Some causes related to cardiovascular disease:  While fever is an uncommon cardiac symptom, increased body temperature can be seen with a myocardial infarction, an infection involving the heart or heart valves (a condition called endocarditis), or with inflammatory diseases involving the heart or pericardium (such as pericarditis). 

Some causes related to other disorders: Hundreds of medical illnesses can cause fever.  Most fever is not related to heart disease

Significance: Fever accompanied by any other potentially cardiac symptoms need to be evaluated by a physician.