Antegrade flow in the vertebral arteries refers to the flow of freshly oxygenated blood away from the heart toward the brain. The blood is channeled from the heart through the subclavian arteries before reaching the vertebral arteries.
The vertebral arteries traverse the spine by entering at the sixth cervical vertebrae and exiting through the first cervical vertebrae at the top of the neck. From there, the vertebral arteries enter the skull via the foramen magnum, a hole at the base of the skull. Inside the skull, the two vertebral arteries join to form the basilar artery near the base of the brain stem. When blood flows in a reverse direction through the vertebral arteries, this causes a medical condition called subclavian steal syndrome.