When the heart rate is generally faster than normal, this condition is defined as tachycardia. It is a potentially life-threatening event, as it can affect perfusion by compromising the heart’s ability to perform well. There is a shorter relaxation phrase when the heart beats rapidly, which leads to problems such as the ventricles being unable to fill completely, such that cardiac output is much lower; and less blood being transported to the coronary arteries, which means blood supply to the heart is decreased.
Different kinds of tachycardia are hard to differentiate in pediatric cases when monitoring the patient with ECG because of the child’s faster heart rate.
Signs and Symptoms of Tachycardia
- Quickened and weakened pulse
- Pulmonary edema/ingestion
- Different mental state
- Respiratory distress/failure
- Poor tissue perfusion (e.g., abnormal urine output)
- Occurs usually during fever or stress
- Usually not life-threatening
- Fast rate but with normal rhythm
- Rhythm begins above ventricles
- Leads to abnormal heart rhythm
- ECG presents this as a sawtooth pattern
- Rhythm begins in the ventricles
Cases of tachyarrhythmias in children and infants are divided into narrow complex or wide complex tachycardia. The QRS complex on the ECG can be measured to study its width.
|NARROW QRS COMPLEX
(≤ 0.09 s)
|WIDE QRS COMPLEX
(> 0.09 s)
|Atrial fibrillation or Atrial flutter
|Supraventricular Tachycardia (SVT)
Narrow QRS Complex
Atrial flutter is a rare, abnormal rhythm perceivable through a sawtooth pattern on an ECG. An abnormal pathway forces the atria to beat rapidly and inefficiently. Though some contractions may exceed 300 bpm, not all will lead to ventricular contraction, as not all will reach the AV node.
PALS providers usually need to determine the difference between identical narrow QRS complex tachyarrhythmias: supraventricular tachycardia (SVT) and sinus tachycardia. SVT is usually caused by accessory pathway reenter, whereas AV node is commonly caused by reentry and ectopic atrial focus.
|Infant: < 220 bpm
|Infant: > 220 bpm
|Child: < 180 bpm
|Child: > 180 bpm
|Varies with stimulation
|Constant, fast rate
|Visible P waves
|Absent P waves
Wide QRS Complex
Though a rare case in the pediatric age group, ventricular tachycardia (VT) can be hazardous. Until proven otherwise, an ECG reporting a QRS complex greater than 0.09 seconds is believed to be a VT. It is important to note that there are ways to reverse tachycardia as long as treatment for VT is not delayed in cases such as polymorphic VT, Torsades de Pointes, and unusual SVT, as they can easily regress to ventricular fibrillation (VF).
As it is usually above 120 bpm, VT is not considered to be an abnormally fast rate and is actually fairly standard. During VT, P waves are either lost or dissociated from the QRS complex. When a supraventricular and ventricular impulse converge, this reaction yields a hybrid-appearing QRS or fusion beat.