I have 69% blockage in the left carotid artery. I also have dizzy fainting spells. What should I do?

Be evaluated. A 69% carotid artery blockage on one side isn't enough to cause dizziness/ fainting spells. Is it low blood pressure, anemia, a middle ear problem? It's best to have your internist work through the possible causes. With regard to your cerebral circulation, it would be helpful to know how your vertebral arteries look. A simple ultrasound can evaluate these arteries which supply the balance center.
Cta. Need cta of your head and neck to evaluate all the vessels in your head and neck. This will help determine treatment. Also check to make sure no medications could be causing the symptoms.