Supraventricular Tachycardia

SVT

I am positive that everyone experienced some joyful palpitations on Valentine’s Day yesterday.  As our hearts raced with excitement, I am also sure that many of us considered ordering some adenosine… just in case.

While it has been fun pondering a variety of pediatric cardiovascular issues (like Kawasaki Disease, the 2010 Resus Update, Systolic BP Guide, use of PGE1, Syncope, Subtle signs of heart failure, Complications of fontans, Hypercyanotic spells, and Coarctation of the Aorta just to name a few), we should take a minute to discuss one of the most important cardiovascular issues in pediatrics.

Pediatric Supraventricular Tachycardia (SVT)

  • SVT is the most common symptomatic dysrhythmia in infants and children.
  • 3 types:
    • AV reentrant tachycardia
      • Has accessory pathway that bypasses the normal conjuction.
      • WPW with bundle of Kent is a classic example.
    • AV nodal / junctional tachycardia
      • Cyclical reentrant pattern due to dual AV node pathways.
    • Ectopic atrial tachycardia
      • A ectopic focus outpaces the SA node.
  • SVT in Infants
    • Commonly have nonspecific complaints of “fussiness” or “not acting right.”
    • Typically can tolerate SVT for 24 hours!
      • Those with congenital heart disease may not tolerate it as long as the loss of atrial kick and the short diastole will diminish their already poor cardiac output.
      • Eventually SVT will adversely affect even anatomically normal hearts.
        • Within 48 hours, 50% develop CHF.
  • SVT in older children
    • Rarely develop CHF from SVT, primarily because they are able to describe their symptoms.

     

Management

  1. ABC’s – naturally.
    1. Oxygen
      1. Important to use as the oxygen demand has increased… but…
      2. Recall that Oxygen is a medication and you should consider potential adverse reactions in those with congenital heart disease.
    2. Always ensure the patient in positioned to optimize and support the airway.
    3. Monitor!
      1. Get a rhythm strip pronto!
      2. Might actually need to speed up the pace of the paper to help distinguish any p-waves (particularly in the very young who can have sinus tach at 200 bpm).
    4. Access!!
      1. This is not the child that you want to allow every person in the ED to attempt an IV on.
      2. Call for your IO if you don’t have access after your first 2-3 attempts.
      3. While awaiting access, this is a perfect time to use some vagal maneuvers!
    5. UNstable SVT?
      1. Poor perfusion and/or severe heart failure should lead to Synchronized Cardioversion!
      2. Look for prolonged cap refill, lethargy, mottled skin, and hepatomegaly.
  2. Vagal Maneuvers
    1. Telling a child to “bear down like you are having a bowel movement” will generally not produce the results that you were expecting… so you can:
    2. Use ice to an infant’s face, or
    3. Have an older child attempt to blow through a partially occluded straw.
  3. Adenosine
    1. Because of it’s extremely short half-life, it should be given as close to the heart as possible.
    2. So will an IO route work?
      1. There is limited data to show that it can be effective.
      2. Humerus likely to be better option than tibia.
      3. It’s worth a try.
    3. What dose?
      1. Typically we are taught to start at 0.1mg/kg then increase to 0.2mg/kg.
      2. Recent review of the literature demonstrated that lower doses of adenosine are less effective than higher doses.
      3. Studies included infants as well as older children.
      4. “A higher initial dose of adenosine (0.2mg/kg to 0.25mg/kg) in both infants and children reduces the risk of unsuccessful cardioversion by 35% (number needed to treat: 3).” (Quail 2012)
  4. What if adenosine didn’t work?
    1. This is relatively uncommon… but…
    2. Order a clean pair of pants for yourself.
    3. Page the Cardiologist.
    4. Then order Procainamide.
      1. For refractory or recurrent pediatric SVT, procainamide has been shown to be more effective than Amiodarone.
      2. Amiodarone may not be as effective as commonly believed.
      1. See nice reviews:
        1. Chang. Circulation. 2010.
        2. Saul. Circulation. 2010.
  • Procainamide 15mg/kg IV over 30-60 minutes
  • And… don’t forget electricity is always an option too!

 

Clark J, Green J. Intraosseous adenosine terminates paroxysmal supraventricular tachycardia in children. BestBETs. http://www.bestbets.org/bets/bet.php?id=2364

Quail MA, Till J. Question 3: Does a higher initial dose of adenosine improve cardioversion rates in supraventricular tachycardia? Arch Dis Child 2012; 97: 177-179.

Chang PM, Silka MJ, Moromisato DY, Bar-Cohen Y. Amiodarone versus procainamide for the acute treatment of recurrent supraventricular tachycardia in pediatric patients. Circulation: Arrhythmia and Electrophysiology. 2010; 3: 134-140.

Saul JP, LaPage MJ. Is it time to tell the emperor he has no clothes? Intravenous amiodarone for supraventricular arrhythmias in children. Circulation: Arrhythmia and Electrophysiology. 2010; 3: 115-117.
 
Doniger SJ, Sharieff GQ. Pediatric dysrhythmias. Pediatr Clin N Am. 2006; 53: 85-105.

 

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