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.