VO2 during peak exhaustive exercise (left panel) and during submaximal exercise at the ventilatory anaerobic threshold (right panel) in age-matched normal subjects (NO), elderly patients who have heart failure caused by systolic dysfunction (SD), and elderly patients who have heart failure with normal systolic function, that is, presumed diastolic dysfunction (DD). Exercise capacity is severely reduced in patients who have DHF compared with normal controls (P<.001), to a degree similar to the reduction in patients who have SHF. Overall, peak exercise VO2 was 33% lower in the women than in the men (not shown). (Data from Kitzman DW, Little WC, Brubaker PH, et al. Pathophysiological characterization of isolated diastolic heart failure in comparison to systolic heart failure. JAMA 2002;288(17):2144-50.)