Generally 10% neutral buffered formalin.
See also: General notes on fixation
Heart specimens are generally not inked.
Basic microscopic screening
Generally check for signs of myocardial infarction. Further information: Autopsy of myocardial infarction
Myocardial lipofuscin reflects normal ageing rather than any cardiac pathology, and does not need mentioning in the elderly.
Ruptured intercalated discs. Further information: Ruptured intercalated discs
Fibrosis. Further information: Myocardial fibrosis
Rectangular "Boxcar" nuclei: Look for myocardial hypertrophy, especially when enlarged. Otherwise, ruptured intercalated discs can cause square shaped nuclei.