Human heart has 4 chambers, two atria & two ventricles. The right side receives impure blood from various parts of the body & pumps it into the lungs for oxygenation. The left side receives oxygenated blood from lungs & pumps into various parts of body. By supplying blood to various parts, the heart delivers the oxygen & nutrients to all tissues to meet their metabolic demands.

The heart circulates blood through two pathways: the pulmonary circuit and the systemic circuit.

In the pulmonary circuit, deoxygenated blood leaves the right ventricle of the heart via the pulmonary artery and travels to the lungs, then returns as oxygenated blood to the left atrium of the heart via the pulmonary vein.

In the systemic circuit, oxygenated blood leaves the body via the left ventricle to the aorta, and from there enters the arteries and capillaries where it supplies the body’s tissues with oxygen. Deoxygenated blood returns via veins to the venae cavae, re-entering the heart’s right atrium.

Electrical “pacemaker” cells cause the heart to contract, which happens in five stages. In the first stage (early diastole), the heart is relaxed. Then the atrium contracts (atrial systole) to push blood into the ventricle. Next, the ventricles start contracting without changing volume. Then the ventricles continue contracting while empty. Finally, the ventricles stop contracting and relax. Then the cycle repeats.

Valves prevent backflow, keeping the blood flowing in one direction through the heart.

Facts about the human heart

  • A human heart is roughly the size of a large fist.
  • The heart weighs between 9 and 12 ounces (250 and 350 grams).
  • The heart beats about 100,000 times per day (about three billion beats in a lifetime).
  • An adult heart beats about 60 to 80 times per minute.
  • Newborns hearts beat faster than adult hearts, about 70 -190 beats per minute.
  • The heart pumps about 6 quarts (5.7 liters) of blood throughout the body.
  • The heart is located in the center of the chest, usually pointing slightly left.

What is heart failure?

The heart muscle is weaker than normal and not able to pump the blood at a rate commensurate with the body needs or the lower chambers of the heart are not able to relax and fill with blood as they normally do.

Less blood is pumped out of the heart to organs and tissues in the body.

Pressure in the heart increases.

Heart Failure doesn't mean that your heart has stopped working

When the heart cannot pump enough oxygen and nutrients to meet the body’s needs; it tries to adapt. The chambers of the heart stretch to hold more blood to pump through the body with each heartbeat.

Hormones are released into the bloodstream to increase the heart’s pumping power and increase blood flow into the heart chambers. These changes provide temporary relief, but over time, the heart muscle walls continue to weaken and/ or stiffen.

Two types of heart failure

Systolic left ventricular dysfunction (or systolic heart failure) occurs when the left ventricle doesn’t contract with enough force, so less oxygen-rich blood is pumped throughout the body.

Heart failure with preserved left ventricular function (diastolic heart failure) occurs when the heart contracts normally, but the ventricles do not relax properly or are stiff and less blood enters the heart during normal filling.

What causes heart failure?

The following conditions can cause heart failure:

  • Heart valve disease
  • Coronary artery disease
  • Diabetes mellitus
  • Kidney failure
  • Heart muscle disease
  • Anaemia
  • Hypertension
  • Chronic lung disease
  • Heart rhythm abnormalities (atrial fibrillation etc)

Doctors say that by themselves the signs of heart failure may not mean the patient has heart failure and he/ she should not be alarmed. However, people who have not been diagnosed with heart failure and experience more than one of the symptoms below should tell their doctor and ask for an evaluation of their heart. People who have been diagnosed with heart failure should monitor their symptoms carefully and report any sudden changes to their doctor immediately.

Main symptom

By far the main symptom is extreme fatigue. The patient is not getting enough blood pumped from the heart to his/ her muscles. The body diverts blood away from less vital organs – muscles in the limbs – and focuses on supplying to the heart and brain. Other symptoms depend on which part of the heart is predominantly involved.

Symptoms for Left heart failure

  • Breathlessness, panting (dyspnea) – this may happen at any time, but will be more noticeable or acute when the patient is active or lying down. At night will often need to sit up in bed or will have an urge to get some fresh air.
  • Cough
  • Frothy spit (with the cough) – This happens when blood backs up in the pulmonary veins because the heart cannot keep up with the supply, causing fluid to leak into the lungs.

Symptoms for right heart failure

  • Swollen ankles
  • Swollen legs
  • Enlarged liver
  • Enlarged stomach – This happens because as blood flow from the heart slows down, blood that returns to the heart through the veins backs up, causing fluid accumulation in the tissues. Kidneys find it harder to dispose of sodium and water, which in turn causes fluid retention in the tissues.

Heart failure involving both ventricles will result in combination of symptoms and signs listed above.

Diagnostics / Evaluation of heart failure

The following tests are used to diagnose the heart failure:

Echocardiography (Echo)

Echocardiography (echo) is a painless test that uses sound waves to create pictures of your heart. This test gives your doctor information about the size and shape of your heart and how well your heart’s chambers and valves are working. It measures the ejection fraction of the heart.

Peak oxygen consumption test

Maximum oxygen consumption, also referred to as VO2max is one of the oldest fitness indices established for the measure of human performance. The ability to consume oxygen ultimately determines any human’s or animal’s ability for maximal work output over periods lasting greater than one minute.

Cardiac catheterisation

Cardiac catheterisation is a medical procedure used to diagnose and treat some heart conditions. A long, thin, flexible tube called a catheter is put into a blood vessel in your arm, groin (upper thigh), or neck and threaded to your heart.

Six minute walk test

The purpose of the six minute walk is to test exercise tolerance in chronic respiratory disease and heart failure. The six-minute walk test (6MWT) measures the distance an individual is able to walk over a total of six minutes on a hard, flat surface. The goal is for the individual to walk as far as possible in six minutes. The individual is allowed to self-pace and rest as needed as they traverse back and forth along a marked walkway.

NT-Pro-BNP test

When heart failure develops or worsens, the ventricles or lower chambers of the heart produce a substance that breaks down to form two proteins: B-type natriuretic peptide (BNP) and N-terminal-pro-BNP (NT-pro-BNP). Both substances are secreted in response to changes in pressure that occur with heart failure. These tests measure the concentration of B-type natriuretic peptide (BNP) or N-terminal pro B-type natriuretic peptide (NT-proBNP) in the blood in order to detect and evaluate heart failure.

ST2 test

Cardiac biomarkers are substances that are released into the bloodstream when the heart is damaged or stressed. In patients with heart failure, measurement of these biomarkers is used to help risk stratify, to assess treatment options, monitor progress, and guide in-hospital and post-discharge care. ST2 is one such biomarker. ST2 is a soluble protein expressed by the heart in response to disease or injury. Unlike many other cardiac biomarkers, ST2 levels change quickly in response to changes in the patient’s condition—thus helping physicians make informed decisions on an appropriate course of action to take and, if needed, to quickly adjust treatment.

For people who have healthy heart

If you have a healthy heart, you can take action to prevent heart disease and heart failure. To reduce your risk of heart disease:

  • Follow a healthy diet. A healthy diet includes a variety of vegetables and fruits. It also includes whole grains, fat-free or low-fat dairy products, and protein foods. A healthy diet is low in sodium (salt), added sugars, solid fats, and refined grains.
  • If you smoke, make an effort to quit. Talk with your doctor about programs and products that can help you quit smoking. Also, try to avoid secondhand smoke.
  • If you’re overweight or obese, try to lose weight. Work with your health care team to create a reasonable weight-loss plan.
  • Be physically active. People gain health benefits from as little as 60 minutes of moderate-intensity aerobic activity per week. The more active you are, the more you will benefit.
  • Avoid using illegal drugs.

For people who are at risk of heart failure

Even if you're at high risk for heart failure, you can take steps to reduce your risk. People at high risk include those who have coronary heart disease, high blood pressure, or diabetes.

  • Follow all of the steps listed above. Talk with your doctor about what types and amounts of physical activity are safe for you.
  • Treat and control any conditions that can cause heart failure. Take medicines as your doctor prescribes.
  • Avoid drinking alcohol.
  • See your doctor for ongoing care.

Heart failure can cause other extreme complications that include:

Kidney failure

Heart failure if left untreated can eventually cause kidney failure because of the reduced blood flow to kidneys.

Heart valve problems

Complications might arise if the heart is enlarged or it the pressure in the heart is very high due to heart failure.

Liver Damage

Heart failure may lead to fluid accumulation that puts extreme pressure on the liver; thus making it difficult for liver to function properly.


Due to reduced blood flow through the heart in case of heart failure, it’s more likely one will develop blood clots, which can increase the risk of having a stroke.