Pre-dilation should be performed in case of very tight lesions (pre-occlusive stenosis) associated with heavy calcified lesions that cannot be crossed by the device.
Lesion dilation before stenting was strongly recommended in the first part of CAS experience when large-profile devices were used and several works documented that more debris could be liberated from the lesion site when pre-dilation was not performed.
But with the introduction of very-low monorail devices, pre-dilation has begun to be avoided reducing complications mainly when dilation is performed before introduction of any cerebral protection system.
In fact pre-dilation increases not only the risk of atheroembolism but also the possibility of vessel wall dissection and trauma.
Pre-dilation must be avoided in the presence of unstable plaque or fresh thrombus for the higher chance of plaque debris and consequent neurological complications.
If the lesion is preocclusive and impenetrable to even low-profile devices, it is preferable to gradually step up the balloon size to minimize plaque disruption and distal embolization.
In these situations pre-dilation should be performed with a 2.0 mm balloon followed by a second inflation of a 2.5 to 3.5 mm balloon.
To reduce the risk of plaque disruption and wall damages the length of the balloon is suggested to be no longer than 2 cm.
No injection of Atropine is needed when pre-dilation is performed with a very small balloon because no carotid sinus reflex can occur.
When the cerebral protection is able to go through the lesion but the stent device isn’t pre-dilation can be performed more safely because the cerebral protection minimizes the risk of cerebral ischemic complications.
In the presence of a severe lesion we suggest trying to go through the lesion for 2-3 times with a 0.014" guidewire of the protection device first and then, after failure, performing pre-dilation.
If the 0.014" guidewire of the protection device succeeds in going through the lesion but the stent device doesn’t, pre-dilation is highly recommended.

Technical Note:
Dilation should always be performed using small balloons because the final target of the procedure is to create a passage fit for low profile devices.
Consequently very low profile balloons on a 0.014" platform, coronary type, are considered the most eligible.