cardiac arrhythmias

sinus arrhythmia
1. normal in kids
2. detected as cyclical change in heart rate w/ respiration
  1. acceleration during inspiration & slowing on expiration
    1. heart rate changes by up to 30 beats/min
supraventricular tachycardia
1. commonest childhood arrhythmia
2. rapid heart rate
  1. 250-300 beats per min
3. ->
  1. poor cardiac output
  2. pulmonary oedema
4. presents w/ sx of heart failure in neonate or young infant
  1. often ppted by febrile illness
  2. sudden onset & cessation
    1. lasts seconds to hours
5. can cause
  1. hydrops fetalis
  2. intrauterine death
6. re-entry tachycardia
  1. circuit of conduction set up
    1. w/ premature activation of atrium via an accessary pathway
  2. rarely structural prob is origin
    1. but must do echo
7. Ix
  1. ECG
    1. narrow complex tachycardia
      1. of 250-300 beats per min
    2. may see P wave after QRS complex
      1. due to retrograde activation of atrium via accessory pathway
    3. if severe heart failure
      1. changes suggestive of myocardial ischaemia may be seen
        T wave inversion in lateral precordial leads
    4. when in sinus rhythm
      1. short P-R interval may be detected
        Wolf Parkinson White syn
        short P-R interval & delta wave
        to early antegrade activation of ventricle via the pathway
        pre-excitation sn predisposing to SVT
        due to abnormal re-entry circuit btw AVN & accessory pathway connecting atrium to ventricle
        within interventricular septum or on right or left lateral cardiac border
        assoc w/
        Ebstein's anomaly
        post surgical repair
        cardiomyopathy
8. Mx
  1. aim= prompt restoration of sinus rhythm
    1. circulatory & respiratory support
      1. correct tissue acidosis
      2. +ve Pa ventilation if needed
    2. vagal stimulation manoeuvres
      1. carotid massage
      2. cold ice pack to face
      3. works in 80% of cases
    3. iv adenosine
      1. Rx ofchoice
      2. safe & effective
      3. induces AV block after rapid bolus injection
        ends tachycardia by breaking re-entry circuit set up btw AVN & accessory pathway
      4. given incrementally in increasing doses
    4. if adenosine fails
      1. electrical cardioversion w/ a synchronised shock
        0.5-2J.kg body weight
  2. once sinus rhythm restored
    1. maintenance needed
      1. flecainide
      2. sotalol
      3. digoxin
        used alone when no pre-excitation wave (delta wave) on ECG
        + propanolol
        if delta wave present on ECG
  3. Rx stopped at 1 year old
    1. 90% of kids have no further attacks after infancy
      1. but ECG remains abnormal
  4. WPW syn
    1. quick assessment
      1. to ensure can't conduct quickly
      2. w/ atrial pacing
        in teens
        reduce chance of sudden death
  5. (risk of) relapse
    1. target accessory pathway
      1. radiofreq ablation
      2. cryoablation
congenital complete heart block
1. rare
2. related to presence of anti-Ro/anti-La antibodies in maternal serum
  1. these mums will have manifest/latent connective tissue disorders
    1. subseq pregnancies affected
  2. prevents normal development of electrical conduction sys in developing heart
    1. atrophy & fibrosis of AVN
3. can cause
  1. fetal hydrops
  2. death in utero
  3. neonatal heart failure
4. most are asymp for many years
5. can be symptomatic
  1. presyncope
  2. syncope
  3. if so need endocardial pacemaker
other arrhythmias
1. long QT syn
  1. sudden loss of consciousness
    1. during
      1. exercise
      2. stress
      3. emotion
  2. differential
    1. epilepsy
  3. usually in late childhood
  4. if unrecognised
    1. sudden death from ventricular tachycardia can occur
  5. autosomal dominant inheritance
  6. assoc w/
    1. erythromycin therapy
    2. electrolyte disorders
    3. head injury
  7. part of channelopathies
    1. caused by specific gene mutations
    2. abnormalities of Na+, K+ or Ca2+ channels -> gain/loss of function
  8. assess anyone w/
    1. fam hx of sudden unexplained death
    2. hx of syncope on exertion
2. rare
  1. often seen in kids who've had surgery for complex congenital heart disease
    1. atrial fibrillation
    2. atrial flutter
    3. ectopic atrial tachycardia
    4. ventricular tachycardia
    5. ventricular fibrillation

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cardiac arrhythmias

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	Created by v.djabatey about 10 years ago