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Exercise intolerance in heart failure with preserved ejection fraction: what does the heart have to do with it?

Heart failure (HF) occurs when the cardiac output is unable to meet the body’s needs without an elevated filling pressure.1,2 Thus, exercise intolerance is an important symptomatic manifestation of HF, including patients with HF and a preserved ejection fraction (HFpEF).3

Articles see p 278 and p 286 

Two similar studies in this issue of Circulation: Heart Failure have reached different conclusions on the importance of cardiac dysfunction in producing exercise intolerance in HFpEF.4,5 Both groups performed upright cardiopulmonary exercise testing with hemodynamic monitoring in patients with preserved ejection fraction, elevated pulmonary capillary wedge pressure (PCW), and exercise intolerance. Santos et al4 found that the major contributor to exercise disability was a limitation of cardiac output, indicating a cardiac cause. This finding is consistent with a similar study by Abudiab et al.1 In contrast, Dhakal et al5 found that a peripheral limitation was the most important cause of reduced aerobic capacity, whereas impaired cardiac output had less impact. This finding is consistent with 2 other studies that indirectly estimated oxygen extraction.6,7 The goal of this editorial was to put these studies in perspective and explore what they tell us about HFpEF.

The delivery of oxygen to contracting muscles is essential to perform aerobic exercise. Optimum oxygen delivery requires oxygenation of the blood in the lungs, normal oxygen carrying capacity of the blood, adequate cardiac output that is appropriately distributed to match regional demands, and adequate tissue extraction of oxygen from the blood. Normal adults can increase oxygen consumption (Vo2) >6-fold during exercise by: (1) increasing cardiac output because of a faster heart rate and enhanced stroke volume, and (2) augmenting oxygen extraction producing a fall in mixed venous oxygen content, thereby increasing the difference between arterial …