Coronary Heart Disease Overview

Coronary heart disease (CHD), also called coronary artery disease, affects about 14 million men and women in the United States.
Disease develops when a combination of fatty material, calcium, and scar tissue (plaque) builds up in the arteries that supply the heart with blood. Through these arteries, called the coronary arteries, the heart muscle (myocardium) gets the oxygen and other nutrients it needs topump blood.

• The plaque often narrows the artery so that the heart does not get enough blood.
  
• This slowing of blood flow causes chest pain, or angina.
  
• If plaque completely blocks blood flow, it may cause a heart attack (myocardial infarction) or a fatal rhythm disturbance (sudden cardiac arrest).
  
• A major cause of death and disability, coronary heart disease claims more lives in the United States than the next 7 leading causes of death combined.

The heart consists of 4 chambers: an atrium and a ventricle on the right, and an atrium and ventricle on the left.

• Blood returning to the heart from veins all over the body flows into the right atrium.
  
• From there the blood flows into the right ventricle, which pumps it out to the lungs for oxygenation.
  
• The oxygen-rich blood returns to the left atrium.
  
• From there the blood flows into the left ventricle, which pumps it at high pressure into the arteries.
  
• This entire process constitutes one heartbeat.

The pumping, or contraction, of the left ventricle must be very powerful because that is what keeps the blood flowing throughout the body.

• The strength of the heart muscle depends on the oxygen and nutrient supply coming via the coronary arteries.
  
• These arteries are usuallystrong, elastic, and quite flexible.

The heart has 3 major coronary arteries.

• Two of these arteries arise from a common stem, called the left main coronary artery.
  
• The left main coronary artery supplies the left side of the heart.
  
• Its left anterior descending (LAD) branch supplies the front part of the heart.
  
• The left circumflex (LCX) branchsupplies the left lateral and back sideof the heart.
  
• Finally, the right coronary artery (RCA) is separate and supplies the right and the bottom parts of the heart.

As a child, the inner lining of the coronary arteries is quite smooth, allowing blood to flow easily. As a person ages, the cholesterol and calcium content in the walls of the coronary arteries increases, making them thicker and less elastic.

• Unhealthy habits, such as a diet high in cholesterol and other fats, smoking, and lack of exercise accelerate the deposit of fat and calcium within the inner lining of coronary arteries.
  
• This process is known as atherosclerosis, or hardening of the arteries. The deposits, or plaques, eventually obstruct the blood vessel, which begins to restrict blood flow.

Plaque is like a firm shell with a soft inner core containing cholesterol. As blood hits it during each heartbeat, the plaque may crack open and expose its inner cholesterol core, which promotes blood clotting. Clots may further reduce blood flow, causing severe pain (angina), or even block it all together.