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The authors report no relationships that could be construed as a
conflict of interest. This study was unfunded.
Background: In atrial fibrillation patients undergoing left atrial
appendage occlusion with a Watchman device, surveillance imaging with a
transesophageal echocardiogram (TEE) is typically performed at 45 days
and 1 year to evaluate for device-related thrombus (DRT) and peri-device
leak (PDL) before cessation of oral anticoagulation. The incidence of
these complications is relatively low, and the ideal timing and duration
of surveillance is unknown. We sought to evaluate the incidence of DRT
and PDL after Watchman placement at 45 days and 1 year to determine the
necessity of surveillance TEEs.
Methods: We retrospectively analyzed 361 patients who received a
Watchman device between January 2016 and January 2020. Baseline clinical
and echocardiographic data, post-procedure antithrombotic therapy and
surveillance echocardiographic data were collected from the NCDR LAAO
Registry. Nested backward variable elimination regression was performed
to derive independent predictors of the composite outcome of DRT and
PDL.
Results: A total of 286 patients who had post-procedure TEEs were
included in the analysis. At 45 days, 9 patients had DRT (3.2%) and 44
patients had PDL (15.0%). At 1 year, 5 patients had DRT (5.6%) and 8
patients had PDL (8.9%). All DRT at 45 days was treated with continued
anticoagulation while no change in protocol occurred with PDL. All DRT
at 1 year occurred in new patients without prior thrombus. A history of
prior transient ischemic attack (TIA) and thromboembolism were
significantly associated with DRT or PDL at 1 year.
Conclusions: We identified several patients with device-related
complications at 45 days and 1 year despite appropriate device sizing
and adequate use of antithrombotic therapy. The incidence of DRT
increased from 45 days to 1 year and occurred in patients without prior
thrombus. These findings highlight the importance of surveillance
imaging and suggest the potential need for extended surveillance in
select patients.
Keywords: Watchman, Surveillance, Transesophageal echocardiogram,
Device-related thrombus, Peri-device leak
Background
It is well-established that patients with non-valvular atrial
fibrillation and increased stroke risk benefit from anticoagulation with
a vitamin K antagonist or a direct oral anticoagulant. However long-term
oral anticoagulation increases risk of bleeding and therefore
percutaneous left atrial appendage occlusion (LAAO), such as the
Watchman device, has been incorporated into the guidelines as an
alternative for patients with increased stroke risk and
contraindications to anticoagulation.1 In patients
undergoing LAAO with a Watchman device, a transesophageal echocardiogram
(TEE) is typically performed at 45 days and 1 year to assess for
device-related complications including device-related thrombus (DRT) and
peri-device leak (PDL).2
While DRT is an uncommon finding after Watchman implantation with
studies reporting an incidence of 3-6%, it has been shown to be
associated with an increased risk of thromboembolic
events.3,4 A single center study showed that a short
course of warfarin successfully resolved all cases of DRT within 6
months without thrombus recurrence and with favorable clinical
outcomes.5 This highlights the importance of detection
and treatment of DRT. The incidence of PDL is highly variable, ranging
from 15 and 40%. PDL results in a persistent communication between the
LAA and the left atrium and therefore the systemic circulation,
potentially allowing thrombus within the LAA to be a source of embolic
events. Clinical trials have used a threshold of 5mm as a meaningful
leak requiring continued anticoagulation, however this is an arbitrary
number with inconsistent clinical implications.6 A
recent study showed that PDL greater than 3mm detected at 45 to 90 days
was associated with an increased risk of the combined outcome of failure
to stop anticoagulation, transient ischemic attack or stroke, DRT and
need for PDL closure.7 Additionally these
complications continue to occur during long-term follow-up after 12
months, although the clinical implications of these findings are
unclear.8
Amidst the ongoing coronavirus disease-2019 pandemic, the deferring of
aerosolizing elective procedures such as TEE has been examined to
prevent risk of viral transmission. In particular, the utility of 45-day
TEE after Watchman implantation was examined and showed a very low rate
of PDL and no DRT and therefore it was argued that it may be reasonable
to defer the 45-day TEE during the ongoing pandemic and potentially in
routine practice.9 While TEE is an overall low risk
procedure, it is still an invasive procedure and should only be
performed if clinically necessary. We sought to evaluate the incidence
of DRT and PDL after Watchman placement performed at a high-volume
center at 45 days and 1 year to determine the necessity and utility of
surveillance TEEs at these time points.
Methods
We retrospectively analyzed 361 patients who underwent Watchman device
placement between 2016 and 2020 and received surveillance TEE imaging
within 1 year. Baseline characteristics and echocardiographic data,
post-procedure anticoagulation/antiplatelet use, and surveillance TEE
data were collected from the NCDR LAAO Registry and patients’ electronic
medical records. Significant PDL was defined as >3mm color
jet seen on post-procedure TEE, defined based upon a recent study
showing higher risk of adverse outcomes with >3mm leak.
Categorical variables were analyzed using chi-square statistics, as
appropriate and continuous variables were analyzed using student T-test.
Nested backward variable elimination of non-significant variables at an
α-level >0.05 derived independent predictors of the
composite of DRT and PDL. SAS version 9.4 (SAS Institute Inc., Cary, NC)
was used for statistical analyses.
The Cedars-Sinai Institutional Review Board approved this retrospective
study and waived the requirement for individual patient informed
consent.
Results
A total of 286 patients who had post-procedure TEEs at 45 days were
included in the analysis, of which 96 had 1-year TEEs. Patients who did
not have 45-day follow-up with TEE were excluded (n=75). Demographic and
clinical characteristics and baseline echocardiographic data are
provided in Tables 1A and 1B . The mean age of the patient was
80 ± 8.7 years, 38% were female and
87% were white. The mean left ventricular ejection fraction was 56%
and mean CHA2DS2-VASc score was 4.4 ±
1.5. Upon discharge after the Watchman procedure, 261 patients (92%)
were discharged on at least 1 antiplatelet agent (92%) and 274 patients
(96%) were discharged on an anticoagulation agent (Table 2 ).
The follow-up TEE findings are described in Figure 1 . At 45
days, 44 patients had PDL ≥3mm (15%) and 9 patients had DRT (3%). At 1
year, 8 patients of 96 with TEE had PDL (8%) and 5 patients had DRT
(5%). All patients with PDL had a leak size ≤5mm at both 45 days and 1
year and presence of leak did not change management or effect duration
anticoagulation therapy. There was no progression of PDL at 1 year (no
leak increased in size to >5mm) and 8 patients with PDL had
improvement at 1 year. All DRTs at 45 days were treated with continued
anticoagulation and all with follow-up TEE at 1 year demonstrated
resolution. Of the available data at 1 year follow-up, 92 patients
(96%) were documented to be on least 1 antiplatelet agent. The 5 DRTs
demonstrated at 1 year occurred in patients who did not have prior
thrombi on imaging. A history of prior transient ischemic attack (TIA)
and prior thromboembolic event were independently associated with having
DRT or PDL at 1 year (both p=0.04).
Discussion
In this retrospective analysis we identified several patients with
device-related complications including DRT and PDL at 45 days and 1
year, despite appropriate use of antithrombotic therapy, suggesting that
performance of a low-risk TEE at these time points is still indicated
and can impact clinical management. The rate of PDL decreased over time
(15% to 8%) and there was no progression of PDL to >5mm
at 1 year despite no targeted therapy at the time PDL was discovered.
The rate of DRT increased slightly between 45 days and 1 year (3% to
5%) and of note all cases of DRT at 1 year did not have thrombus at 45
days suggesting that continued surveillance at least to 1 year appears
to be warranted. All DRTs were treated with continued anticoagulation at
45 days and resolved in those with follow-up imaging. All DRTs seen on 1
year TEE were in those without prior thrombus. Prior TIA and
thromboembolism were associated with the presence of device-related
complications at 1 year.
DRT is an important complication after percutaneous left atrial
appendage closure and is associated with higher risk of ischemic events
and the optimal postprocedural antithrombotic therapy and duration
remains unknown. The current evidence reports a 3-4% incidence, which
is consistent with our findings. Although the risk of DRT was thought to
be highest during early endothelization, there is increasing recognition
of late onset DRT with longer surveillance imaging which may be related
to delayed or incomplete endothelization of the
device.10,11 We showed that with appropriate treatment
of DRT detected at 45 days, there was complete resolution in those with
follow-up, which highlights the importance of early surveillance imaging
to guide appropriate therapy and prevent adverse events. Interestingly,
at 1 year there was a higher rate of DRT compared to at 45 days, and all
events occurred in patients without prior DRT. Importantly, none of the
patients with delayed DRT had undersized watchman devices (all devices
selected were 10-20% larger than the maximum width of the left atrial
appendage measured by TEE). This finding supports that late
device-related complications can occur despite appropriate
antithrombotic therapy and appropriate device sizing, and questions
whether surveillance imaging up to 1 year is sufficient. Staubach et al
showed that new DRT continues to be detected on longer term follow-up
(>12 months) and a sub-study of the PROTECT-AF trial also
showed an increase in DRT at 5 months and 12 months, although early
anticoagulation was not rigorously documented.8,12Delayed DRT may be related to incomplete endothelization which has been
discovered after removal of device and in postmortem
reports.13,14 Further investigation is needed to
determine patients who are at higher risk for incomplete endothelization
of the device and thrombus formation and therefore would warrant
extended surveillance imaging and anticoagulation therapy.
There is a wide range in the incidence of PDL, reported between 15-40%,
which varies based upon the cutoff used to determine a clinically
significant leak.6 Delayed endothelization and device
undersizing have been proposed as mechanisms for the occurrence of
PDL.15 The cutoffs used to discriminate significant
leaks in the literature, usually >3mm or >5mm,
have been selected arbitrarily and are not based upon clear data and the
clinical importance of a persistent leak remains controversial. Our
study showed a decrease in the incidence of PDL over 1 year follow-up,
however there were 5 patients with new PDL detected at 1 year that were
not seen at 45 days. The PROTECT AF study showed that over 30% of
patients had major PDL (defined as >3mm) at 45 days and 1
year and presence of PDL was not associated with an increase in
thromboembolic events, however interpretation of this is limited by the
low event rate.16 A more recent study showed that PDL,
irrespective of size, was associated with a higher incidence of TIA or
stroke, supporting the use of the lower cutoff of 3mm for our
study.7 Given the unclear consequence of persistent
leaks and the availability of percutaneous PDL closure, further
investigation of the implication of PDL is needed as well as
determination of a significant cutoff.
Limitations
Several limitations to this study merit consideration. This is a
retrospective single but high-volume center study, and our results may
not be universally applicable, especially in centers with lower volumes
of LAAO. Long-term follow-up clinical data was missing for many
patients, therefore we cannot comment on clinical outcomes or TEE data
beyond one year. We were unable to correlate international normalized
ratio values with the presence or absence of DRT for patients taking
warfarin. Antithrombotic therapy at 45 days and 1 year were obtained
through the NCDR LAAO Registry, however adherence to therapy between
these dates cannot be confirmed. Although all DRT at 45 days was treated
with continued anticoagulation and all resolved by 1 year, the exact
duration of treatment is unknown. The findings of this study are
relevant only to the Watchman device and may not be applicable to other
LAAO devices including the newer Watchman FLX, therefore the rates of
device-related complications in this study may not apply to other
devices. Cardiac computed tomography, which has been shown to be a
feasible alternative to TEE for detecting device-related complications
after Watchman, was not used in this study.15,17Finally, we did not have outcomes data such as thrombo-embolic event
rates.
Conclusion
Our study showed that surveillance imaging identified several
device-related complications including DRT and PDL at 45 days and 1 year
after Watchman placement, despite the appropriate use of antithrombotic
therapy. The incidence of DRT was slightly higher at 1 year compared to
45 days and all DRT at 1 year were new cases, further highlighting the
need for TEE surveillance at these two timepoints and potentially a need
for even longer follow-up to identify delayed complications. Limited by
sample size, we could not identify patients at high or low risk in whom
TEE would definitely be needed or could be safely deferred,
respectively. Further investigation is warranted to determine the
optimal timing and duration of surveillance imaging after Watchman
placement and further elucidate the clinical consequences and ideal
treatment of device-related complications.
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