Patients with chronic heart failure can be divided into 2 broad categories: systolic heart failure and diastolic heart failure. There are significant differences in demographics, prognosis, left ventricular structure, as well as systolic and diastolic function between these 2 groups of patients. The purpose of this presentation is to define the terminology used to describe these 2 broad categories of heart failure and to characterize the functional measurements that constitute their pathophysiological mechanisms.