Heart Failure

Definition and ClassificationTop

Heart failure (HF) is a condition in which an abnormal heart structure or function causes a reduction in cardiac output relative to metabolic requirements or in which cardiac output is maintained with an increase in filling pressures. Clinically, HF is a syndrome in which patients have symptoms (eg, shortness of breath, ankle and/or abdominal swelling, fatigue) and signs (eg, elevated jugular venous pressure, pulmonary crackles) of volume or pressure overload.

Heart failure can be classified as:

1) New-onset HF: Occurring for the first time, regardless of the dynamics of symptoms.

2) Acute decompensated HF: A rapid onset of or increase in symptoms and signs of HF.

3) Chronic HF, which can be further classified as stable, progressive, or advanced. Advanced HF represents a subset of chronic HF and is characterized by refractory, “end-stage” symptoms and circulatory compromise despite evidence-informed treatment.

For therapeutic and prognostic purposes, heart failure is also classified according to left ventricular ejection fraction (LVEF), which is defined as stroke volume (end-diastolic minus end-systolic volume) divided by the end-diastolic volume.

1) HF with reduced ejection fraction (HFrEF) is typically defined as clinical HF with ejection fraction (EF) ≤40%.

2) HF with preserved ejection fraction (HFpEF) is typically defined as clinical HF with EF ≥50% and evidence of diastolic dysfunction or elevated LV filling pressure.

The LVEF threshold for the diagnosis of HFrEF and HFpEF has varied across clinical trials and clinical practice guidelines. LVEF between 41% to 49% is considered to be in the gray zone, recently referred to as midrange EF (HFmrEF).

Clinically, HF may also be classified as left ventricular, right ventricular, or biventricular failure, depending on whether the predominant symptoms of congestion are pulmonary, systemic, or both.

High-output HF refers to clinical HF occurring due to increased cardiac output and hyperdynamic states, which may not always be associated with an underlying structural heart disease.