Dear friend, welcome and thanks for entrusting your query here at HCM !
you son seems to have a significant heart disorder with a murmur and a possible heart failure
and consequent frothing at mouth.
Is it rusty red bubbly froth woth breathlessness?
Does he have swelling over ankles?
Does he turn bluish at tips of fingers/ tongue?
This needs urgent attention and evaluation by 2D echo-doppler and may need admission.
Take second opinion
if one is not showing interest.
The condition may be fatal.
I hope you are fully satisfied with the guidance I gave.
I would be glad to answer any further queries.
Thank you and Good luck !