18. SVT
•
•
•
•
•
Most present by 4 months (M:F 3:2)
~ 20% CHD
10-20% WPW
~20% related to fever / drugs
Remainder idiopathic
19. SVT
•
•
•
•
•
Most present by 4 months (M:F 3:2)
~ 20% CHD
10-20% WPW
~20% related to fever / drugs
Remainder idiopathic
20. SVT: Re-entry
• Re-entrant current needs to
find excitable cells
• Cells are not excitable during
their refractory period
• Therapy for SVT involves
decreasing conduction velocity
or increasing refractory period
http://www.cvphysiology.com
25. Challenges of “Narrow Complex Tachycardia”
•
•
•
•
•
•
SVT v Sinus Tachycardia
Is it really a narrow complex?
Broad complex SVT
Other atrial tachycardias
Management beyond adenosine
Recalcitrant SVT
26. SVT v Sinus Tachycardia
•
•
•
•
Rate
Regularity
Therapeutic trial of adenosine ?
P-waves
– “In both rhythms a P wave may be discernible”
[ARC 12.5 2010]
27. Question 5:
What is a wide QRS Complex
•
•
•
•
> 40ms
> 80ms
>100ms
>120ms
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28. Is it really a narrow complex?
• 100-120ms ( “3 small squares”) ?
• QRS width age related
• Broad complex can be related to SVT
29. Normal QRS width
Rijnbeek et al. New Normal Limits for the Paediatric Electrocardiogram, European Heart Journal
(2001) 22, 702–711
37. Ectopic Atrial Tachycardia
•
•
•
•
•
•
< 10% SVT
Can be difficult to treat
Consider in child with cardiomyopathy
Beat to beat variability
P-wave axis
Adenosine may be ineffective, DC
cardioversion ineffective
• Digoxin, Amiodarone
Keane: Nadas' Pediatric Cardiology, 2nd ed.
39. AVNRT
• Very rare in young children
• Most common mechanism of re-entrant
SVT presenting in adulthood
• Heamodynamic compromise rare
• Treatment generally successful
45. Question 6 – Which therapies
have you used to manage acute
SVT?
1.
2.
3.
4.
Vagal / Adenosine
[1] + Amiodarone
[1 or 2] + Sotolol
[1 or 2 or 3] + Procainamide/Fleccainide
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51. Adenosine
• Give centrally (cubital) – three way tap
• Chest tightness, metallic taste in mouth
• Useful for re-entry SVT and some atrial
tachycardia (AV Node)
• AF -> VF through accessory pathway
described
• Pharmacological effects may be blunted in
those taking methylxanthines (ie caffeine)
53. Question 7
A 4yr old child with a history of asthma BIBA
on continuous nebulised salbutamol –
monitor shows SVT. Vagal manouvers are
unsuccessful. Would you use adenosine?
• No
• Yes
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54. Adenosine and Asthma
• Adenosine receptors
• Can worsen broncho-constriction in children
with asthma
• But – short lived
• Alternative agent?
• Case reports of successful Rx of SVT
precipitated by salbutamol
55. Question 8
What starting dose of adenosine
do you use in children?
•
•
•
•
50 mcg / kg
100 mcg / kg
200 mcg / kg
> 200 mcg / kg
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56. Adenosine Dose
• 50 / 100 / 150 / 200 …
• 100 / 200 / 300 [ILCOR/ARC/APLS]
• Some retrospective evidence that
200mcg/kg more likely to revert
57. Amiodarone
• Class III anti-arrhythmic agent but multiple
effects
• Prolongs phase 3 of action potential
(potassium channel blocker actions)
• Toxicity profile
• 5mg/kg
58. Sotolol
• B blocker (Class II) – low doses
• and K+ blocker (Class III) – medium high
doses
• Prolongs PR and QT interval
• negative inotrope
59. Verapamil
• Calcium channel blocker – Class IV
• Major action is on Sa and AV node (Ca
channel dependent depolarisation)
• Decreased AV node conduction and increased
refractory time
• Negative inotrope
64. ECG features of Tricyclic Overdose
•
•
•
•
•
Na channel blockade
Tall R-wave in AvR
Broad QRS
“Brugada” pattern
Consider NaHC03 if features of Tricyclic
overdose