Coronary artery disease is one of the causes of a condition called atrial fibrillation.

It is serious problem that causes a fast, irregular heart rhythm.

Dr. Jeffrey Snyder, a cardiologist with Lehigh Valley Health Network, first explained how the heart works and then atrial fibrillation.

The heart has four chambers: two upper chambers and two bottom chambers. Oxygen-poor blood comes into the upper chamber on the right side and the chamber pushes the blood into the bottom chamber, which pushes the blood to the lungs to get oxygenated. Oxygen-rich blood comes back to the heart from the lungs to the heart’s upper chamber on the left side. That chamber pushes the blood into the lower chamber on the left, which pushes the blood into an artery and out to the veins.

With atrial fibrillation, the upper chambers sort of short circuit and quiver instead of producing a regular pump. There is a group of cells in the upper right chamber called the sinus node. It is the heart’s natural pacemaker. The movement of the signal through the two upper chambers causes the heart to squeeze and pump blood through the heart.

When blood isn’t completely squeezed into the lower chamber, it can pool in the upper chamber and become a clot, Snyder said. If a clot becomes dislodged, it can go to the brain and cause a stroke. Atrial fibrillation can also cause heart failure and other heart-related problems.

High blood pressure and age are two of the biggest factors leading to A-fib. Snyder said that 10% of the people over the age of 70 will develop atrial fibrillation, and 15% over the age of 80.

Treatment is evolving and improving, he said.