How the Heart Works

The human heart has four chambers. The two upper chambers are called the atria. The two lower chambers are called the ventricles. The atria receive blood returning to the heart, and then push it downward to the ventricles. The ventricles, which are larger and stronger, give departing blood a push outward towards its destination.

The heart is in fact two pumps. The right side receives de-oxygenated blood from the body and pumps blood to the lungs to pick up oxygen. The much stronger left ventricle takes oxygenated blood coming back from the lungs and circulates it to the rest of the body.

Blood flows through the body in an endless, figure-eight loop.

1. The right ventricle pumps blood to the lungs so it can get oxygen.

2. Blood returning from the lungs arrives in the left atrium, which pushes if downward to the left ventricle.
   
   
   
   

3. The left ventricle pumps blood out to rest of the body, taking the oxygen out where it will be used by muscles and other tissues to do their work.
   
4. Blood returning from various parts of the body arrives in the right atrium. From there it goes to the right ventricle for another trip through the lungs so it can get more oxygen, and the cycle continues.

Blood circulates in two loops as it flows through the heart.

• Your heart has four chambers:

The right atrium: Receives venous blood from the body

The right ventricle: Pumps venous blood to the lungs for oxygen

The left atrium: Receives oxygenated blood from the lungs

The left ventricle: Pumps blood out to the body through the arteries

Normally, the right side pumps blood only to the lungs. The left side pumps blood to the rest of the body. For that reason, the left side needs to pump harder; generally, there's three to four times as much pressure on the left side.

Valves control the direction of blood from the atrium to the ventricle,and from the ventricles into the main arteries.

Heart defects like Atrial Septal Defect (ASD), Ventricular Septal Defect (VSD), or Patent Ductus Arteriosus (PDA) allow blood to escape from the left to the right side through an abnormal hole or passageway. Doctors call this a "left to right shunt". The exception is Patent Foramen Ovale (PFO); which is a right to left shunt.

The heart is made of strong muscle, called myocardium, and sits in a sac of fibrous tissue - the pericardium. The heart's inner surface, which is in contact with the blood being pumped, is called the endocardium.

CORONARY ARTERIES

The coronary arteries supply blood to the heart. They arise just distal to the aortic valve in the Sinuses of Valsalva and traverse the heart's outer surface.

The right coronary artery supplying the right side of the heart, contains only one major branch, while left coronary artery contains two branches, the left anterior descending branch (LAD) and the circumflex branch. Smaller branches from the major branches penetrate the myocardium. About 4 - 5% of the total circulating blood flows through the coronary arteries.

HEART FACTS

• In a healthy, resting adult, the heart beats 60 to 100 times per minute. This amounts to 104,000 beats in 24 hours, or about 2.5 billion beats in an average lifetime of 70 years.

• Coronary disease is the largest single cause of death in Australia , claiming 29,051 lives in 1997. Every day, around 80 Australians die from coronary disease. (Heart Foundation)

• A normal heart recirculates the 5 to 6 litres of blood in the body every 1-½ minutes. This amounts to over 7,000 litres pumped each day.

• During strenuous activity, a healthy heart must pump four to seven times its normal output

• Much of the death, disability and illness caused by cardiovascular disease is preventable.(Heart Foundation)

• In 1995, over 10 million adult Australians (about 80% o the adult population) had at least one of the following cardiovascular risk factors
  
• Tobacco smoking
  
• Physical inactivity
  
• high blood pressure
  
• Overweight

Four out of five men and three in four women had at least one of these risk factors (Heart Foundation)

• In a 1995 survey, over 4.5 million adult Australians (over 1/3 of the adult population) reported doing no leisure-time physical activity in the 2 weeks prior to the interview. People who do not participate in regular physical activity are almost twice as likely to die from coronary heart disease as those who participate. (Heart Foundation)

• Cardiovascular disease is the most costly disease for the healthe system in Australia (Heart Foundation)

• There were 11,348 coronary angioplasty procedures performed in 1995. In around 1/3 of these stents were deployed (Heart Foundation)