Dr. Mansfield
An arrhythmia is a problem with the rate or rhythm of the heartbeat. The problem may be a heart that beats too quickly, too slowly, or with an irregular rhythm. A heartbeat that is too fast is called tachycardia, and a heartbeat that is too slow is called bradycardia. Captain Miller, can you tell us more about arrhythmias?

Captain Miller
Of course, Dr. Mansfield. Most arrhythmias are harmless, but when arrhythmia keeps the heart from pumping enough blood to the body, it can be serious or even life-threatening.

Arrhythmias occur when there's a problem with the electrical signals that control the heartbeat. If the heart isn't receiving enough oxygen-rich blood due to plaque buildup in the coronary arteries, the heart's electrical system can become damaged. Electrical signals may be delayed or blocked, or they may originate in the wrong part of the heart.

For instance, in a type of arrhythmia called atrial fibrillation, or AFib, the heart's electrical signals don't begin in the sinoatrial, or SA, node as they would in a normal heart. Instead, the signals begin in another part of the atria or in the nearby pulmonary veins. In addition, the signals spread throughout the atria in a rapid, disorganized way, which causes the walls of the atria to quiver very fast instead of beating normally. As a result, the atria aren't able to pump blood into the ventricles the way they should. This can lead to blood pooling in the heart, which can cause blood clots to form. If a clot travels to the brain, it causes a stroke.

Another type of arrhythmia that can result from coronary artery disease is ventricular fibrillation, or v-fib. V-fib occurs if disorganized electrical signals make the ventricles quiver instead of pump normally. If the ventricles don't pump blood to the body, sudden cardiac arrest and death can occur within a few minutes.

Heart damage from coronary artery disease can also cause the heart to beat too slowly. If the heart rate is too slow, not enough blood reaches the brain, which can cause a person to pass out. Lack of blood flow can also lead to damage of other organs throughout the body.