definition cardiac dysrhythmias
An irregular heartbeat is an arrhythmia (also called dysrhythmia). Heart rates can also be irregular. A normal heart rate is 50 to 100 beats per minute. Arrhythmias and abnormal heart rates don't necessarily occur together. Arrhythmias can occur with a normal heart rate, or with heart rates that are slow (called bradyarrhythmias -- less than 50 beats per minute). Arrhythmias can also occur with rapid heart rates (called tachyarrhythmias -- faster than 100 beats per minute).