During an arrhythmia, the heart may not be able to pump enough blood to the body. Lack of blood flow can damage the brain, heart, and other organs. Arrhythmias can also occur with rapid heart rates (called tachyarrhythmias -- faster than 100 beats per.
A normal heart rate is 50 to 100 beats per minute. Arrhythmia and abnormal heart rates don't necessarily occur together. Most arrhythmias are harmless, but some can be serious or even life threatening.