Neonatal Supraventricular Tachycardia - Causes, Symptoms, and Management

Introduction

Normal heartbeat can be slow or fast depending on the activity; for example, if at rest, the heartbeat slows down, and if excited, the heart beats faster. But sometimes, even at rest, the heartbeat of young children is abnormally fast, which is caused by abnormal heart tissue in heart ventricles, which will eventually cause an irregular electrical activity of the heart. Approximately affecting one in 750 children or young pediatric patients. Heartbeat can race to 300 beats per minute and lead to unconsciousness. It may happen at any age. Neonatal SVT is not life-threatening today; it has a 99 percent chance of curing permanently due to various technologies available.

What Is Neonatal Supraventricular Tachycardia (SVT)?

Neonatal SVT is an irregular, rapid heartbeat that results in the inadequate filling of the heart ventricles. SVT is any tachycardia caused by bifurcation of His bundle (HB) and anyone supraventricular structure, including the atrial myocardium, the atrioventricular node, the proximal HB, the coronary sinus, the pulmonary veins, the vena cava or bypass tracts other than HB. Other forms of SVT include atrial tachycardia, atrial flutter, and re-entry near AV (atrioventricular) nodes.

What Are the Causes of Neonatal SVT?

It is caused by an accessory electrical pathway (an additional electrical connection between the top and bottom chambers of the heart). It causes a short circuit and pumps the blood less effectively. Most common in newborns. The SVT can develop before birth, in the womb. If it occurs in the womb, there will be fluid buildup in the body of the baby which can prove fatal. SVT occurs after birth in various episodes, which can last from a few seconds to hours. There is no obvious reason for triggering these episodes.

What Are the Signs and Symptoms of SVT?

In infants, it is very important to diagnose as infants cannot speak or tell the problem.

• The heartbeat is very fast or tachypnea.

• Heart flutters, heart palpitations (heart sensations) are uncomfortable and caused by a rapid heartbeat.

• Pain in chest.

• The baby looks pale or ill.

• Dizziness.

• Fatigue.

• Baby sweats a lot while feeding.

• Shortness of breath.

• Fainting or collapsing (it is not a common symptom).

• Poor feeding.

• Vomiting.

• A general decrease in the baby's attention span.

In toddlers, the symptoms will include:

Toddlers will be able to communicate the problem they will be facing.

• Heart pounds.

• A heartbeat can be heard in the throat.

• Heart beeping in the chest.

• Fast or irregular heartbeat.

If the episode lasts more than 24 hours or if one episode is longer than 20 minutes, seek medical help. Failing to seek medical help can lead to heart failure. Patients with SVT usually do not have any manifestations when they do not have these attacks.

How to Diagnose SVT?

• Electrocardiogram (ECG or EKG): It records the heart's electrical activity. It is a type of ultrasound that takes hold of the moving images of the heart. ECG should not be performed after any tachycardia event, and it is important to perform it while the child has tachycardia symptoms.

• Holter Monitor: It is the heart monitor to monitor the heart continuously for 24 hours.

• Event Monitor: It is a special monitor that can be worn for 30 days; it allows the child to self-record the symptoms by pressing a button. After 30 days, it can be analyzed by a cardiologist.

• X-ray.

• Physical examination.

• Blood test.

What Is the Treatment for SVT?

• Self-Limiting: Supraventricular tachycardia episodes usually are self-limiting. Many infants with SVT will outgrow the arrhythmia by the time they are 12 months or one year old.

• Self-Treatments: Older children exhibiting the symptoms can learn to do these self-treatments to slow or stop the fast heartbeat.

  • Vagal Maneuvers: Holding a breath and directing it down (valsalva maneuver), for example, blowing through the straw, pretending to have a bowel movement.

  • Immersing face in ice-cold water (diving reflex).

  • Doing a headstand.

  • To cough.

  • To put a finger down through the throat as done to vomit (vomit reflex).

• Medications: Medicines do not cure SVT but can reduce the number of episodes and control them. Beta-blockers or anti-arrhythmic medication can be prescribed.

• Ablation: It is a catheter ablation procedure to eliminate SVT permanently. The procedure is to place a large IV (intravenous catheter) in the large blood vessels in the leg. The catheter is further progressed till the heart veins. The catheter will transmit the electrical impulses or signal, which helps identify the extra electrical connection; further, it can be destroyed or eliminated permanently. The time taken by this procedure is several hours. Children under this procedure can be sent home on the same day. The children should experience no symptoms after ablation.

• Radio Ablation: It burns the area of abnormal heart tissue, causing impaired signals. Effective in 95 percent of the cases

• Cryoablation: It freezes the affected area causing abnormal heart rhythms. Effective treatment in 80 percent of the cases.

• Electrical Cardioversion Treatment: The child will be given short-acting anesthesia. A nurse will place the electrodes (connected to a defibrillator) on the child's chest. Further controlled shock is given to the child on the chest wall. This is done to set the abnormal heart rhythm to normal. The time taken is usually ten minutes without any complications. It is an intermediate procedure as it does not cure SVT. If the abnormal heart rhythm comes back, the procedure will be repeated.

• Monitoring At Home: For infants, the parents will be advised to monitor them at home. Parents and kids can detect a fast heartbeat if a child exhibits certain symptoms, such as poor feeding or eating habits, fatigue, increased irritability compared to other days, profuse sweating, a fast heartbeat, or dizziness. Parents will be advised to place one hand on the baby's chest and monitor these symptoms.

• Follow-Ups: Follow-ups should be followed twice or once yearly, as per the cardiologist's advice.

How Can Parents Deal With Neonatal SVT?

Getting the diagnosis for a child with Neonatal SVT is overwhelming for parents, but most children with SVT have a normal life. However, it is important to meet the child's physician or cardiologist for advice on SVT. Also, keep the doctor's phone number handy in any emergency. Whenever possible, write down all the questions that need to be answered by the doctor. Preplan the visit accordingly.

Conclusion

Most children with SVT have entirely normal lives and normal life expectancies. Catheter ablation requires no follow-up for older children. Correct diagnosis at a young age is important for healthy outcomes.