Simplify the following text for a Grade 8 native English-speaking person.
Original: Heart failure ( HF ) is generally defined as inability of the heart to supply sufficient blood flow to meet the body 's needs . It has various diagnostic criteria , and the term heart failure is often incorrectly used to describe other cardiac-related illnesses , such as myocardial infarction ( heart attack ) or cardiac arrest .
Simplified: Heart failure is different from cardiac arrest , because the heart is still working .