Heart failure with non-reduced ejection fraction: Epidemiology, pathophysiology, phenotypes, diagnosis and treatment approaches.

Heart failure (HF) has been classified as reduced ejection fraction (HFrEF), mildly reduced ejection fraction (HFmrEF) and preserved ejection fraction (HFpEF) by the recent HF guidelines. In addition, HF with improved ejection fraction has been defined as a subgroup of HFrEF. In HFrEF, diagnostic workup and evidence-based pharmacological and device-based therapies have been well established. However, HFpEF, which comprises almost half of the HF population, represents significant uncertainties regarding its pathophysiology, clinical phenotypes, diagnosis and treatment. Diagnostic criteria of HFpEF have been changed a few times over the years and still remained a matter of debate. New paradigms including a prominent role of co-morbidities, inflammation, endothelial dysfunction have been proposed in its pathophysiology. As a complex, multifactorial syndrome HFpEF consists of many overlapping clinical and hemodynamic phenotypes. In contrast to HFrEF, clinical outcomes of HFpEF have not improved over the last decades due to lack of proven effective therapies. Although HFrEF and HFpEF have different clinical spectrums and proposed pathophysiological mechanisms, there is no clear defining syndrome postulated for HFmrEF. Clinical characteristics and risk factors of HFmrEF overlap with HFrEF and HFpEF. HFmrEF is also referred as a transitional zone for dynamic temporal changes in EF. So, HFpEF and HFmrEF, both namely HF with non-reduced ejection fraction (HF-NEF), have some challenges in the management of HF. The purpose of this paper is to provide a comprehensive review including epidemiology, pathophysiology, clinical presentation and phenotypes of HF-NEF and to guide clinicians for the diagnosis and therapeutic approaches based on the available data in the literature.