What is Tachycardia?

In this lesson, we're going to cover tachycardia, including some things to be aware of when dealing with tachycardic pediatric patients, types of tachycardia, underlying causes, and some information on the best courses of treatment to resolve that patient's tachycardia.

When an infant or child's heart rate is greater than normal for their age, activity level, and clinical condition, that patient is considered tachycardic.

Types of Tachycardia

Common types of tachycardia include:

• Atrial fibrillation
• Atrial flutter
• Sinus tachycardia
• Supraventricular tachycardia (SVT)
• Ventricular tachycardia
• Ventricular fibrillation

Causes of Tachycardia

Many things can cause tachycardia, including semi-benign causes such as fever or stress. More serious causes of tachycardia include:

• Shock
• Medications
• Metabolic dysfunction
• Hypoxemia
• Damage to the heart muscle

Perfusion problems may develop when the patient's heart beats too fast and the ventricles are not able to fill properly with blood. This can cause a decrease in cardiac output and poor perfusion, which can lead to hemodynamic instability.

Identifying and Treating Tachycardia

It's important to treat the underlying cause first when dealing with a tachycardic pediatric patient. Important steps in caring for an infant or child with tachycardia are:

1. Maintain a patent airway and provide adequate oxygenation. Your goal is to maintain an oxygen saturation of at least 94 percent.
2. After that, you'll want to get a cardiac monitor attached to the patient to correctly evaluate what the underlying rhythm is and if you can, obtain a 12-lead ECG.

However, as stated in the last lesson, do not delay treatment while trying to obtain a 12-lead.

There are some helpful signs to aid you in identifying the type of tachycardia seen on the ECG.

First, determine if the QRS is wide or narrow. A narrow/normal QRS for pediatric patients is 0.9 seconds or less.

Before we distinguish the different rates for SVT vs. sinus tachycardia, it's important to note that the main difference between the two is that sinus tachycardia (though difficult to see on an ECG) will have P-waves, while SVT does not.

Therefore, SVT is more unstable and the rate with sinus tachycardia can sometimes change with activity. Having said that, if the patient has a normal QRS, you'll still need to determine whether that patient has sinus tachycardia or SVT.

Sinus Tachycardia

Sinus tachycardia for an infant is usually a heart rate of less than 220 beats per minute. While sinus tachycardia for a child is typically a heart rate of less than 180 beats per minute.

It's important to note that a patient's history will usually be consistent with the cause of their tachycardia.

With sinus tachycardia, P-waves are present and normal and the QRS is also normal. And the heart rate will vary with the patient's level of activity.

Usually, sinus tachycardia does not require treatment. Instead, it's important to search for, and treat for, the cause of the tachycardia.

Supraventricular Tachycardia (SVT)

SVT for an infant is usually a heart rate of greater than 220 beats per minute. While sinus tachycardia for a child is typically a heart rate of greater than 180 beats per minute.

With SVT, QRS is normal but P-waves are usually absent. Patient history will usually reveal an abrupt change in heart rate. Alternatively, it can also be ambiguous as to what caused the change. And heart rate does not vary with the level of activity.

Regarding treatment for patients with regular narrow complex stable tachycardia, it's appropriate to first attempt vagal maneuvers. With children, have them attempt to blow through a narrow straw. With infants, place a bag of ice over the upper half of their face, making certain to not obstruct the airway.

Medications and Treatment for Tachycardia

If vagal maneuvers don't work, it may be time to consider medications, specifically adenosine at .1mg/kg via rapid IV push, followed with a 20cc bolus of normal saline to expediate the medication delivery.

If the patient doesn't convert and remains stable, a second dose can be given at .2mg/kg, again via rapid IV push, and again, chase the treatment with a 20cc bolus of normal saline.

For stable patients with an ECG rhythm that shows irregular narrow complex QRS tachycardia – while unusual – could be atrial fibrillation, atrial flutter, or multi-focal atrial tachycardia.

Often, antiarrhythmics are used to treat wide complex stable tachycardias, such as procainamide or amiodarone. However, the management and treatment of wide complex stable tachycardias requires advanced knowledge of ECG rhythm interpretation and antiarrhythmic therapy.

If a child is experiencing SVT or wide complex tachycardia and remains stable and doesn't respond to medication therapy, consult with a pediatric cardiologist before proceeding with synchronized cardioversion.

For a child with unstable tachycardia, such as a child with hypotension, synchronized cardioversion would be the appropriate first choice. Sedation, if needed and if time allows, would also be appropriate. But don't delay cardioversion that's required to stabilize a patient.

Cardioversion for Tachycardia

For a child with unstable tachycardia, start with an energy dose of .5 to 1 joules/kg. If the initial dose is ineffective, increase the electrical dose to 2 joules/kg.

Make sure to record and monitor the ECG before, during, and after each cardioversion attempt. And after cardioversion has been successful, obtain a 12-lead ECG, then pass this patient on to the appropriate next stage of treatment.