Hi,
An irregular heartbeat is an arrhythmia which can occur with a normal heart rate, or with heart rates that are fast or slow. If the heart rate is irregular, this may be due to coronary artery disease, electrolyte imbalances, changes in the heart muscle, injury from a heart attack or as part of a healing process. Are there other symptoms present? It would be best to have this evaluated by your doctor or cardiologist to determine the cause.
Take care and regards.
An arrythmia can be defined as a heart rate that does not beat in the typical "lub-dub" pattern. Many, many times arrythmias are benign, but it's always best to listen to your doctor and follow through on suggested tests, medications and recommendations.
Tachycardia is when the heart rate exceeds 100 beats per minute.