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Beyond Adenosine and SVT

Beyond Adenosine and SVT

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svt svt Presentation Transcript

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