Heart explained

Your heart is a vital organ. It is a muscle that pumps blood to all parts of your body. The blood pumped by your heart provides your body with the oxygen and nutrients it needs to function.

Your heart is about the size of a clenched fist, and weighs between 300 and 450 g. It lies in the middle of your chest, behind and slightly to the left of your breastbone.

If you are of average body weight and size, your body contains about five litres of blood, all of which passes through your heart every minute or so. When necessary, such as during exercise, your heart can pump up to four times that amount per minute.

The four chambers of the heart

Your heart has a right and left side separated by a wall called the septum. On each side of the wall, there is a small collecting chamber called an ‘atrium’, which leads into a large pumping chamber called a ‘ventricle’. There are four chambers: the left atrium and right atrium (upper chambers), and the left ventricle and right ventricle (lower chambers).

The right side of your heart collects blood on its return from the rest of your body. The blood entering the right side of your heart is low in oxygen. Your heart pumps the blood from the right side of your heart to your lungs so it can receive more oxygen.

Once it has received oxygen, the blood returns directly to the left side of your heart, which then pumps it out again to all parts of your body through an artery called the aorta.

Blood pressure refers to the amount of force the pumping blood exerts on arterial walls.

The heartbeat

Each atrium is connected to its ventricle by a one-way valve. The valve on the right side of the heart is called the tricuspid valve, while the valve on the left side is called the mitral valve.

The familiar 'lub-dub' sound of the heartbeat is caused by the rhythmic closing of the heart valves as blood is pumped in and out of the chambers.

The heart rate is regulated by a special cluster of cells in the right atrium, called the sinus node. The sinus node prompts the upper chambers to contract first. Then, an electrical impulse is sent to a second cluster of cells (the atrioventricular node), which is found between the upper and lower chambers of the heart. The electrical impulse causes the lower chambers to contract. At rest, your heart beats approximately 60 to 100 times a minute.

Blood vessels of the heart

The blood vessels of the heart include:

• coronary arteries – like any other organ or tissue, the heart needs oxygen. The coronary arteries sit on the surface of the heart and supply the heart muscle with blood and oxygen
• aorta – this is the largest artery in the body. Oxygen-rich blood is pumped into the aorta from the left ventricle. The aorta divides into various branches that deliver blood all around the body
• pulmonary arteries – blood low in oxygen is pumped by the right ventricle into the pulmonary arteries that link to the lungs
• pulmonary veins – the pulmonary veins return oxygen-rich blood from the lungs to the left atrium of the heart
• venae cavae –blood low in oxygen is delivered to the right atrium by two veins. One (superior vena cava) carries blood from the head and upper torso, while the other (inferior vena cava) carries blood from the lower body

Common heart conditions

There are many different types of heart conditions. Some common heart conditions include:

• coronary heart disease – coronary heart disease happens when the coronary arteries supplying blood to the heart muscle become blocked or narrowed by a build-up of fatty deposits (plaque). Coronary heart disease can cause angina and heart attacks.
• angina – a type of chest pain caused by a build-up of plaque in the coronary arteries. Part of the heart muscle may not receive enough blood and oxygen. This causes chest tightness, discomfort or pain.. Pain or discomfort may also be felt in the arms, neck, jaw, shoulders or back
• heart attack – happens when something, usually a blood clot, cuts off the flow of blood to the heart. Without oxygen and nutrients, the heart muscle begins to die. A heart attack may not be fatal, especially if you receive immediate medical treatment, but it can still cause lasting damage to the heart.
• heart failure – a condition where the heart is not able to pump blood and oxygen around the body as well as it should
• abnormal heart rhythms (arrhythmias) - a range of conditions where there is a fault in the heart’s electrical system, which affects your heart’s pumping rhythm. Atrial fibrillation is the most common type of abnormal heart rhythm, where the heart beats irregularly and often fast
• heart valve disease – when the heart valve or valves don’t open or close properly. Damage to the heart valves can make it harder for the heart to pump blood around the body
• congenital heart disease – problems with the heart or blood vessels that you are born with. Problems include the blockage of blood flow inside the heart or blood vessels, abnormal flow of blood within the heart, or the heart may not have developed properly.
• heart inflammation – includes pericarditis (inflammation of the outer lining of the heart) andand myocarditis (inflammation of the heart muscle)
• rheumatic heart disease - damage to the valves in the heart that develops after acute rheumatic fever. Rheumatic heart disease affects more Aboriginal and/or Torres Strait Islander Peoples, Maori and Pacific Islander Peoples, and those who have migrated to Australia from low to middle income countries where this disease remains common.

Symptoms of heart disease

‘Heart disease’ is a broad term for different conditions affecting the heart.

Different heart conditions can have different symptoms.

It’s important to be aware of the following symptoms, which can be a warning sign of a medical emergency, including a heart attack:

• Chest discomfort or pain. This can feel like uncomfortable pressure, aching, numbness, squeezing, fullness or pain in your chest. This discomfort can spread to your arms, neck, jaw, shoulders or back. It can last for several minutes or come and go.
• Shortness of breath or difficulty breathing (with or without chest discomfort)
• Racing heart or a feeling of your heart pounding or fluttering in your chest (palpitations)
• Light headedness, dizziness, feeling faint
• Feeling anxious
• Nausea, indigestion, vomiting
• Sweating or a cold sweat.

If your symptoms last more than 10 minutes, are severe or getting worse, call triple zero (000) immediately for an ambulance.

Where to get help

• In an emergency, call triple zero (000) for an ambulance. Don’t drive yourself to hospital.
• Your GP (doctor).
• Cardiologist.