What Is Left-Sided Heart Failure

  • Helen McLachlan MSc Molecular Biology & Pathology of Viruses, Imperial College London
  • Zayan Siddiqui BSc in Chemistry with Biomedicine, KCL, MSc in Drug Discovery and Pharma Management, UCL


Heart failure is a serious health condition. It is defined as a clinical syndrome with symptoms of breathlessness, swelling of the ankles and fatigue in the presence of an abnormality in the structure or function of the heart.1 The terms right- and left-sided heart failure were previously used, but as they can be misleading, they are no longer used.1

The heart is a pump delivering blood carrying oxygen to our body to meet our daily needs.2 Changes in the heart's structure or function may impact and impair the ability of the heart to function and meet the body's needs. This is when symptoms become apparent. 

To understand the causes of heart failure, we first need to understand the anatomy of the heart. The heart is a pump with four chambers, two on the left side and two on the right. Blood comes into the heart from the body on the right side and then gets pumped to the lungs from the right ventricle to pick up fresh oxygen (figure 1). Coming from the lungs and fresh with oxygen, the blood is delivered to the left side of the heart – to the left atrium, to be pumped to the whole body from the left ventricle to deliver this oxygen, as shown in Figure 1. 

Figure 1. Structure of the heart3

Valves sit between the four chambers (right atrium, right ventricle, left atrium and left ventricle), preventing the blood from going in the wrong direction. 

The heart is made of muscle, and for it to contract, to pump, it needs an electrical signal to travel across the heart in stages to tell it what to do.2 This electrical signal starts in the right atrium (RA) and crosses both atria, making them contract, thereby pushing blood through the one-way valves into the receiving ventricle chambers (figure 1).2 The electrical impulse is then sent via another area of special tissue to spread to the ventricles, causing them to contract. This contraction pushes blood through valves – to the lungs from the right ventricle and to the body from the left ventricle.2 

Blood pressure 

The blood in the body has to be under a certain amount of pressure to deliver blood to the whole body. This pressure is created from the pumping action of your heart, the elasticity (stretchiness) and size of your vessels and chambers of the heart, and the thickness of the blood.2 

Causes of heart failure 

When the pumping action of the heart is compromised or damaged, this can give rise to heart failure and its associated symptoms.

Myocardial causes: 

These ensue when problems in the muscular wall of the heart affect its ability to pump.2, and include:

Coronary artery disease

Coronary artery disease is the most common cause, and happens when there is disease in the blood vessels that carry blood to the muscle wall of the heart. In turn, conditions that can worsen this include diabetes mellitus, high blood pressure (hypertension) and high cholesterol.3 Coronary artery disease includes conditions of angina and heart attacks

High blood pressure (hypertension) 

If the left ventricle has to work harder against more resistance to pump the blood around the body, it can lead to a weakened left ventricle wall and reduced ability to pump, causing hypertension.3


Cardiomyopathies can have various causes, including familial, toxins (e.g. alcohol) and pregnancy. They are diseases of the walls of the heart chamber where the walls can become stretched, stiff or thickened, impairing their ability to pump.4

Valve disease 

On the left side of the heart, the mitral valve sits between the left atrium and left ventricle, allowing blood to flow only in that direction, and the aortic valve sits at the exit of the left ventricle where the blood flows into the aorta, the main artery of the body.1,2 These valves can become hardened and resistant to the blood flow, or they can become loose and allow blood to flow back in the wrong direction. Both of these actions can damage the muscle wall of the heart, causing valve disease.


Arrhythmia occurs when the electrical impulses and heartbeats are abnormal.1 2

Congenital heart disease 

Congenital heart disease occurs when a person is born with a heart condition resulting in muscle wall abnormalities or disruption to normal blood flow.1

Excess volume

This can occur as a result of kidney failure.1


Many factors linked to obesity cause heart failure.1 

Signs and symptoms

Symptoms include the following:1,2 

  • Breathlessness, including breathlessness when lying flat
  • Waking in the night suddenly due to breathlessness
  • Reduction in ability to exercise
  • Swelling in the peripheries/ ankles
  • Fatigue/tiredness
  • Increased pressure in the jugular vein seen in the neck
  • Lung crackles on listening with the stethoscope


A recent definition proposed by a committee consisting of 14 countries defines heart failure in a standardised way as below and can be used for diagnosis.5

Symptoms of heart failure caused by a structural or functional disorder (e.g. heart chamber enlargement, valvular abnormality, enlargement of the muscular ventricle wall) alongside either – a raised natriuretic peptide level in the blood or evidence of congestion (clogging), for example, raised pressure evidenced by x-rays of the lungs or signs of raised pressure in the jugular vein.5

The natriuretic peptides are released from the atria and ventricles in response to volume and pressure, and their levels rise in heart failure.6

As part of the diagnosis, a patient will have a full history taken, including symptoms and background history of medical conditions. They will be examined for signs and symptoms in addition to murmurs to suggest valvular conditions. Investigations will include:6

  • ECG
  • Blood pressure
  • Blood tests assessing for raised natriuretic peptide levels
  • A chest x-ray will look for congestion in the lungs and the size of the heart and exclude other causes of breathlessness. 
  • An echo test (ultrasound test of the heart) is used to assess how well the heart is pumping, known as the ejection fraction, and to assess for valvular disease. The ejection fraction is the percentage of blood ejected from the ventricle with each heartbeat and represents the performance of the left ventricle.7 

Diagnosis can also involve staging the heart failure, and various staging classifications can be used. Common ones include the New York Heart Association (NYHA) based on the severity of symptoms classed I, II, III and IV and the American Heart Association (AMA) stages A-D based on heart failure symptoms worsening and structural changes of the heart.1,5

Management and treatment of heart failure

Lifestyle changes 

These include eating a healthily balanced diet, stopping smoking and exercising as part of a cardiac rehabilitation programme.1,8,9


Standard medicines used to treat heart failure include:8,9

These medications help the blood vessels in your body relax and widen, making it easier for the heart to pump blood to the body and reduce the work it has to do

These medications work similarly to ACE inhibitors

Beta-blockers slow the heart rate and reduce blood pressure, again reducing the work on the heart.

If the heart pump is not working as well as it should, fluid can build up in the body, causing swelling/ leg oedema or in the lungs, causing breathlessness. Diuretics result in passing out more water and salt in your urine so drawing this fluid from the lungs/ankles back into the bloodstream reducing breathlessness and ankle swelling.

These medications block the actions of a chemical, which would normally lead to fluid and salt build up in the body so helping the symptoms of heart failure and reducing the need for hospital admission.

Other medications are available via specialist teams. Digoxin works to help the heart rhythm – this is particularly useful for people with irregular heart rhythms– arrhythmias. Ivabradine can be used as an alternative (or in addition, in special circumstances) to beta blockers as it also slows down the heart rate.

Implanted devices

These devices are placed in the chest to help control or monitor heart rhythms in certain people with heart failure.8 



Atrial fibrillation is the arrhythmia seen most commonly in people with heart failure and is more likely in those who are older and with those with more severe heart failure.1 Arrhythmias of the ventricles are also seen.1


Major depressive disorder is seen in a fifth of those with heart failure.1


Anaemia if present can also worsen heart failure symptoms.1

There is a higher risk of complications from infections, so people with heart failure will be offered vaccinations yearly against the flu and a one-off pneumococcal vaccination.

Kidney disease

This can be chronic kidney disease or acute kidney injury.1

Sudden cardiac death

30-40% of deaths in heart failure are due to sudden cardiac death.1 


How can I prevent heart failure?

Reducing the risk of conditions that can lead to heart failure by stopping smoking, ensuring you do not drink excessive alcohol, exercising and keeping your weight in the healthy range. Should you be diagnosed with high blood pressure or diabetes, ensure you take your treatment to control it and attend your reviews.9

How common is left-sided heart failure?

In the UK, prevalence is age-dependent, increasing with increasing age:1

  • 1 in 35 people aged 65-74
  • 1 in 15 aged 75-85 
  • 1 in 7 aged 85 years and older

Who is at risk of heart failure?

Those who have medical conditions that can cause heart failure, for example, high blood pressure that is not controlled, diabetes, those who have had heart attacks, and those who drink excessive alcohol.

When should I see a doctor?

If you have any of the symptoms above or are concerned by anything you have read please contact your doctor to discuss.


  1. NICE [Internet]. [cited 2023 Oct 6]. CKS is only available in the UK. Available from: https://cks.nice.org.uk/topics/heart-failure-chronic/
  2. How the heart works [Internet]. [cited 2023 Oct 6]. Available from: https://www.nhsinform.scot/illnesses-and-conditions/heart-and-blood-vessels/about-the-heart/how-the-heart-works
  3. British Heart Foundation [Internet]. [cited 2023 Oct 6]. How your heart works. Available from: https://www.bhf.org.uk/informationsupport/how-a-healthy-heart-works
  4. nhs.uk [Internet]. 2017 [cited 2023 Oct 6]. Cardiomyopathy. Available from: https://www.nhs.uk/conditions/cardiomyopathy/
  5. Bozkurt B, Coats AJS, Tsutsui H, Abdelhamid CM, Adamopoulos S, Albert N, et al. Universal definition and classification of heart failure: a report of the Heart Failure Society of America, Heart Failure Association of the European society of Cardiology, Japanese heart failure society and writing committee of the universal definition of heart failure: endorsed by the Canadian heart failure society, heart failure association of India, cardiac society of Australia and new zealand, and Chinese heart failure association. European J of Heart Fail [Internet]. 2021 Mar [cited 2023 Oct 6];23(3):352–80. Available from: https://onlinelibrary.wiley.com/doi/10.1002/ejhf.2115
  6. Heart failure: practice essentials, background, pathophysiology. 2023 Jun 9 [cited 2023 Oct 6]; Available from:https://emedicine.medscape.com/article/163062-overview?icd=login_success_email_match_norm#a3
  7. Ejection fraction - an overview | sciencedirect topics [Internet]. [cited 2023 Oct 6]. Available from: https://www.sciencedirect.com/topics/medicine-and-dentistry/ejection-fraction
  8. nhs.uk [Internet]. 2017 [cited 2023 Oct 6]. Heart failure. Available from: https://www.nhs.uk/conditions/heart-failure/treatment/
  9. Heart failure [Internet]. [cited 2023 Oct 6]. Available from: https://www.nhsinform.scot/illnesses-and-conditions/heart-and-blood-vessels/conditions/heart-failure#treating-heart-failure
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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