Paris Heart Centre

How the heart works

The heart is a specialised muscle pump which is designed to move blood around the body to supply vital organs with oxygen. It is divided into 4 parts known as chambers. There are two small chambers at the top of the heart (the right atrium and the left atrium) and two larger chambers at the bottom of the heart ( the right ventricle and the left ventricle). The left ventricle is the main pumping chamber.

The heart is made to pump by a special electrical system which runs throughout the heart. Each normal heart beat begins in the natural pacemaker of the heart (the sino-atrial or SA node) which lies in the right atrium. Electricity passes down the heart to a junction box (atrio-ventricular or AV node) which lies between the upper and lower chambers of the heart.

The AV node is the only way down into the bottom chambers normally. After passing through the AV node, electricity spreads through the left and right ventricles and causes the heart to pump.

In some people there are disturbances in the electrical system which may cause symptoms such as palpitations, light headedness, fainting, chest pain or shortness of breath. These disturbances may be caused by faults in the normal electrical system (often referred to as 'pathways').

We can test the way that the electricity works in the heart by doing a test known as an Electrophysiology study. This tells us if the electrical pathways in the heart are working normally or if there are extra pathways that are causing problems.

Since the heart itself is living tissue, it needs to be supplied with fresh blood. The heart muscle is fed from the coronary arteries. When this supply of blood is interrupted or blocked the heart muscle can be damaged. This event is commonly know as a heart attack (mycardial infarction). When the coronary arteries are narrowed, due to build up of fatty deposits, the flow of oxygen to the heart muscle is decreased causing pain. This is known as angina.

Each day the heart beats about 100,000 times and pumps about 5,000 gallons of blood. The normal heart at rest beats between 60 and 80 beats a minute.

The heart is actually two pumps. The left side receives fresh blood from the lungs and pumps it around the body. The left side is therefore stronger as it has to do more work. The right side of the heart receives de-oxygenated blood from the body and pumps it to the lungs. Since the lungs are close to the heart, the right side is weaker.

Normal heart ECG trace