Heart

The heart is a muscular organ about the size of a fist, located just behind and slightly left of the breastbone. The heart pumps blood through the network of arteries and veins called the cardiovascular system.
The heart has four chambers:
1. The right atrium receives blood from the veins and pumps it to the right ventricle.
2. The right ventricle receives blood from the right atrium and pumps it to the lungs, where it is loaded with oxygen.
3. The left atrium receives oxygenated blood from the lungs and pumps it to the left ventricle.
4. The left ventricle (the strongest chamber) pumps oxygen-rich blood to the rest of the body. The left ventricle’s vigorous contractions create our blood pressure.

Rhythm disturbances

The primary function of the heart is to supply blood and nutrients to the body. The regular beating, or contraction, of the heart moves the blood throughout the body. Each heartbeat is controlled by electrical impulses traveling through the heart. In the normal heart these electrical impulses occur in regular intervals. When something goes wrong with the heart's electrical system, the heart does not beat regularly. The irregular beating results in a rhythm disorder, or arrhythmia.