What are the characteristics of a cardiac cough?

Night time likely. It is mostly night time associated with shortness of breath lying down in bede, pt feels better sitting upright.
Difficult to say. A cough worse at night when lying flat in a pt with known heart failure is the classic description . But when a pt has COPD or other lung problems it more difficult to tell. Also pts on acei pills will be prone to cough. A full h&p is usually needed along with a cxr and labs.