Overview

The coronary arteries deliver blood to the heart muscle. The blood provides a continuous supply of oxygen and nutrients needed for the heart to stay healthy and work as it should.

Supply and demand

The coronary arteries regulate the supply of blood to your heart muscle depending on how much oxygen your heart needs at the time. This is shown by:

• The number of times your heart beats per minute (heart rate).
• Your blood pressure.
• The force of your heart's contractions.
• The thickness of your heart muscle.

The harder the heart has to work to pump blood, the more oxygen it needs. For example, when you exercise, your heart rate and blood pressure increase. This in turn increases your heart's demand for oxygen.

The main way to increase the oxygen supply to the heart is to increase the blood flow through the coronary arteries. Your heart increases the blood flow by widening (dilating) your coronary arteries.

If your coronary arteries aren't able to dilate properly, your heart muscle may not be able to get the amount of oxygen it needs to work as it should.

Anatomy of the coronary arteries

Your left ventricle pumps blood into the main artery of your body, called the aorta. Close to the heart, the two main coronary arteries branch off of your aorta.

• The left main coronary artery is a short vessel that branches into the:
  • Left anterior descending artery. It supplies blood to the front (anterior wall) and part of the side (anterolateral wall) of the left ventricle, to the top of the left ventricle, and to most of the wall between the ventricles (interventricular septum).
  • Circumflex artery, which passes behind the heart between the left atrium and left ventricle. It supplies blood to the side (lateral wall) of the left ventricle. In a small number of people, the circumflex artery supplies the lower and back portions of the left ventricle.
• The right coronary artery supplies blood to the right ventricle. It then supplies the underside (inferior wall) and backside (posterior wall) of the left ventricle.

What are collateral coronary arteries?

The coronary arteries also include the collateral coronary arteries. These are small blood vessels that connect the normal coronary arteries with one another.

When the heart is healthy, these vessels play only a minor role. But when a coronary artery becomes blocked, collateral coronary arteries help increase the flow of blood to the area of the heart that is being deprived of blood flow. These vessels are small. But they may actually succeed in providing enough blood to help prevent major damage to the heart muscle during a heart attack.

Why are they so important?

When the heart doesn't get enough oxygen-rich blood through the coronary arteries, the affected heart muscle can weaken or die. This is what happens during a heart attack. The damaged heart muscle can't pump effectively, which can lead to heart failure.