1
general::
Grieving, very disappointed, dejected, as in We were sick at heart when we learned of her predicament. This idiom, which transfers heart disease to unhappiness, was first recorded in 1581.
American Heritage Idioms
2
general::
Phrase(s): *sick at heart
Fig. distressed and depressed. (*Typically: be ~; become ~; make someone ~.) • I became sick at heart just looking at all the homeless children.
McGrawhill's American Idioms And Phrasal Verbs