6th May 2025

Classification

There are multiple different classification systems for heart failure. Traditionally, heart failure was classified by the main clinical symptoms reported by the patient and could be classified as right ventricular heart failure, left ventricular heart failure. In chronic heart failure, symptoms of either right sided and left sided ventricular failure rarely present in isolation and more commonly present as a combination of both in biventricular heart failure.

Right ventricular heart failure

Blood from the systemic circulation is pumped into the right ventricle, hence right ventricular dysfunction will result in fluid overload symptoms proximal to this. Patients most commonly report bilateral peripheral oedema and abdominal distension (secondary to hepatic congestion).

Left ventricular heart failure 

Blood from the pulmonary circulation feeds into the left ventricle. Left sided ventricular dysfunction causes a build up of fluid in the pulmonary circulation and patients may report breathlessness, paroxysmal nocturnal dyspnoea, orthopnoea and a productive cough. 

Heart failure can also be classified as high output or low output heart failure.

Low output heart failure 

Low output heart failure is the ‘classical’ form of heart failure, characterised by decreased cardiac output due to left ventricular systolic or diastolic dysfunction, typically caused by myocardial infarctions or large pulmonary emboli. 

High output heart failure 

This is a less common form of heart failure and reflects the inability of the heart to meet the body’s increased metabolic demand. This is defined as a resting cardiac output of >8L/min or a cardiac index of >3.9/min/m2. Common causes of high output heart failure include: hyperthyroidism, myeloproliferative disorders, sepsis, thiamine deficiency, arteriovenous fistulae,  pregnancy.

Left ventricular ejection fraction

The most recent guidance introduces a standardised classification of heart failure by the left ventricle ejection fraction. The universal definition of heart failure is a clinical syndrome with current or prior signs and symptoms caused by a structural and/or functional abnormality determined by an ejection fraction of <50% and corroborated with either an elevated natriuretic peptide level or objective evidence of cardiogenic pulmonary or systemic congestion.

Table 5: Classification of heart failure by left ventricular ejection fraction