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Arrhythmias

Supraventricular Tachycardia

Supraventricular tachycardia or SVT is a very common form arrhythmia (abnormal rhythm) in children. It can affect children at any age. It may even start during fetal life.

Causes: SVT is not a uniform condition. The most common form of SVT is the so-called the reentry form (circulating electricity waves) as a result of a pathway (Figure 1). A pathway is a piece of muscle located around the tricuspid or mitral valve. A pathway creates the right condition to initiate and maintain a tachycardia. We call this form of SVT also ORT or orthodromic reentrant tachycardia. Another form of SVT is the AVNRT or atrioventricular nodal reentrant tachycardia (Figure 2). It is a reentry type of tachycardia, but usually at a slower rate. Another form of SVT involves areas of the upper chambers of the heart (the atria), where isolated cells beat faster the hearts natural rate (Figure 3). It is known as focal or ectopic atrial tachycardia.

Symptoms: Children usually complain about heart racing, heart “beeping”, dizziness or at times even chest pain. Infants who cannot verbalize their symptoms usually do not show any symptoms, at least not in the beginning. When the SVT continues for a while, they become irritable. Unrecognized tachycardia in infants may lead to more serious conditions including heart failure.

Diagnosis: The first clue is usually provided by the history. Physical examination is generally nonrevealing as the majority of children with SVT are otherwise healthy. The work-up always include  a baseline ECG or electrocardiogram. An echocardiogram may give us information about structural heart disease. To actually document the tachycardia patients are given a 24-hour or even a 30-day monitor.  These monitors can record the patient’s rhythm and give a visual confirmation to the physician.

Treatment: A treatment plan must be individually tailored. In the case of a patient with rare, brief episodes a treatment is usually not necessary. If the tachycardia is long lasting and/or frequent, then treatment is indicated. Patients ma choose to take medications that stabilize heart rhythm. These medicines do not cure the condition. Their aim is to hopefully prevent future recurrences. Such medications are not free of side effects. Another treatment options is called ablation (from the Latin word ablatio or taking away). In this procedures that to some extent resembles a cardiac catheterization, special catheters with metal tip are placed inside the heart. The operator can then find and burn or ablate the pathway of the focus of the Antipop Consortium Arrhythmia tachycardia with radiofrequency. Radiofrequency waves can generate heat in a small area of the heart and destroy the source of the tachycardia. Ablation is curative in most cases with rare complications.

 

 

 

Figure 1. An example of pathway induced SVT or ORT at a heart rate of 290 beats per minute.

 

 

 

 

Figure 2. An example of AVNRT. This patient had a heart rate of 182 beats per minute.

 

 

 

Figure 3. An example of ectopic atrial tachycardia. In this case the rhythm is irregular.

 

ELECTROPHYSIOLOGY BOARD REVIEW

 

Click here to view an excellent board review presentation about pediatric electrophysiology, prepared by Dr. Rahel Zubairi.

 

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