When the electrical loop is blocked anywhere along its route, normal heart rhythm can resume. The impulse then continues going around this circuit, somewhat like "a dog chasing its own tail" driving the heart at a very fast rate. However, if there is an early heart beat (called a premature atrial contraction - PAC, or premature ventricular contraction - PVC), the impulse may travel down to the lower chambers using the normal pathway, the AV node, causing the heart to beat, and travel back up the extra pathway to the atria. Most of the time, the extra pathway does not effect the heart rhythm. Usually the only electrical connection is the AV-node, so the extra connection provides a potential "short circuit" in the heart. When a child has SVT, there is usually an extra pathway (see the diagram below) in the heart's electrical system that connects the top chambers and lower chambers of the heart. The information in this section applies to children with WPW but there are a few differences discussed in that section. Wolff-Parkinson-White syndrome (WPW) is one subset of SVT and is the most common type of SVT in young children. Below is and example of an electrocardiogram (ECG) that was taken in an infant who had a heart rate of 280-300 beats per minute.Sometimes other names are used for SVT such as paroxysmal (starts and stops without warning) atrial tachycardia (PAT) and paroxysmal supraventricular tachycardia (PSVT). Supraventricular tachycardia means fast heart rate coming from the above the ventricles, in the heart's upper chambers (supra = above, ventricular = the lower heart chambers, tachy = fast, cardia = heart). When a child has SVT, the heart suddenly starts to beat very fast, at rates of 180 to 280 beats a minute and up to 300 beats a minute in infants. An arrhythmia is an abnormal heart rhythm caused by a problem in the heart's electrical system, also called the cardiac conduction system. Most of the time, the problem occurs in children with otherwise normal hearts but it can occur along with other congenital heart problems. While the problem is often congenital, meaning it is present at birth, the onset and severity of symptoms varies. It is said to occur in up to 1 in 2500 children. This reduces the amount of blood the heart pumps.Supraventricular tachycardia (SVT) is the most common arrhythmia (abnormal heart rhythm) diagnosed in children. Ventricular tachycardia: Electrical signals in the ventricles are activated many more times than normal.
Misfiring electrical signals cause the ventricles to quiver (beat chaotically fast) instead of to beat normally, making the heart unable to pump blood.
Ventricular fibrillation: This is the most serious type of arrhythmia and requires immediate care. Wolff-Parkinson-White syndrome is the main cause of supraventricular tachycardia in children. It’s the most common cause of an abnormally fast heartbeat. Supraventricular tachycardia: This disruption in electrical activity in the heart’s upper chambers o ften begins in the teen years. Sinus tachycardia: This is a normal increase in heart rate from exercise, fever or anxiety. It is rare in children and usually treated with medication.Ītrial flutter: T he heart’s upper chambers beat at a rapid and chaotic rate, making it harder for the heart to pump blood effectively.
This prevents blood from moving well into the lower chambers. Atrial fibrillation: The upper chambers beat at a rapid rate but in an organized way.
0 kommentar(er)
