The heart is unable to pump sufficiently to maintain blood flow to meet the body's needs

Aetiology

High output heart failure

• Refers to a heart that has a normal cardiac output, but there is an increase in peripheral metabolic demands that the heart is unable to meet
• Causes include:
  • Anaemia
  • Arteriovenous malformation
  • Paget's disease
  • Pregnancy
  • Thyrotoxicosis
  • Thiamine deficiency (wet Beri-Beri)

Low output heart failure

• Occurs when cardiac output is reduced due to a primary problem with the heart and the heart is unable to meet the body's needs
• Causes of systolic (reduced ejection fraction) HF include:
  • Ischaemic heart disease
  • Dilated cardiomyopathy
  • Myocarditis
  • Infiltration (haemochromatosis or sarcoidosis)
• Causes of diastolic (preserved ejection fraction) HF include:
  • Uncontrolled chronic hypertension (significant left ventricular hypertrophy reduces filling of the left ventricle)
  • Hypertrophic cardiomyopathy
  • Cardiac tamponade
  • Constrictive pericarditis

Pathophysiology

Underlying mechanism of reduced cardiac output

• Ejection fraction: the percentage of blood that is pumped out of the heart during each beat (SV/EDV x 100)

Heart failure with reduced ejection fraction

• Ejection fraction <40%
• Reduced contractility → systolic ventricular dysfunction → decreased LVEF → decreased cardiac output

Heart failure with preserved left ventricular ejection fraction

• Consisting of symptoms and signs of heart failure with an ejection fraction of >50%
• Decreased ventricular compliance → diastolic ventricular dysfunction → reduced ventricular filling and increased diastolic pressure → decreased cardiac output

Left-sided heart failure (HFrEF and/or HRpEF)

• Increased left ventricular afterload - increased mean aortic pressure (e.g. arterial hypertension) or by outflow obstruction (e.g. aortic stenosis)