The term arrhythmia refers to any change from the normal sequence of electrical impulses, causing abnormal heart rhythms. This can cause the heart to pump less effectively. Some arrhythmias are so brief (for example, a temporary pause or premature beat) that the overall heart rate or rhythm isn't greatly affected. But if arrhythmias last for some time, they may cause the heart rate to be too slow or too fast or the heart rhythm to be erratic.
The term tachycardia refers to a heart rate of more than 100 beats per minute. Bradycardia describes a rate of less than 60 beats per minute, a fast heart rate is called tachycardia. Tachycardias fall into two major categories. Ventricular tachycardia involves only the ventricles. Supraventricular tachycardia involves both the atria and the ventricles. The definition of too fast usually depends upon the person's age and physical activity
Rapid heart beating can be controlled with medications and by identifying or destroying the focus of rhythm disturbances.
A heart rate that's too slow is called bradycardia. What's too slow depends upon a person's age and physical activity.
A heart rhythm that's too slow can cause fatigue, dizziness, lightheadedness, fainting or near-fainting spells. These symptoms can be easily corrected by implanting an electronic pacemaker under the skin to speed up the heart rhythm as needed.