The Role of CT-scan
Over the years, several discussions about the use of CT-scan for LAA
occluder device sizing have been raised by investigators, leading to
non-homogeneous conclusions. The main reason for this disappointing
position is likely to relate to the scarcity of robust data, since there
is still difference among institutions with regards how to perform
measurement of the devices. In several institutions, the pre-procedural
device sizing is guaranteed by TEE carried out at the same time of
thrombus evaluation in LAA. Therefore, even for the workflow’s sake,
CT-scan is no strictly required and the procedure itself relies on
sizing obtained by fluoroscopy and TEE in real time during the
procedure.
One could raise the question whether pre-procedural CT-scan is critical
for identifying the right device sizing and, thus if it should become
the standard approach for LAA closure. Based on the preliminary data
offered by Dallan and co-workers, it seems that the novel TruPlan
software accurately provides the size of device and it might also
improve the patient’s workflow in the lab. Moreover, they did not
observe device embolization, nor strokes or any other major
complications. The CT sizing strategy adopted by the authors was
associated with only 1.04 devices used per patient. Furthermore, this
approach yielded a 99% procedural success and 99% closure rate at
45-day follow up which compares with previous clinical outcome reported
with TEE (7,8). In other words, the CT sizing through the TruPlan
software does not negatively affect the outcome of Watchman Flex device.
Actually, based on these results, very comparable to the current use of
intraprocedural TEE and/or ICE, the operators have their own choices of
how to perform LAAO intervention. Then, which is the real novelty for
the physicians provided by the TruPlan software? First, the methodology
of LAA measurements based on an area-derived diameter as opposed to the
maximum diameter currently offered by CT technique provides a more
adequate device sizing thus, reducing the likelihood of device
over-compression. In fact, sizing and compression estimates are derived
automatically, and device selection can be chosen based on area-derived
diameter. Moreover, it seems even more crucial the role of the TruPlan
software in selecting the most adequate device when two device sizes fit
within the recommended 10-30% compression range. Under these
circumstances, the algorithm would select a larger device at higher
compression if accommodated by appendage depth. Once selected, TruPlanTM
digitally superimposes the device onto the CT image of the appendage.
The device overlay feature is certainly a key element in
decision-making, to assess adequacy of fit. Then, the device can be
virtually repositioned in the appendage to predict how appendage tissue
might interact with the device upon implant. Interestingly, the program
simulates device shape at any predicted compression, forecasting how the
device will appear fluoroscopically in the appendage.