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Chapter 4 : Bradyarrhythmias And Tachyarrhythmias

Cardiac dysrhythmia or arrhythmias are caused by abnormalities in the electrical activity of the heart and can be classified as bradyarrhythmias, tachyarrhythmias or pulseless arrest.

Bradyarrhythmias


Bradyarrhythmias are the most common arrhythmias in children and usually presents with hypoxemia, hypotension and acidosis. Bradycardia is a heart rate which is slower than the normal for the age of the child; usually less than 60 bpm is indicative of bradycardia and immediate CPR should be initiated.

Signs of Bradycardia
  • Poor end-organ perfusion
  • Shock with hypotension
  • Sudden collapse
  • Altered consciousness
Symptoms of Bradycardia
  • Change in level of consciousness
  • Dizziness
  • Lightheadedness
  • Fatigue, syncope

There are 5 examples of bradyarrthmias that are seen in children:

  • Sinus node arrest/sick sinus syndrome
  • Sinus bradycardia
  • First-degree AV block
  • Second-degree AV block: Type I (Mobitz 1) and Type II (Mobitz II)
  • Third-degree AV block
Sinus Node Arrest/Sick Sinus Syndrome

Sinus node arrest/sick sinus syndrome is associated with abnormal heart rhythms due to malfunction of the sinus node. These may include atrial, junctional and idioventricular escape rhythms.

Sinus Bradycardia

Sinus bradycardia starts in the SA node with decreased rate (<60 beats/min). It develops due to decreased metabolic demand and may be caused by hypoxia, poisoning, hypoglycemia, or hypothyroidism.

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First Degree AV Block

First degree AV block is when the PR interval is prolonged (> 0.20 seconds) and impulse from atria to ventricles through the AV node is delayed. There usually are no symptoms associated with first-degree AV block.

Second Degree AV Block Type I

2nd Degree AV block type I (Wenckebach-Mobitz I) is when the PR intervals are prolonged, R-R intervals are shortened and finally one beat drops. Symptoms may include dizziness, but usually not seen.

Second Degree AV Block Type II

2nd degree AV block Type II (Mobitz II) is when there is no change in the PR interval and then a beat will drop randomly. Symptoms may include irregular heart bear, presyncope or syncope.

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Third Degree AV Block

3rd degree Av block is a complete heart block where the P wave and QRS complexes are not connected. Impulse conducted in the atrium does not progress to the ventricles. There is no communication between the atrium and the ventricles. Symptoms include fatigue, presyncope or syncope.

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Management of Bradyarrhythmias

Proper management of bradyarrhythmia includes managing for heart rate and respiratory distress or failure. The following are steps in the treatment of bradycardia:

  • Upon recognizing the child is bradycardic immediately activating the EMS and conducting the ABCs
    • Open and support the airway
    • Give oxygen and/or ventilation
    • Start chest compressions with 100/min
    • Attach a defibrillator for children over 1 years old
    • Obtain a 12-lead ECG
    • Get vascular access
    • Get labs
  • If bradycardia is still persistent continue performing CPR
  • After one round of CPR give the following doses of medications:
    • Epinephrine: IV/IO 0.01 mg/kg and repeat every 3 to 5 minutes
    • Give atropine as fist dose of 0.02 mg/kg if there is increased vagal tone or primary AV block
  • Continue the process till child’s rhythm is back to normal and consider the Hs and Ts
  • Consider cardiac pacing
  • The following shows management of bradycardia in children:

pediatric-bradycardia

 

Tachyarrhythmias

Tachyarrhythmias are considered fast abnormal rhythms, which originate from the atria or ventricles. Tachycardia is a heart rate which is faster than the normal for the age of the child; and immediate CPR should be initiated.

Signs of Tachycardia
  • Sudden collapse
  • Respiratory distress or failure due to pulmonary edema
  • Shock with hypotension or poor end-organ perfusion
  • Altered consciousness
Symptoms of Tachycardia
  • Palpitations
  • Dizziness
  • Lightheadedness
  • Fatigue, syncope

The following are examples of tachycardia:

  • Atrial flutter
  • Sinus tachycardia
  • Supraventricular Tachycardia (SVT)
  • Ventricular tachycardia (VT)
  • Polymorphic VT/Torsades de pointes
Atrial Flutter

Atrial flutter is abnormal heart rhythm causing fast irregular heartbeat. Usually occurs in the atria of the heart and is uncommon in children. Some causes of atrial flutter include: hypertension, ischemia, cardiomyopathy, and abnormal heart valve.

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Sinus Tachycardia

Sinus tachycardia is when the rate of impulse from the SA node is elevated than normal for age. Heart rate <220 bpm in infants, <180 bpm in children, P wave is normal, PR interval is constant, and R-R interval is variable. Some causes of ST include: hypoxia, hypovolemia, fever, poison, metabolic stress, trauma, pain, anxiety, toxicity, and anemia.

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SVT

Supraventricular Tachycardia (SVT) is a rapid heartbeat that starts right above the ventricles. SVT is the most common cause of tachyarrhythmia in infants causing cardiac issues. Heart rate >220 bpm in infants, >180bpm in children, p wave is abnormal; R-R interval is constant. Some causes of SVT include: AV nodal reentry, ectopic atrial focus, and accessory pathway entry.

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Ventricular Tachycardia (VT)

Ventricular tachycardia (VT) starts in the ventricles and is uncommon in children, and the heart rate is regular and at least 120 bpm. VT with pulse can cause the heart rate to exceed to 200 bpm and can go into VF or pulseless VT. In VT the P waves cannot be identified and T waves are opposite in polarity to QRS. Some causes of VT include: drug toxicity, prolonged QT syndrome, myocarditis, underlying heart disease, and electrolytes disturbances.

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Torsades de Pointes/Polymorphic VT

Polymorphic VT or Torsades de Pointes is when different areas in the ventricles fire fast, uncoordinated impulses. Ventricular rates range from 150-250 bpm and QRS complex vary in apprearance. Some causes of polymorphic VT or Torsades de pointes include: diarrhea, hypomagnesaemia, and hypokalemia.

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Management of Tachyarrhytmias

Upon recognizing the child with tachycardia immediately activating the EMS and conducting the ABCs

  • Open and support the airway
  • Give oxygen and/or ventilation
  • Start chest compressions with 100-120/min
  • Attach a defibrillator for children over 1 years old
  • Obtain a 12-lead ECG
  • Get vascular access
  • Get labs
  • Evaluate the QRS complex as either normal or wide
    • Normal = ≤0.08 sec
    • Wide = >0.08 sec
  • If normal QRS:
    • Could be ST = search for causes and treat the child for the specific symptoms
    • Could be SVT – consider vagal maneuvers, get vascular access and administer rapid bolus adenosine 0.1 mg/kg IV (max 1st dose of 6 mg), and can give second dose of 0.2 mg/kg IV (max 2nd dose of 12 mg)
  • If wide QRS:
    • Could be VT – treat reversible causes and administer the following drugs:
      1. Amiodarone 5 mg/kg IV over 20 to 60 minutes or procainamide 15 mg/kg IV over 30 to 60 minutes
      2. Can give adenosine 0.1 mg/kg IV only once (6 mg max dose)
  • Cardioversion can be attempted at 0.5 to 1 J/kg and obtain a 12-lead ECG

The following algorithms show management of tachycardia with a pulse and adequate perfusion and one with poor perfusion for children.

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