Heart Failure

Heart failure occurs when the heart is unable to pump blood as effectively as the body needs, either because it cannot contract with enough force, cannot relax and fill properly between beats, or both. Despite its name, heart failure does not mean the heart has stopped working — it means the heart needs support to work as well as it should, and with modern treatment, many people with heart failure lead active, stable lives for years.

Heart failure can occur at any age but becomes considerably more common with age, and it is generally a chronic, long-term condition rather than a single event — though it can also develop suddenly, and can worsen suddenly even in someone previously stable, which is when it becomes a genuine emergency. Treatment for heart failure has advanced considerably in recent years, with several newer medication classes now shown to meaningfully extend life and keep people out of hospital, on top of the more familiar treatments used for decades.

How the Heart Compensates and Why This Becomes a Problem

When the heart's pumping ability first begins to decline, the body activates several compensatory mechanisms to try to maintain adequate blood flow: the heart muscle can enlarge or thicken, the heart rate increases, and hormonal systems (including the renin-angiotensin-aldosterone system and the sympathetic nervous system) are activated to raise blood pressure and retain fluid, boosting the volume of blood the heart has to work with.

In the short term, these changes help maintain blood flow to vital organs. Over time, however, they become part of the problem rather than the solution — the enlarged heart muscle becomes less efficient, the persistently activated hormonal systems cause further strain and fluid retention, and this fluid retention is precisely what causes the fluid build-up in the lungs, liver, and legs that characterises worsening heart failure. This is also why many of the most effective heart failure medications work by specifically blocking these compensatory hormonal pathways — not by making the heart pump harder, but by interrupting the harmful cycle the body's own compensation creates.

Types of Heart Failure

Heart failure can be classified in two complementary ways: by which side of the heart is primarily affected, and, more importantly for guiding treatment, by ejection fraction — the percentage of blood the left ventricle pumps out with each contraction.

Left-Sided Heart Failure

Left-Sided Heart Failure The most common type. The left ventricle cannot pump efficiently, so blood backs up into the lungs, causing breathlessness and fluid build-up. Can be further divided by ejection fraction (see below).

Often triggered by left-sided failure, as the right ventricle has to work harder against the resulting congestion in the lungs. Blood backs up into the abdomen, legs, and feet, causing swelling and, in the abdomen, fluid accumulation (ascites).

Heart Failure with Reduced Ejection Fraction (HFrEF) Ejection fraction of 40% or below — the heart muscle has lost much of its ability to contract forcefully (a “pumping problem”). This is the category with the strongest evidence base for medication that meaningfully improves survival.

Heart Failure with Mildly Reduced Ejection Fraction (HFmrEF)

Ejection fraction of 41–49%, an intermediate category that shares features of, and treatment overlap with, both HFrEF and HFpEF.

Heart Failure with Preserved Ejection Fraction (HFpEF)

Heart Failure with Preserved Ejection Fraction (HFpEF) Ejection fraction of 50% or above — the heart contracts normally but the left ventricle is stiff and cannot relax and fill properly (a “filling problem”). More common in women, and often associated with high blood pressure, obesity, and diabetes.

How Heart Failure Severity Is Graded

Beyond the type of heart failure, doctors also grade how much it is limiting a person's daily life, using a widely used framework called the New York Heart Association (NYHA) functional classification. This matters because it guides treatment intensity and helps track whether someone is improving or worsening over time, independent of the specific ejection fraction measurement.

• Class I: No limitation; ordinary physical activity does not cause undue fatigue, breathlessness, or palpitations.
• Class II: Mild limitation; comfortable at rest, but ordinary activity results in fatigue, breathlessness, or palpitations.
• Class III: Marked limitation; comfortable at rest, but less-than-ordinary activity causes symptoms.
• Class IV: Unable to carry out any physical activity without symptoms; symptoms may be present even at rest.

Symptoms of Heart Failure

• Shortness of breath, particularly with exertion or when lying flat
• Swelling in the legs, ankles, and feet
• Bloating, or swelling in the abdomen
• Fatigue and weakness
• Rapid or irregular heartbeat
• Persistent cough or congested lungs
• Increased need to urinate at night
• Loss of appetite and nausea
• Sudden weight gain from fluid retention
• Difficulty concentrating or reduced alertness

Risk Factors of Heart Failure?

• Coronary artery disease and prior heart attack, it is the most common underlying cause
• High blood pressure, which forces the heart to work harder over time
• Cardiomyopathy 
• Arrhythmias, particularly persistent or poorly controlled atrial fibrillation
• Congenital heart disease
• Heart valve disease
• Diabetes and obesity
• Chronic kidney disease

How is Heart Failure Diagnosed

• Echocardiogram: Echocardiogram An ultrasound of the heart assessing its structure, movement, and pumping function — the key test used to measure ejection fraction and determine which category of heart failure is present, which directly shapes treatment.
• Blood Tests: Check organ function, cholesterol, and for anaemia, and can measure natriuretic peptides (BNP or NT-proBNP), substances released by a strained heart that help confirm the diagnosis and gauge severity.
• Electrocardiogram (ECG): Electrocardiogram (ECG) Records the heart's electrical activity, helping identify arrhythmias, prior heart attacks, or other electrical abnormalities contributing to heart failure.
• Cardiac Catheterisation: An invasive procedure in which a catheter is guided into the heart's blood vessels to directly assess blood flow, used particularly to determine whether coronary artery disease is an underlying cause.
• Cardiac Imaging (CT or Additional Ultrasound): Assesses heart size and detects fluid build-up around the heart or in surrounding organs.
• Cardiac Stress Test: Monitors heart function during exercise, providing information about the likelihood of underlying coronary artery disease as a contributing cause.

Reducing Your Risk of Heart Failure

• Quit smoking, since toxic chemicals in cigarettes damage the heart and blood vessels and lower blood oxygen, raising blood pressure and heart rate
• Exercise regularly, which lowers the risk of heart disease and helps control weight and other chronic conditions
• Eat a heart-healthy diet to protect the heart and improve blood pressure and cholesterol
• Maintain a healthy weight — even modest weight loss can meaningfully help if you are overweight
• Attend regular health screening, since high blood pressure and high cholesterol are often silent until they cause complications
• Manage stress through sustainable strategies such as exercise, relaxation techniques, or mindfulness, rather than through smoking, overeating, or alcohol
• If you have an existing heart condition, attend regular follow-up and monitor your weight at home — rapid weight gain is often the earliest sign of fluid retention, before breathlessness or swelling become obvious