4. Discussion
The key finding of this study is that both manual and newer
semi-automated 3DTEE measurements of the aortic annulus correlate well
with MSCT. It had been previously reported that 3D TEE sizing of the
aortic annulus was unable to accurately predict the implant size of the
TAVR device when compared with MSCT [30-34]. Thus, MSCT has become
the gold standard imaging modality for TAVR planning [29]. However,
our findings plus other recent studies suggest that newer and improved
3D TEE technology is comparable to MSCT [35,36,38]. In the era of
significant improvements in both imaging modalities (MSCT and 3D TEE), a
recent systematic review and meta-analysis suggested that in pre-TAVR
planning, 3D TEE is comparable to MSCT [39]. Indeed with rapidly
increasing indications for TAVR, there’s a crucial role for 3D TEE in
those patients that cannot undergo MSCT. As such, we wish to emphasise
that the 3D TEE should not be forgotten as it is an excellent
alternative for annular sizing pre-TAVR. The main concern for TEE was
annulus under sizing (compared to MSCT) resulting in PVAR. This was not
the case in our cohort, particularly for semi-automated 3D TEE
measurements. Indeed, when using the semi-automated technique for
annulus area (the most robust measurement for sizing), the prosthesis
sizing was different in only one patient which suggests that there is no
real clinical difference between the two modalities. Moreover, in this
single case the difference in measurements was only marginal and the 3D
TEE actually predicted a larger prosthesis size. The inter-observer
variability was very low when using the semi-automated 3D TEE method
indicating that automating some of the measurement reduced the
difference between readers. Our study provides great confidence in not
only choosing 3D TEE when MSCT is contra-indicated but suggests that it
is an excellent alternative regardless. Therefore, with better 3D TEE
analysis packages specifically designed for the aortic annulus now
available on the market which often use identical techniques to MSCT
measurement methods, the mantra that MSCT is the gold standard needs to
be revisited by further comparative studies [32,34]. Whether using
3D TEE alone in these cases will result in similar procedural outcomes
such as PVAR compared to MSCT is not well known at this stage, but the
fact that these two different imaging modalities chose the same
prosthesis size in nearly all cases in our cohort suggests that the
clinical outcomes would likely be comparable.