What Causes Right Sided Radiating Pain From Shoulder To Neck?

My husband has been having some throbbing pain in the left side of his neck, from shoulder to upper neck. The pain is a 6 on scale from 1-10. He is on 3 different blood pressure medicines. Could it be his artery in the neck. Also, the last time he saw his doctor his potassium level was low. She told him to eat more fruits.