Abstract: The present invention provides a method of evaluating pathological conditions of heart failure based on a new mechanism of action of heart failure, a method of evaluating a candidate compound for a heart failure treatment drug using the mechanism of action, and a pharmaceutical composition for treating or preventing heart failure using the mechanism of action. That is, the present invention provides a method of evaluating pathological conditions of heart failure including measuring an amount of succinyl-CoA in cardiomyocytes collected from a test animal, a respiratory capacity of mitochondrial complex II in peripheral blood mononuclear cells collected from the test animal or an amount of reactive oxygen species released from peripheral blood mononuclear cells collected from the test animal; and evaluating the onset of heart failure of the test animal or the severity of heart failure based on the obtained measurement values.