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- 1. Supra-ventricular Tachycardias Beyond Adenosine and the Narrow Complex Arjun Rao FRACP ED SCH Randwick NSW
- 3. Objectives • Confirm or deepen knowledge of pathophysiology • ECG features and approach to challenges • Anti-arrythmic medications • Toxidrome
- 4. Interactive Session • Laptop / Tablet / Phone • “Socrative” – m.socrative.com • “Room number” – 176369 Best lecture ever! - with Arj Rao @ Noosa #lovinlife
- 5. Question 1 Where are you from? • • • • • QLD NSW / Vic / Tas SA / NT WA Overseas / Other m.socrative.com 176369
- 10. What about this?
- 11. 15 yrs What about this? • Tachycardia – rate 150bpm • Rhythm - ?p-waves; very regular • Axis – leftward • QRS - ~7 small squares – 0.28s
- 12. Question 2 Is this a narrow or broad complex? • Narrow • Broad • Not sure m.socrative.com 176369
- 13. Question 3 How would you characterise this tachycardia? • • • • SVT VT Sinus Tachycardia Not sure m.socrative.com 176369
- 14. Abnormal pulse rate or rhythm Dysrhythmia recognition
- 15. Abnormal pulse rate or rhythm Key features • Bradycardia • Tachycardia with narrow QRS ⇒ SVT • Tachycardia with wide QRS ⇒ VT
- 16. Question 4 Would you give this child adenosine? • Yes • No m.socrative.com 176369
- 17. SVT • Common • “Narrow” complex tachycardia • Abnormal “p” • Re-entrant (macro - WPW) • AV Nodal Re-entry • Ectopic Atrial Tachycardia (rare)
- 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
- 21. Orthodromic Re-entry - WPW
- 22. Anti-dromic Re-entry AV Node re-entry
- 23. SVT Management algorithm Seek expert advice before giving antiarrhythmic drugs
- 24. ILCOR 2010 (AHA)
- 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 m.socrative.com 176369
- 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
- 31. “Broad complex SVT” • • • • Bundle branch block Ischaemia Antidromic SVT DC Cardioversion if haemodynamically unstable
- 33. Broad Complex SVT • Differentiate from VT? • Adenosine? – Potential for pro-arrhythmia – Probably safe in undifferentiated broad QRS tachycardia
- 34. Broad complex SVT v VT
- 35. • http://lifeinthefastlane.com/ecglibrary/basics/vt_vs_svt/ • Useful teaching module exploring this in more detail
- 36. Other Atrial Tachycardias Keane: Nadas' Pediatric Cardiology, 2nd ed.
- 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.
- 38. Multifocal Atrial Tachycardia • Rare in children • At least 3 different p-wave morphologies • Treatment difficult
- 39. AVNRT • Very rare in young children • Most common mechanism of re-entrant SVT presenting in adulthood • Heamodynamic compromise rare • Treatment generally successful
- 40. Junctional Ectopic Tachycardia • • • • • AV node or proximal bundle of HIS Cardiac Surgery AV dissociation Ventricular rate greater than atrial Amiodarone
- 42. Management • • • • • Vagal Manouvers Adenosine Amiodarone Sotolol Other agents – Verapamil – Procainamide/Flecanide
- 43. Cardiac Conduction and the Action Potential
- 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 m.socrative.com 176369
- 48. Adenosine
- 50. Adenosine • Naturally occurring Nucleoside • Short half-life (~ 10 sec) • Effect on Ca inlfux– AV node block
- 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 m.socrative.com 176369
- 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 m.socrative.com 176369
- 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
- 61. Fleccanide / Procainamide • • • • • Na channel blockers Prolong QRS / QT Proarrythmic Flecainide – oral Procainamide - IV
- 62. ECG Toxidromes • Classic ECG Toxidrome is Tricyclic overdose • May present with tachyarrythmia / prolonged intervals (PR, QRS, QT, Heart block)
- 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
- 65. Back to our ECG
- 66. Summary • • • • SVT diagnostic and management challenges Cardiac Electrohysiology Medication options and actions ECG Toxidrome