Technical success in CAS depends almost entirely on the ability to gain access to the common carotid artery through a long introducer sheath or a guiding catheter.
Procedural failure is generally caused by the inability to advance an introducer or a guiding catheter into the common carotid artery (CCA) sometimes for a difficult take-off from the brachiocephalic trunk or from the aortic arch, sometimes for a significant kinking or coiling of the CCA itself.
Baseline images of the aortic arch and of the origin of the carotid arteries obtained with digital subtraction angiography (DSA), CT-angiography (CTA) or Magnetic Resonance-angiography (MRA) are very helpful to select the best approach.
CCA catheterization can be performed using different techniques:
Direct approach, Telescopic approach and Telescopic approach with coaxial technique.

Direct Approach: movie 1

A guiding catheter (6-8 Fr) is advanced on a standard hydrophilic guide-wire (0.035"-180cm, angled tip) into the aortic arch.
The guiding catheter is then rotated into the aortic arch to directly engage the CCA.
Once the hydrophilic guide-wire is advanced into the CCA the guiding catheter is pushed over the wire until the desired position, 2-3 cm below the carotid bifurcation, is reached. Fig.1
If more support is required to advance the guiding catheter, because of a difficult take-off or a severe kinking of the CCA, the wire must be gently advanced into the external carotid artery (ECA).
All these manoeuvres must be performed under fluoroscopy guidance with a road-map technique in order to avoid the passage of the wire through the carotid lesion.
Moreover the guiding catheter allows a continuous contrast media injection to better visualize the CCA origin and the carotid bifurcation giving more information to decide where the wire and the guiding catheter itself should be directed.
In case of a very tortuous anatomy an extra-wire can be added (buddy wire) to give more support and to facilitate the advancement of the guiding catheter.
We generally suggest combining a standard hydrophilic wire with a stiff-hydrophilic one.
To facilitate the CCA catheterization different shapes of the guiding catheter should be selected on the basis of the patient’s anatomy :

- Right CCA: Multipurpose (MPA), Hockey-stick (H), Amplatz Left 1 (AL-1)
- Left CCA: Amplatz Right 1 (AR-1), Femoral Curve Right (FCR 3.5), Hockey-stick (H)
- Left CCA from the Innominate trunk: Amplatz-Right (AR-1), Amplatz Left (AL-1), Femoral Curve Right (FCR 3.5)

To perform a direct approach to the CCA specific guiding catheters must be chosen with a very soft tip to avoid arterial wall damages and with a stiffer distal portion to give a better support and a better torquability and pushability.
Once the guiding catheter is placed in the correct position, 2-3 cm below the carotid bifurcation, the hydrophilic guide-wire can be removed and the procedure completed in the standard fashion.

Telescopic Approach: movie 2

A diagnostic catheter (4-5Fr / 100cm) is introduced into the aortic arch to engage, together with a hydrophilic 0.035" guide-wire (180cm - angled tip) the selected CCA.
Catheters with different shapes should be selected on the basis of the anatomical characteristics of the aortic arch and of the carotid arteries origin:

- Right CCA: Sidewinder-Sim 1, Headhunter-H 1, Multipurpose-MPA
- Left CCA: Sidewinder-Sim1, Vertebral-Ver, Berenstein-Bern
- Left CCA arising from Right side: Sidewinder-Sim1, Newton-HN4, Bentson-JB2

Once the CCA is catheterized, the diagnostic catheter is advanced over the hydrophilic guide-wire into the external carotid artery.
This step of the procedure must be performed using a road-map technique in order to facilitate the passage of the wire into the ECA avoiding any contact with the lesion of the internal carotid artery (ICA) which may lead to possible dislocation of the material.
When the catheter is in its correct position within the ECA, the hydrophilic guide-wire is retracted and a long (260cm), high support, floppy tip, 0.035" wire (Amplatz super-stiff wire) is positioned in the ECA through the diagnostic catheter.
After removing the diagnostic catheter a long introducer (6-7Fr / 90cm) with its inner dilator is advanced into the CCA, 2-3 cm below the carotid bifurcation. Fig.2
In case of a very tortuous anatomy, partial retention of the wire and of the dilator can be helpful to cross severe angled curves.

Telescopic Approach - Coaxial Technique:

Telescopic approach can be also performed using a coaxial technique. movie 3
A 4-5 Fr diagnostic catheter (>110 cm in length) is preloaded into a long introducer (6-7Fr / 90cm) or a guiding catheter (6-8Fr / 90-100cm).
All the coaxial system is advanced into the aortic arch using a hydrophilic guide-wire (0.035"/260cm, angled tip).
The CCA is engaged with the diagnostic catheter and the hydrophilic guide-wire. The diagnostic catheter is introduced into the CCA below the carotid bifurcation.
Then either the guiding catheter or the long introducer is advanced over the wire and the diagnostic catheter. Fig.3
Only in the presence of high tortuosity an extra-support wire is recommended.

All different techniques performed to engage the CCA present advantages and disadvantages.
Any method, however, must be selected on the basis of the anatomical configuration of the patient and on the basis of the practitioner’s personal experience. Fig. 4-5-6

References