Misunderstood and Overrated (Changing the Paradigm in Categorizing Heart Failure)
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The long-standing emphasis on ejection fraction (EF) is misguided. EF is erroneously assumed to be a measure of myocardial contractility. Of greater concern is the widespread classification of patients with heart failure (HF) based on whether EF is preserved (HFpEF) or reduced (HFrEF). In fact, EF does not provide any specific information on causation or underlying mechanisms. We believe that a revision or abandonment of this nomenclature is warranted, and categorization of patients with HF should more strongly emphasize underlying pathophysiology
What EF Represents
EF is a characterization of ventricular ejection: the stroke volume (SV) expressed as a fraction of end-diastolic volume (EDV). Knowledge of EDV is essential to translate SV expressed as a percentage (EF) into absolute SV, a quantity of more physiological and clinical significance, hence our admonition that no one should ever mention EF without, in the same breath, diastolic volume.
In the 1950s, physiologists used the instantaneous change in SV/EDV (ie, the change in EF) as a measure of change in contractility under conditions of constant load. Over time we have largely forgotten that (1) EF is influenced by both preload (diastolic) and afterload (systolic) and cannot be interpreted as an index of contractility without knowledge of left ventricular (LV) loads; and (2) structural changes leading to increases or decreases in LVEDV will strongly influence the EF at a given level of contractility and SV. So EF is twice removed from an …