What could cause a heart

My brother,who is 47 yrs old and has never had any heart problems before now..has been feeling a heart "fluttering" in his chest for 3 days now.He said the only time he does not feel it is when he is sleeping or working hard(he owns a roofing company).He has been under some stress lately because his wife as been diagnosed with graves AND lupus disease,so I'm sure that is not helping the situation.I told him he should see a doctor A.S.A.P..not to screw around and put it off.Please give me some info so I can put a fire under his butt about seeing a doctor.Thank you!!