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Beyond Adenosine and SVT

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svt

  1. 1. Supra-ventricular Tachycardias Beyond Adenosine and the Narrow Complex Arjun Rao FRACP ED SCH Randwick NSW
  2. 2. Objectives • Confirm or deepen knowledge of pathophysiology • ECG features and approach to challenges • Anti-arrythmic medications • Toxidrome
  3. 3. Interactive Session • Laptop / Tablet / Phone • “Socrative” – m.socrative.com • “Room number” – 176369 Best lecture ever! - with Arj Rao @ Noosa #lovinlife
  4. 4. Question 1 Where are you from? • • • • • QLD NSW / Vic / Tas SA / NT WA Overseas / Other m.socrative.com 176369
  5. 5. What about this?
  6. 6. 15 yrs What about this? • Tachycardia – rate 150bpm • Rhythm - ?p-waves; very regular • Axis – leftward • QRS - ~7 small squares – 0.28s
  7. 7. Question 2 Is this a narrow or broad complex? • Narrow • Broad • Not sure m.socrative.com 176369
  8. 8. Question 3 How would you characterise this tachycardia? • • • • SVT VT Sinus Tachycardia Not sure m.socrative.com 176369
  9. 9. Abnormal pulse rate or rhythm Dysrhythmia recognition
  10. 10. Abnormal pulse rate or rhythm Key features • Bradycardia • Tachycardia with narrow QRS ⇒ SVT • Tachycardia with wide QRS ⇒ VT
  11. 11. Question 4 Would you give this child adenosine? • Yes • No m.socrative.com 176369
  12. 12. SVT • Common • “Narrow” complex tachycardia • Abnormal “p” • Re-entrant (macro - WPW) • AV Nodal Re-entry • Ectopic Atrial Tachycardia (rare)
  13. 13. SVT • • • • • Most present by 4 months (M:F 3:2) ~ 20% CHD 10-20% WPW ~20% related to fever / drugs Remainder idiopathic
  14. 14. SVT • • • • • Most present by 4 months (M:F 3:2) ~ 20% CHD 10-20% WPW ~20% related to fever / drugs Remainder idiopathic
  15. 15. 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
  16. 16. Orthodromic Re-entry - WPW
  17. 17. Anti-dromic Re-entry AV Node re-entry
  18. 18. SVT Management algorithm Seek expert advice before giving antiarrhythmic drugs
  19. 19. ILCOR 2010 (AHA)
  20. 20. 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
  21. 21. 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]
  22. 22. Question 5: What is a wide QRS Complex • • • • > 40ms > 80ms >100ms >120ms m.socrative.com 176369
  23. 23. Is it really a narrow complex? • 100-120ms ( “3 small squares”) ? • QRS width age related • Broad complex can be related to SVT
  24. 24. Normal QRS width Rijnbeek et al. New Normal Limits for the Paediatric Electrocardiogram, European Heart Journal (2001) 22, 702–711
  25. 25. “Broad complex SVT” • • • • Bundle branch block Ischaemia Antidromic SVT DC Cardioversion if haemodynamically unstable
  26. 26. Broad complex SVT?
  27. 27. Broad Complex SVT • Differentiate from VT? • Adenosine? – Potential for pro-arrhythmia – Probably safe in undifferentiated broad QRS tachycardia
  28. 28. Broad complex SVT v VT
  29. 29. • http://lifeinthefastlane.com/ecglibrary/basics/vt_vs_svt/ • Useful teaching module exploring this in more detail
  30. 30. Other Atrial Tachycardias Keane: Nadas' Pediatric Cardiology, 2nd ed.
  31. 31. 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.
  32. 32. Multifocal Atrial Tachycardia • Rare in children • At least 3 different p-wave morphologies • Treatment difficult
  33. 33. AVNRT • Very rare in young children • Most common mechanism of re-entrant SVT presenting in adulthood • Heamodynamic compromise rare • Treatment generally successful
  34. 34. Junctional Ectopic Tachycardia • • • • • AV node or proximal bundle of HIS Cardiac Surgery AV dissociation Ventricular rate greater than atrial Amiodarone
  35. 35. Other Atrial Tachycardias
  36. 36. Management • • • • • Vagal Manouvers Adenosine Amiodarone Sotolol Other agents – Verapamil – Procainamide/Flecanide
  37. 37. Cardiac Conduction and the Action Potential
  38. 38. Vagal Manouvers ILCOR 2005
  39. 39. 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 m.socrative.com 176369
  40. 40. http://en.wikipedia.org/wiki/Antiarrhythmic_agent
  41. 41. Adenosine
  42. 42. Adenosine • Naturally occurring Nucleoside • Short half-life (~ 10 sec) • Effect on Ca inlfux– AV node block
  43. 43. 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)
  44. 44. Adenosine – Pro-arrhythmic
  45. 45. 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 m.socrative.com 176369
  46. 46. 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
  47. 47. Question 8 What starting dose of adenosine do you use in children? • • • • 50 mcg / kg 100 mcg / kg 200 mcg / kg > 200 mcg / kg m.socrative.com 176369
  48. 48. Adenosine Dose • 50 / 100 / 150 / 200 … • 100 / 200 / 300 [ILCOR/ARC/APLS] • Some retrospective evidence that 200mcg/kg more likely to revert
  49. 49. Amiodarone • Class III anti-arrhythmic agent but multiple effects • Prolongs phase 3 of action potential (potassium channel blocker actions) • Toxicity profile • 5mg/kg
  50. 50. Sotolol • B blocker (Class II) – low doses • and K+ blocker (Class III) – medium high doses • Prolongs PR and QT interval • negative inotrope
  51. 51. 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
  52. 52. Recalcitrant SVT ILCOR
  53. 53. Fleccanide / Procainamide • • • • • Na channel blockers Prolong QRS / QT Proarrythmic Flecainide – oral Procainamide - IV
  54. 54. ECG Toxidromes • Classic ECG Toxidrome is Tricyclic overdose • May present with tachyarrythmia / prolonged intervals (PR, QRS, QT, Heart block)
  55. 55. Tricyclic Overdose
  56. 56. ECG features of Tricyclic Overdose • • • • • Na channel blockade Tall R-wave in AvR Broad QRS “Brugada” pattern Consider NaHC03 if features of Tricyclic overdose
  57. 57. Back to our ECG
  58. 58. Summary • • • • SVT diagnostic and management challenges Cardiac Electrohysiology Medication options and actions ECG Toxidrome

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