Heart disease is a general term that refers to a variety of acute and chronic medical conditions that affect one or more of the components of the heart. The heart is a muscular, fist-sized organ that is located in the centre of the chest cavity. It continuously pumps blood, beating as many as 100,000 times a day. The blood that the heart moves carries oxygen and nutrients throughout the body and transports carbon dioxide and other wastes to the lungs, kidneys and liver for removal. The heart ensures its own blood supply through a set of coronary arteries and veins. The heart is also an endocrine organ that produces the hormones atrial natriuretic peptide (ANP) and B-natriuretic peptide (BNP) which coordinate heart function with blood vessel and kidney function.
The heart is hollow. It is divided vertically into two halves by a septum, and each side of the heart has two internal chambers – an atrium on top and a ventricle on the bottom. Venous blood enters the right side of the heart through the right atrium and is pumped by the right ventricle to the lungs, where carbon dioxide is released and oxygen acquired. Oxygenated blood from the lungs is transported to the left atrium and is pumped by the left ventricle into arteries that carry it throughout the body. Four heart valves regulate the direction and flow of blood through the chambers of the heart. It is their opening and shutting that gives the heart beat its characteristic “lub-dub” sound. The heart muscle itself is called the myocardium. Lining the chambers of the heart and the valves is a membrane called the endocardium. Encasing the outside of the heart is the pericardium – a layered membrane that is fibrous on the outside and serous (fluid-secreting) on the inside. The pericardium forms a protective barrier around the heart and allows it to beat in a virtually friction free environment.
Diseases affecting the heart may be structural or functional. Anything that damages the heart or decreases the heart’s supply of oxygen makes it less efficient, reduces its ability to fill and pump, and disrupts its coordinating relationship with blood vessels and the kidneys, so harming not only the heart but the rest of the body as well.