It also sounds a lot like a panic attack, which can be caused by stress... but also influenced by things like parasites and heavy metals.....
get his heart checked.... but in the meantime..if he is interested, bowel, parasite and Liver Cleansing will really really help......( I used to have panic attacks) After a month or two of parasite cleansing I only rarely have had a very mild attck...compaired to the 3 a day I used to have....
You also might want to check out if it is environmental... like mold in the house..or other problems like that..if you both have had these problems....
Something that will help right away would be to pick up some Bach's rescue remedy at a health food store..that will help take the panic and fear out of the situation when it happens.... (use four drops right in the mouth when the fear(or palpitations start)......