Heart problems - affect about 1% of patients. This may present as a heart attack, problems with the heart rhythm or possibly death.

Stroke - this can affect approximately 2% of patients. It can be minor (causing minimal problems) or it can be major (causing significant long-term problems with mobility and mental function). Major strokes may lead to death.

Death - this can occur for various reasons as stated above and can affect 1 - 2 % of patients.

Blood pressure problems - because the area of the carotid arteries being operated upon is involved with blood pressure regulation, problems are not uncommon. These can occur during or after the operation and may include the blood pressure becoming too high or too low. If the pressure becomes too high, there is a risk of bleeding into the brain.

Damage to cranial nerves - this is not uncommon and have been noted to some degree in up to 50% of cases. Most are temporary with resolution of symptoms in a few months. The nerves that can be affected are the ones that supply the muscles of the lower face, the tongue, the gullet and the vocal cords. 

Damage to sensory nerves - this happens in almost all cases. Nerves that supply the skin of the neck with sensation are cut during the initial incision.

Bleeding - this is a fairly dramatic complication that causes the accumulation of blood deep in the wound. This can occur despite the presence of a drain. It causes pressure on the windpipe such that you would have difficulty breathing. An emergency operation to drain the blood is necessary.

Wound infection - this is not very common, most are superficial and settle with antibiotics. Infection of synthetic patches is very uncommon (<1%) but is a more significant problem as the infected material may need removal.

Deep vein thrombosis - is a risk with any operation.

Recurrent severe narrowing - enough to cause symptoms is uncommon (less than 3% per year after surgery).