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Page 6 of 10 Sticchi et al. Vessel Plus 2018;2:23 I http://dx.doi.org/10.20517/2574-1209.2018.47

an easy insertion of the oversized TAVI sheath. Furthermore, retroperitoneal anatomical structures guaran-
tee a low risk of bleeding that may be due primarily to the arterio-venous shunt, which is repaired with an
[33]
occluder device at the end of the procedure .
The main challenge of this approach is the making of the cava-aorta connection through the intersection of
the two vessel walls at the abdominal level. This can require multiple attempts by less experienced operators
to achieve the entry in aorta, the use of haemostatic techniques, transfusions and the treating of leaks due to
ineffective repairs. However, the learning curve appears to be short and procedural times are similar to those
[34]
of femoral access .

Considering the importance of the vascular roadmap to reach the aortic annulus for the valve implantation,
the evaluation of the pre-procedure CT study becomes fundamental for the assessment of the calcifications,
the diameters and the tortuosity of the vessels. Specifically, the crossing of the cava-aorta requires careful
evaluation of the calcification and of secondary branches in order to allow a successful closure of the iatro-
genic fistula with an occluder device. Porcelain aorta, previous abdominal endograft and other abnormalities
of the aortic wall, represent a contraindication to this access, like an iliac severe tortuosity for the femoral
[35]
access .
So, this approach is a valid option only in patients with a precise vascular anatomy and the for its hidden
tricks it should be performed by skilled operators in experienced centers. Finally, it needs further studies,
[36]
especially about the safety of the method .

COMPARISON AMONG ACCESS SITE
The safety and performance of the TF approach, that have been achieved thanks to the extensive TAVI expe-
rience, are the main model of comparison for other access options. The TF approach is to be considered the
only completely percutaneous access with the use of the femoral crossover technique and vascular closure
devices. Alternative routes are subject to the inability to perform the procedure through the femoral access
and they are identified as independent predictors of overall and cardiovascular mortality at 5 years in the
[37]
real-world population .
TA and transubclavian access are the most used routes in presence of contraindications to the femoral ap-
proach and they both show high rates of procedural success. The only difference between them and the TF,
although it is not statistically significant, is represented by a greater incidence of potentially fatal bleeding for
[38]
the trans-apical approach .

Studies reveal a reduction in vascular complication rate using transapical and trans-subclavian access com-
pared to a fully percutaneous femoral access. While this is easily understood for the transapical access due to
[39]
its inherent features, data for the trans-subclavian are difficult to explain .

A comparison between TF versus transubclavian access produces no considerable differences in 30 days
mortality, stroke and new pacemaker implantation. Similarly to the transubclavian access, the trans-axillary
compared to the TF approach shows no relevant differences in 30 days mortality but it needs general anaes-
[40]
thesia more frequently and leads to a greater tendency of vascular complications .

On the other hand, the trans-apical approach is a more invasive procedure and involves a higher rate of sur-
gical conversion, longer hospitalization, a higher rate of renal failure and higher mortality rates than the TF
[41]
route . Furthermore, no statistically significant differences are reported in stroke incidence and new pace-
maker implantation using the trans-apical compare to the femoral access [39-41] .