4). Device repositioning (OR: 9.13; 95% CI: 2.85 to 33.54; p < 0.001) and LVEF <30% (OR: 4.08; 95% CI: 1.49 to 11.20; p = 0.006) remained independent predictors of MAEs in multivariate analysis (Table 4).
The ACP compared with the Amulet device did not differ regarding early procedural success (97.5% vs. 98.9%; p = 0.43), MAEs (5.6% vs. 6.5%; p = 0.74), or any periprocedural complications (Online Table 1).
Combined interventions versus lone LAAC were not unexpectedly associated with greater contrast medium volume (274 ± 105 ml vs. 182 ± 83 ml; p < 0.001) and fluoroscopy time (24.2 ± 14.2 min vs. 15.2 ± 12.9 min; p < 0.001). There was no difference with respect to early procedural success (98.4% vs. 97.1%; p = 0.11) or rates of MAEs (5% vs. 6.6%; p = 0.47) for combined versus lone LAAC (Online Table 2). In an ancillary analysis focusing only on patients who underwent lone LAAC, predictors of MAEs were similar as in the entire cohort (device repositioning, p = 0.02; lower LVEF, p = 0.07).
An analysis comparing the first 250 consecutive versus the subsequently enrolled 250 patients found no difference in early procedural success (98% vs. 97.6%; p = 0.78) or in the rate of MAEs (6% vs. 5.6%; p = 0.85). Figure 3 summarizes the rate of MAEs stratified for patient- and device-related characteristics.
LAA morphology and procedural outcomes
Among patients with definable angiographic LAA morphology (477 of 500 [95%]), the most common type was cauliflower (33%), followed by cactus (32%), windsock (20%), and chicken wing shape (15%), with good interobserver agreement for classification (κ = 0.83; p < 0.001). Despite between-group variations, we found no statistically significant difference among LAA morphologies with regard to procedural success (p = 0.51), need for device repositioning (p = 0.58), device embolization (p = 0.42), or MAEs (p = 0.78) (Figure 4).
Catheter-based LAAC is increasingly recognized as a valuable treatment option for stroke prophylaxis in patients with AF (6,16,21); however, concern has been raised regarding the procedural safety of this preventive intervention. In the present study, we analyzed a sizable cohort of consecutive patients undergoing LAAC with dedicated Amplatzer devices, focusing on early (1-week) adverse outcomes and their predictors. We found high early procedural success and rates of major complications that are comparable with those found in previous observational studies with Amplatzer devices. Early safety events were associated with patient- and procedure-related factors, including depressed LVEF and need for device repositioning. Although LAA morphology displayed substantial heterogeneity, clinical outcomes were comparable across the spectrum of LAA anatomies.
Successful device deployment was high (97.8%), although complete LAAC may be overestimated in the absence of periprocedural transesophageal echocardiographic assessment. The rate of MAEs within 7 days was 5.8% in this study. Previous observational studies with Amplatzer occluders reported early major event rates events of 7% in the initial European experience report (7), 5.8% for in-hospital events (8), and 5% in the multicenter Amplatzer registry (11), although different definitions of MAEs were applied. In randomized trials with the Watchman device, early adverse events were more frequent at initial stages and declined with growing operator experience (12); direct comparison with the present study is not feasible in view of differences in study design, device characteristics, and included patient populations. Taken together, the findings of the present as well as previous studies suggest nonnegligible rates of early safety events and thus point to the potential value of identifying predictive factors of early complications.
Predictors of periprocedural adverse outcomes following LAAC are not well established, with the exception of a marked effect of operator experience (12). This study explored correlates of early safety events with Amplatzer occluders. The need for device recapture and repositioning, a maneuver likely reflecting complex and technically challenging anatomies, was the strongest predictor of MAEs. Depressed LVEF, a factor previously associated with early PCI outcomes (22) as well as longer term adverse outcomes following LAAC (8), also emerged as a predictor of MAE in this cohort. Baseline OAC treatment was a univariate predictor of MAE but an independent predictor specifically of major or life-threatening bleeding events (i.e., the most frequent MAE in this cohort (Online Table 3). Although femoral venous puncture per se does not necessitate OAC withdrawal, LAAC is an intervention with bleeding-prone steps, such as transseptal puncture, insertion of large-caliber sheaths, and potential injury of the thin-walled LAA structure. Therefore, unlike current recommendations for PCI (23), uninterrupted OAC may not be an appropriate strategy for LAAC interventions. Although the lower magnitude of device oversizing in patients with device embolization was formally not significant (p = 0.11), it is a notable finding that reflects the importance of appropriate device sizing and requires further investigation.
Unlike previous studies (12,24), a learning-curve effect as it relates to the occurrence of MAEs was not observed in the present study. This is likely because LAAC interventions have been performed at our institutions since 2002 (10), whereas the present registry was initiated only in 2009. Along these lines, the present observations from 2 experienced centers may not be directly applicable to other sites with varying levels of operator and institutional experience with the procedure and the specific devices.
LAA morphology displays substantial variations that have been associated with the risk for thromboembolic complications in patients with AF (13,14). Whether LAA morphology affects early LAAC outcomes has not been previously assessed. We found comparable procedural success and early adverse events across LAA morphologies. This finding is in keeping with the design of Amplatzer occluders, featuring a proximal disc (intended to provide ostial LAA sealing) and a flexible waist that facilitates conformation of the distal lobe to variable appendage shapes (16). On the basis of the hypothesis-generating findings of this study derived from crude, 2-dimensional angiographic evaluations, further studies are warranted to assess the impact of LAA morphology on LAAC outcomes using more refined modalities, also examining other devices.
Compared with the ACP, the Amulet design entails modifications to facilitate the implantation process, improve stability, and minimize complications, including a wider lobe, a recessed proximal end screw, and more stabilizing wires (16). The ACP and Amulet devices were associated with comparable early outcomes in this study, although this finding should be interpreted cautiously in view of the observational nature of the study. The present analysis represents the largest experience to date with the Amulet device and adds to previous preliminary investigations, which also showed nondiffering outcomes with the 2 devices (25).
Certain technical aspects of the intervention applied in this cohort may limit the generalizability of the present findings. Although interventions performed under fluoroscopic-only guidance simplify procedural logistics (fewer personnel, possibility to avert sedation and intubation), procedural transesophageal echocardiographic guidance during LAAC is preferred in most centers (16) and is recommended in professional position papers (21). Whether transesophageal echocardiography–guided interventions or pre-procedural LAA imaging using more refined methodologies (e.g., 3-dimensional transesophageal echocardiography or computed tomographic angiography) (26) might have resulted in fewer MAEs cannot be determined in the present dataset. Along the same lines, although access to the LAA through a PFO appears to be technically feasible, it may lead to suboptimal delivery sheath alignment with the LAA (16,17) and therefore is typically avoided and not routinely recommended (21).
Combined interventions, performed in one-half of patients in this cohort, were not associated with higher rates of MAE, but this finding requires cautious interpretation in view of the marked heterogeneity of interventions and the nonrandomized nature of this study. Although such an approach appears to be feasible in the given setting, the advantage of avoiding subsequent hospitalizations for staged procedures needs to be carefully examined on an individual basis, accounting for patient safety, operator experience, and complexity of interventions. Properly designed prospective studies are planned to compare LAAC performed alone versus combined with specific cardiac interventions. The possibly confounding effect of combined interventions on our predictor analyses is acknowledged, but we believe that it is minimized by the identification of similar predictors of MAEs in patients who underwent lone LAAC as in the entire cohort.
Comorbidities were frequent in the present all-comers cohort, including patients with depressed LVEFs, who have typically been excluded from previous LAAC studies. The risk for stroke was moderately high (mean CHADS2 score 2.6), comparable with that observed in nonrandomized studies with Amplatzer (11) or Watchman devices (27) but somewhat higher than in the PROTECT AF (Watchman Left Atrial Appendage System for Embolic Protection in Patients With AF) randomized trial (6). Two-thirds of patients in this cohort had high bleeding risk (HAS-BLED score >3), a proportion that is greater than in most previous studies of LAAC (26). The majority of patients in this study (84%) had relative or absolute contraindications to OAC, similar to earlier nonrandomized investigations (8,28). Although randomized trials of the Watchman device tested LAAC exclusively as an alternative to OAC (i.e., in patients eligible for OAC) (12,24), contraindication to OAC is a frequent reason for LAAC in clinical practice (16) and is advocated in current position papers (5).
Direct comparison of the present findings with those of previous reports assessing early outcomes of LAAC interventions is limited by somewhat differing definitions of serious safety events. In this study, the broadly inclusive definition of MAEs focused on early safety events deemed to be related to the intervention. Unlike the present analysis, percutaneous snaring of embolized devices and drainage of pericardial effusions were not included in the early safety endpoint of the randomized PREVAIL (Prospective Randomized [2:1] Evaluation of the Watchman LAA Closure Device in Patients With Atrial Fibrillation Versus Long Term Warfarin Therapy) trial (24). Similar to other cardiac interventions (19), standardized endpoints for LAAC interventions are required to facilitate direct comparison of outcomes in future studies.
This study provides novel insights regarding correlates of early safety events following LAAC with Amplatzer devices. An enhanced understanding of factors associated with unfavorable procedural outcomes may allow better risk stratification and thereby expand the population of patients who are likely to benefit from the intervention. Similar to the present study focusing on early outcomes, longer term outcomes of LAAC with Amplatzer occluders have been assessed only in observational studies (7–11); randomized trials are needed to address early and long-term safety and efficacy following LAAC with these devices.
This study had several limitations attributable to its observational design. Although data were prospectively collected, this was a retrospective analysis without independent monitoring and core laboratory analyses. While multivariate adjustments were performed to identify independent predictors of outcomes, the effect of unmeasured baseline confounders cannot be excluded. The possibility of type II error due to multiple comparisons cannot be ruled out. Despite the large number of consecutively enrolled patients, the study may have been underpowered to fully explore predictors of early adverse events because of the relatively small absolute number of MAEs. Our observations may not be directly applicable to patient populations with different proportions of baseline OAC treatment or differing periprocedural antithrombotic management. Patients receiving non–vitamin K oral anticoagulants were underrepresented in this cohort. As in the case of more sophisticated modalities for assessment of LAA structure (13,14), we cannot exclude some overlap of LAA morphological types defined angiographically in this study; these concerns are minimized, however, by the good reproducibility of classifications and the exclusion from the analyses of uncertain cases. Whether our findings are generalizable to other devices is unclear; although a systemic review of observational studies found no device-specific differences regarding early safety of LAAC (29), direct randomized comparison of Amplatzer occluders (currently not marketed in the United States) with the U.S. Food and Drug Administration–approved Watchman devices is required to definitively address this issue.
In this sizable population of consecutive patients, procedural success of LAAC using Amplatzer devices was high. MAEs within 7 days were predicted by patient- and procedure-related factors. Although LAA morphology displayed substantial heterogeneity, outcomes were comparable across the spectrum of LAA anatomies.
WHAT IS KNOWN? Percutaneous LAAC is a reasonable alternative to OAC therapy in patient with AF. Predictors of periprocedural adverse events are not well established.
WHAT IS NEW? Early procedural success of LAAC with Amplatzer devices was high in this study (97.8%). MAEs within 7 days were predicted by patient- and procedure-related factors and did not differ across variable LAA morphologies.
WHAT IS NEXT? Further data from randomized studies will be required to assess early and longer term outcomes of LAAC with these devices.
Prof. Meier is a consultant to and has received grants to the institution from St. Jude Medical. Prof. Windecker has received grants to the institution from Abbott, Biotronik, Boston Scientific, Medtronic, Edwards Lifesciences, and St Jude Medical. Dr. Nietlispach is a consultant to St. Jude Medical, Edwards Lifesciences, Direct Flow Medical, and Medtronic. Dr. Gloekler has received a grant from the Swiss Heart Foundation. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose. Drs. Koskinas and Shakir contributed equally to this work.
- Abbreviations and Acronyms
- Amplatzer Cardiac Plug
- atrial fibrillation
- left atrial appendage
- left atrial appendage closure
- left ventricular ejection fraction
- major adverse event(s)
- oral anticoagulation
- percutaneous coronary intervention
- patent foramen ovale
- Received December 7, 2015.
- Revision received March 15, 2016.
- Accepted April 19, 2016.
- American College of Cardiology Foundation
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