Type II endoleak is the most commonly encountered and also the most controversial type of endoleak.
Even though at low-flow,
type II endoleaks may prevent thrombosis of the aortic sac and create a potential risk of continued aneurysm expansion and potential rupture.
Type II endoleaks account for about 40% of all endoleaks and are reported in 10-25% of EVAR cases at 30 days (4,9).
The best indicator of hemodynamic significance of a type II endoleak is the associated change in the aneurysm sac: if the sac increases in size,
higher pressure and a relatively higher risk of long-term rupture are implied.
If the sac is stable or decreasing in size,
the risk is likely to be less.
Many clinicians assume a “wait and see” approach with regular follow-up when there is no expansion of the aneurysm size,
as up to 40% of type II endoleaks will eventually spontaneously thrombose (10,11,12).
A more aggressive approach may be warranted in patients with persistent type II endoleak that has not resolved spontaneously within 6
months even in the absence of aneurysm enlargement.
Authors indeed assume that collateral vessels can continue to transmit arterial pressure to the aneurysm sac and increase the risk of rupture,
hence type II endoleaks should be treated if persisting after 6 months (13).
The
strategy of pre-emptively occluding potential sources of collateral inflow has been widely accepted for some branch vessels,
such as the hypogastric artery,
but remains controversial for patent inferior mesenteric artery and lumbar arteries (14,15). The most common technique of type II endoleak management is TAEE of the branch vessels with embolization using coils,
glue,
or thrombin. However,
the unsuccessful embolization depended on the catheterization and complete embolization failure of the feeding arteries at the ostium of the aneurysm sac or to a partial embolization of the afferent branches,
therefore this technique requires advanced endovascular skills and often is not feasible in all patients because of anatomic limitations. During follow-up,
failure and recurrences have been reported in up to 80% of cases since endoleaks often appear again because of multiple communicating vessels or persistent flow
through the coils.
(7).
In such cases,
the TLEE under fluoroscopic or CT guidance can be attempted as primary treatment modality (7,16-19,
26-29).
This technique,
first described by Baum et al.
(7),
may be used as a primary treatment or after failure of transarterial approach.
Baum et al.
showed that translumbar embolization was durable with a success rate of > 90% after 8 months.
A translumbar transcaval approach with CT guidance for right-sided aneurysms (20) and a transabdominal approach with ultrasonographic guidance(16) have also been reported as alternatives to translumbar direct puncture of the aneurysm sac (21,22).
TCEE represents an endovascular technique which offers several advantages.
The entire procedure is performed in the angiography suite in the supine position,
under fluoroscopic control; as a result,
patient compliance during the treatment is improved.
The inferior vena cava is only punctured in one site instead of in two different points,
as occurs with the Trans Lumbar approach (18,20).
Therefore,
a lower risk of retroperitoneal hemorrhage is expected.
An accurate pre-procedural CTA evaluation and the eventual presence of aortic wall calcifications are usually very usefull to the correct orientation of the needle during sac puncture.
Thereafter,
the placement of the catheter directly inside the aneurysm sac permits intrasac pressure monitoring.
The embolization results are followed with usual angiographic
controls. The percutaneous venous access can be achieve either with a transfemoral or transjugular puncture.
Currently,
we prefer transfemoral percutaneous access because,
in our opinion,
it allows a better orientation of the curved needle/sheath system to the site of puncture.
As a result,
the embolization is performed in conditions of safety,
under complete sterility,
and enables a choice of materials.
TCEE was first described by Mansueto et all.
using metal coils and/or thrombin injection under intrasac pressure monitoring (23).
We believe that the real-time visualization of the distribution of the embolic agent during its injection is essential for determining its optimal required quantity.
Thereby,
in our series,
we preferred the use of Glubran 2 acrylic glue mixed with Lipiodol instead of thrombin alone.
Lipiodol enabled the fluoroscopic visualization of the glue.
Moreover,
we preferred use platinum coil instead metallic coils to reduce attenuation artifacts on follow up imaging studies.
The persistence of glue mixed with Lipiodol or of contrast material,
and the absence of dynamic flow within the aneurysm sac indicated the complete resolution of the endoleak. The demonstration of stable contrast inside the sac on unenhanced CT scan at 24 hours is considered as technical success as well as proof of immediate clinical success. Intraprocedural evidence of technical success can be obtained by intrasac pressure monitoring by placing a 5F catheter directly inside the aneurysm sac.
Few reports have been published about the relationship between intrasac pressure and endoleak changes (24,25). The disappearance of the pressure waveforms and a reduction in intrasac pressure can be considered as a marker of successful embolization. We demonstrated that in patients successfully treated,
the disappearance of systolic-diastolic waveforms or the reduction of intrasac pressure had been observed during TCEE,
obtaining a stable or decrease of sac dimensions and an excellent clinical success rate.
Nevertheless, we have to keep in mind that measurement may be compromised by several pitfalls.
The disappearance of the pressure waveform can be mainly due to the exclusion of the endoleak by blood flow but also by contact of the catheter tip with the aneurysmal wall,
even in instances where there is persistent blood flow or the presence of glue/thrombin inside the catheter.
To reduce the impact of these two pitfalls on the reliability of the procedure,
we rotated the catheter tip to record the presence of residual blood flow and we washed the catheter with saline after every thrombin injection. The major limitation to TCEE is that it can be performed only in cases in which the aneurysm sac is adherent to the inferior vena cava and there is sufficient space between the aneurysm’s wall and the endograft,
condition present in most of the abdominal aortic aneurysms.
This information is obtained with CTA which is thereby mandatory for an accurate pre-procedural planning.
In case of no CT evidence of a tight adhesion between cava and aortic wall,
we think that direct translumbar/transcaval puncture of the aneurysm sac should be considered as the first approach proposed for embolization of type II endoleaks. The only two minor complications we reported in our series were thrombophlebitis at the site of femoral percutaneous venous access while a major complication,
as aneurysm rupture,
was reported as clinical result of uTCEE during the follow-up period.
Other possible complications related to TCEE are retroperitoneal hemorrhage and cavalaortic fistulas.
If there is a tight adhesion between the caval walls and the aneurysm sac,
the development of a retroperitoneal hemorrhage should rarely occur.
Moreover,
in our opinion,
we managed to avoid hemorrhage complication thanks to the angle modification of the needle Colapinto tip that allowed an orthogonal approach.
It is also worth noticing that TCEE requires a thin needle cannula and a 5F catheter,
which are quite small in caliber and causing only small holes in the caval walls. The caval-aortic fistulas represents a rare complication likely due to the significant decrease of the intrasac blood pressure after the embolization. A cavography at the end of the procedure,
as well as CT scan at 24 hours after treatment can check for both of these complications and treatment can be undertaken by placement of coils or a device like those to close inter-atrial cardiac shunts. The current study has certain limitations.
The small number of treated patients cannot support a certain conclusion of success or complication rates. We observed no significant differences of technical success between uTCEE and sTCEE.
The selective procedure requires greater technical skill and a quite longer procedural time; it showed clinical success of 100% compared to the unselective that showed a recurrence rate of 44,4% in our cases.
We believe it is necessary to embolize all visible afferents to prevent new supplies to the sac.
In addition,
one patient treated with uTCEE showed rupture of the aneurism probably because the afferent vessels continued to transmit arterial pression to the sac,
without visible endoleak.
Our aim was to consider if the TCEE as at least as feasible and successful as other approaches in common clinical practice.
CONCLUSION
Currently,
no treatment is considered the gold standard for type II endoleak management; as a result,
a tailored treatment should be preferred.
Different approaches have been proposed for embolization of type II endoleaks.
We evaluated sTCEE as primary therapeutic option and it appears to be a promising and feasible technique for thrombosis of type II endoleaks. It does not require high operator skills and can be performed by almost all endovascular specialists in most clinical contexts using a simple C-arch. According to the results of our study,
TCEE technical and clinical success rates are comparable with other treatment strategies,
and it can be proposed as first line therapy in presence of type II endoleak caused by one or multiple feeding vessels.