Dysrhythmias, presentation
also see Heart Blocks

Asymptomatic with irregular rhythm on exam

• Palpitations
• Chest pain
• Dizziness
• Syncope
• Sudden death

Sinus Arrythmia

• Most common irregularity
• Normal variant
• Increases rate with Inspiration, decreases with expiration

Premature Atrial Contractions

• Benign and usually asymptomatic
• More common in the newborn period and tend to disappear in frequency as the child grows older
• ECG:
  • The ectopic P wave has a different appearance
  • The extra P wave may yield a normal QRS, a widened QRS (aberrant pathway) or not conduct (“blocked PAC”)

Premature Ventricular Contractions

• Can present with palpitations
• More frequent in older children and adolescents
• Benign PVC’s are single, unifocal in origin (all look the same) and disappear with exercise
• ECG:
  • Wide QRS
  • Compensatory pause follows the premature ventricular beat because of refractory ventricles
• Causes:
  • Catheters, hypoxia, electrolyte abnormalities, drugs, and structural defects
• Criteria for work-up
  • Three in a row
  • Multifocal origin (PVC’s look different)
  • Increases with exercise
  • Underlying heart disease

Sinus Tachycardia

• Rapid HR originating from the SA node
• ECG:
  • HR usually < 200 bpm
  • Normal P waves axis and QRS
  • Variable beat-to-beat HR
• Causes:
  • Fever, catecholamine release, thyrotoxicosis
  • Treat the underlying problem

Supraventricular Tachycardia

• Most common abnormal rapid rhythm in pediatrics
• Peak incidence
  • 1st 3 months (present in failure): majority resolve by 12 mos of age
  • > 8 years of age: usually do not resolve spontaneously
• Symptoms:
  • Rapid rate starts and stops suddenly
  • “racing or pounding” heart beat
  • If tachycardia persist > lethargy, pallor > CHF
  • ECG findings:
    • HR>220 beats/min, very regular rate
    • Narrow regular QRS
    • Regular rhythm
    • Retrograde P waves, normal P waves, absent P waves
• Causes
  • In children < 12 y/o, caused by an accessory AV connection
  • 25% of patients with SVT will show WPW on post-conversion ECG
  • In teenage years, AV nodal reentry tachycardia is also animportant cause
  • Unoperated congenital heart disease (Epstein’s anomaly)
• Treatment:
  • Vagal maneuvers (dive reflex, valsalva, carotid massage, rectal stim)
  • Adenosine (rapid infusion with NS flush): Have defibrillator ready, as adenosine may cause atrial fibrillation
  • Verapamil(contraindicatedin <1yr)
  • Synchronized DC cardioversion if unstable(0.5-1 J/kg)

Wolf Parkinson White Syndrome

• Bundle of Kent
• Occurs in 25% of patients with SVT
• ECG: short PR, delta-wave, prolonged QRS
• The risk for sudden cardiac death is 1% every 10 years
• Avoid digoxin (proarrythmic)
• Catheter ablation successful in 85-95%
• B-blocker to prevent further attacks
• Digoxin
  • is a relative contraindication in patients with pre-excitation SVT (WPW)
  • Digoxin tends to stimulate the alternative-pathway which can cause atrial flutter and fibrillation to progress to ventricular flutter and fibrillation
  • usually ok to use in the first year of life

Atrial flutter

• Atrial rate: fixed, > 350 beats/min (atrial 220-430 bpm, ventricular <300 bpm)
• Rhythm is regular or variable
• Atrial flutter is usually the result of a single re-entrant circuit in the right atrium
• ECG:
  • saw-tooth pattern
  • Ventricular rate is fixed (may be variable AV conduction)
  • QRS narrow (<0.12)
• Treatment:
  • Digoxin for preventing increased ventricular rate
  • Cardioversion

Atrial fibrillation

• Atrial rate: indeterminable (atrial 350-650 bpm, ventricular rate: slow to rapid)
• Atrial fibrillation is the result of multiple “wavelets” of depolarization moving around the atria chaotically, rarely completing a re-entrant circuit.
• Rhythm: Irregularly-irregular heart rate
• ECG:
  • P waves are atypical and amorphous, fibrillatory - fine or coarse
  • Ventricular response rate is variable; narrow QRS
• Treatment: DC cardioversion

Ventricular Tachycardia

• Defined as three or more continuous wide QRS complexes with abnormal or absent P waves
• Symptoms
  • Hemodynamic instability, shock
  • may need no treatment if slow rate and hemodynamically stable
• ECG:
  • The rate varies between 120-250 best/min
  • Wide QRS
  • AV dissociation
• Uncommon and majority have underlying congenital or acquired heart disease
• Associated with:
  • Open heart surgery for Tetrology of Fallot, VSD
  • Myocarditis, myocardial tumor
  • Electrolyte imbalance, drugs (TCA)
• Treatment
  • Amiodarone, or
  • Procainamide, or
  • Lidocaine
  • Requires immediate cardioversiononly if unstable (poor perfusion)

Long QT Syndrome (QT (corrected))

Electrolytes Abnormalities:

• HyperCa: short QT
• HypoCa: prolonged QT

Hyperkalemia

Hypokalemia

• flat T, U-wave

Note on verapamil:

Verapamil

• Calcium channel blocker
• contraindicated in children <1 y/o
• In infants, they do not have active calcium pumps and they depend on their calcium channels for their cardiac muscle to work.
• Calcium channel blockers are associated with sudden death in children

CHLA Board Review 2005