37. Cardiac rhythm and conduction disturbances in childhood.

Question 1

Sinus arrhythmia

Answer 1

normal variation

associated with breathing:

HR increases on inspiration and decreases on expiration

Question 2

Etiologies of Dysrhythmias in childhood

Answer 2

• Drugs
• Infectious/Postinfectious:
  
  • Myocarditis
  • Lyme
  • Endocarditis
  • Diphteria
  • Guillan Barré
  • Rheumatic fever
• Metabolic endocrine:
  
  • Electrolyte distrubances
  • Cardiomyopathy
  • Thyrotoxicosis
  • Uremia
  • Pophyria
  • Peochromozytoma
• Structural lesions
  
  • CHD
  • Ventricular tumor

Question 3

Atrial Dysrhythmias

Wandering Atrial Pacemaker

Answer 3

change in P-wave morphology with variable PR-interval and normal QRS

benign finding

requires no further evaluation or treatment

Question 4

Premature Atrial Contractions

Answer 4

common prenatally and in infants

premature P-wave

usually with an abnormal axis, consistent with its ectopic origin

usually benign

Question 5

Atrial Flutter and Atrial Fibrillation

Answer 5

uncommon

usually after surgical repair of complex CHD

maybe in myocarditis or drug toxicity

Question 6

Supraventricular Tachykardia

Answer 6

• most common symptomatic dyrhythmia
• rapid, regular HR, narrrow QRS
• often 280-300 bpm
• usually asymptomatic in the otherwise healthy
• Treatment:
  
  • depends on presentation and symptoms
  • acute in infants ► vagal maneuvers
  • IV-adenosine to convert
  • synchronized cardioversion

Question 7

Premature Ventricular Contractions

Answer 7

less common than premature atrial contractions in infancy and more common in older children

beat not preceded by P-wave

QRS is wide and bizarre

usually benign and require no treatment

Question 8

Ventricular Tachykardia

Answer 8

3 or more continuous PVCs

relatively rare, usually a sign of serious disease/dysfuncion

may require cardioversion

Question 9

Heart Block

Answer 9

• 1st degree:
  
  • Prolongued PR-Interval
  • asymptomatic and not treated
• 2nd degree:
  
  • some, but not all P-waves are followed by QRS
• Mobitz I (Wenckebach)
  
  • continuous prolongation of PR
• Mobitz II
  
  • PR doesn’t change
  • QRS is intermittedly dropped
• 3rd degree
  
  • no relationship between atrial and ventricular activity