Clairsentience is a term given to psychic or spiritual feeling, the gut instinct and is probably one the of most common and natural types of skills particularly common in women and children, this is a natural thing especially between mother and child. The term 'gut feeling' is quite appropriate with clairsentience as it deals with the solar plexus chakra.
As children we are all quite open intuitively and emotionally, but as we grow older these senses kind of shut down, this also applies to "imaginary friends" we have as children, but more often than not, these imaginary friends are actually spirit people. Adults tend to dismiss this and say to the child "Don't be so silly" "There's no one there" this in turn closes the ability to see and feel spirit.
When using clairsentience we will feel people emotions and pains, the same applies to spirit people when we are in tune on a clairsentient level we will very often feel how the spirit person passed over, if the person passed with a heart condition then we may feel this in our chest area, we may also feel other things from the spirit person, joy, happiness or any other feelings that may be there to aid them in identify themselves.
You should always rule our any medical conditions before assuming anything of psychic or spiritual nature.