Definitions and Historical Considerations – The Misleading Role of Ejection Fraction
Chronic heart failure (CHF) is a heterogeneous syndrome with a complex pathophysiology. Although many different definitions for heart failure exist, we prefer the following: “a clinical syndrome characterised by symptoms and signs of increased tissue/organ water and decreased tissue/organ perfusion. Regardless of its aetiology, symptoms and signs may be related either to impaired left ventricular (LV) relaxation, suction and filling (predominantly diastolic pump dysfunction/failure) or to impaired output of the cardiac compression pump (predominantly systolic pump dysfunction/failure) but almost always to a combination of both.”1
This definition of heart failure refrains from including any notion of LV ejection fraction. However, mostly driven by clinical trial design, heart failure has been dichotomised according to ejection fraction as ‘preserved’ (heart failure with preserved ejection fraction [HFpEF]) or ‘reduced’ (heart failure with reduced ejection fraction [HFredEF]). Recently, epidemiological surveys have revealed that the incidence of HFpEF has been steadily increasing over the past 25 years.2 Currently, the LV ejection fraction is found to be preserved in >50% of cases of heart failure. Patients with HFpEF appear to be older and are more likely to be female, have a history of hypertension and have less coronary artery disease. Once hospitalisation for ‘decompensation’ has occurred, the cardiovascular mortality and overall prognosis is as poor as for HFredEF.2,3
Erroneously, the pathophysiology of HFpEF and HFredEF were considered to be genuinely different. Whereas HFredEF was correlated with mere ‘systolic abnormalities’, these abnormalities were believed to be absent in HFpEF. Instead, when ejection fraction was preserved, heart failure was correlated with ‘diastolic abnormalities’, and was thought to occur without abnormalities in systole. Inevitably, the connotations ‘systolic’ and ‘diastolic’ heart failure were introduced as they were estimated to reflect distinct diseases. However, recent observations have neglected to refine this view.4,5 Most importantly, it is now generally recognised that in systolic heart failure LV diastolic abnormalities are profound, and predict a patient’s symptoms better than systolic (dys)function.6 In contrast, in diastolic heart failure there are marked, previously overlooked LV systolic abnormalities, as revealed by novel cardiac imaging techniques.7 In fact, CHF, irrespective of ejection fraction (even when preserved), is emerging as a syndrome in which many pathophysiological processes interact.