What Causes Radiating Chest Pain With Shortness Of Breath?

My husband is 33 yrs old. About two weeks ago he was having chest pain radiating down his left arm and difficulty breathing. When I listened to his heart the rhythm was irregular. Today he had an ekg and it showed sinus rhythm with significant sinus arrhythmia and left axis deviation. Coulit be that he had a heart attack two weeks ago? If not what?