Tachycardia is a common type of arrhythmia (abnormal heartbeat) that occurs when the heart beats too fast while at rest. An adult's heart usually beats between 60 and 100 times per minute at rest. Tachycardia is a heart rate over 100 beats per minute. In infants and toddlers, tachycardia presents as a resting heart rate of at least 150 beats per minute. There are several types of tachycardia. In some cases, tachycardia doesn't cause any complications. In other cases, however, untreated tachycardia can cause serious complications, such as stroke, heart failure, or death.
The heart is made up of four chambers: two on top, the atria, and two lower chambers or ventricles. The sinus node in the right atrium controls the heart, acting as a natural pacemaker. The sinus node produces electrical impulses that begin each heartbeat. An electrical impulse travels from the sinus node across the atria, which results in the atrial muscles contracting and pumping blood into the ventricles. The electrical impulse arrives at a cluster of cells known as the atrioventricular (AV) node. The AV node slows down the electrical impulse before sending it on to the ventricles, to allow the ventricles to fill with blood. When an electrical impulse reaches the ventricular muscles, the muscles contract, pumping blood to the lungs and the rest of the body. When something disturbs this electrical system, tachycardia can occur.
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