What Do This Ultrasound Test Result Indicate?

The report of my ultrasound says my left vertebra artery is fully clogged. ( "LT VERT is fully occluded"),Can you comment: do we have two of these artery one left and one right, can we survive only with one? I am 66 years old ; is it worth it to consider a surgery to unclog it , assuming there is such a surgery?
Sam