What Causes Sharp Pain In Shoulder Radiating To Armpit?

My husband, has been experiencing what he refers to as an electrical shock in his left armpit through shoulders. It has happened 2 times in the last 3 hours. History, he had a heart attack in 2008, quadruple bypass. Family history of heart issues. He had mentioned several times over the last week that when he reaches for things he gets a sharp (electrical shock) pain in his wrist. He is not having chest pain, and was resting when the pain occurred and it only lasted a few seconds. Any ideas?