Thanks for your question on Health Care Magic.
I can understand your brother in law 's situation and problem.
Since he is known case of
valvular heart disease and
bypass surgery, possibility of heart related diseases like
arrhythmia is more.
Arrhythmia can cause flushed tingling sensations in chest.
He is also having low blood pressure while symptoms. This is also favouring arrhythmia more.
So better to get done ecg, 2d echo and Holter monitoring (24 hour continuous monitoring) to rule out arrhythmia.
If all these are normal than no need to worry arrhythmia.
Sometimes
gastritis can cause similar symptoms. So ask him to take
proton pump inhibitors.
Don't worry, he will be alright, but better to first rule out arrhythmia.
Hope I have solved your query.
Wishing good health to him. Thanks.