Supraventricular Tachycardia (SVT)
Normally, the chambers of the heart (atria and ventricles) contract in a coordinated manner. The contractions are caused by an electrical signal that begins in an area of the heart called the Sino atrial node (also called the sinus node). The signal moves through the upper heart chambers and tells the atria to contract. The sinus node is a natural pacemaker that controls the rhythm of the heart. Electrical impulses travel from the natural pacemaker through the atria then pass through a filter before running down specialized fibers that activate the ventricles. The atria are above the ventricles, thus the term supraventricular. The term tachycardia refers to a rapid heartbeat of over 100 beats per minute. Supraventricular tachycardia then is a rapid rhythm of the heart that begins in the upper chambers. When patients experience change in the normal sequence of electrical impulses and an abnormal heart rhythm occurs, they are having an arrhythmia.
SVT means that from time to time your heart beats very fast for a reason other than exercise, high fever, or stress. During an episode of SVT, the heart’s electrical system doesn’t work right, causing the heart to beat very fast. The heart beats at least 100 beats per minute and may reach 300 beats per minute. After treatment or on its own, the heart usually returns to a normal rate of 60 to 100 beats per minute. SVT may start and end quickly, and you may not have symptoms. SVT becomes a problem when it happens often, lasts a long time, or causes symptoms.
Most episodes of SVT are caused by faulty electrical connections in the heart. What causes the electrical problem is not clear. SVT also can be caused by certain medicines. Examples include very high levels of the heart medicine digoxin or the lung medicine theophylline. Some types of SVT may run in families. Or they may be caused by a lung problem such as COPD or pneumonia. The condition most occurs in young people or infants...
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