Supraventricular Tachycardia in Infancy and Childhood

1. Supraventricular Tachycardiain Infancy and Childhood Terrence Chun, MD Pediatric Electrophysiology and Pacing

2. Cardiac electrical anatomy

3. SVT - Overview • Rapid rhythm that involves or is driven by structures in the upper heart • Incidence up to 1:250 children • Generally well-tolerated, even fast rates • Risk of life-threatening arrhythmias is uncommon

4. Narrow vs. Wide QRS • Not all narrow QRS complex tachycardia is supraventricular tachycardia • Not all wide QRS complex tachycardia is ventricular tachycardia

5. SVT Mechanisms - Overview • Reentrant rhythms • Automatic rhythms

6. SVT mechanisms –Automatic Rhythms • Originate from a particular focus • “Warm-up” and “cool-down” behavior • Respond to drugs and maneuvers that affect myocardial automaticity • May be suppressed by faster rates • Usually do not respond to cardioversion (typically pause, then restart)

7. SVT mechanisms –Automatic Rhythms • Left atrial focus • 2:1 AVN conduction

8. SVT mechanisms –Reentrant rhythms • Requires a “circuit” of tissue to create repetitive activation • Must have appropriate conditions to perpetuate reentrant rhythm • Usually abrupt onset and termination • Regular, with little variation in rate • Often will respond to cardioversion

9. SVT mechanisms –Reentrant rhythms

10. Diagnostic methods • 12-lead electrocardiogram ! ! ! • Post-op atrial/ventricular pacing wires • Esophageal pacing leads • Adenosine can be diagnostic • Invasive electrophysiology study

11. Diagnostic methods • Always • Always • Always record a rhythm strip during any intervention (adenosine, cardioversion, Valsalva, etc.)

12. Diagnostic methods • Record a rhythm strip

13. ECG clues to diagnosis • Wide vs. narrow complex • Regular vs. irregular • Abrupt vs. gradual • P wave relationship to QRS

14. Parade of Rhythms Automatic Arrhythmias

15. Automatic rhythms –Sinus Tachycardia • Sinus node – fish-shaped structure with “head” at SVC-RA junction and “tail” extending along RA wall • S-tach usually due to increased sympathetic discharge, fever, anemia, hypovolemia, hyperthyroidism, etc. • Inappropriate sinus tachycardia - rare

16. Automatic rhythms – Sinus Tachycardia • Dx • Rate greater than normal range, but usually less than 200 • P wave axis normal (0 ~ +90°) • PR interval normal • Tx • Treat the cause

17. Automatic rhythms – Automatic Atrial Tachycardia • Originates from a focus in either the right or left atrium, or atrial septum • Commonly from atrial appendages, crista terminalis, pulmonary veins • Can also be due to central lines, etc. • Also called “ectopic atrial tachycardia” • although any automatic rhythm other than sinus rhythm is technically “ectopic”

18. Automatic rhythms – Automatic Atrial Tachycardia • Dx • Speeds-up and slows-down, rates vary • P wave axis abnormal • PR interval may be abnormal (it is a function of distance from focus to AVN) • May see 2° AV block (e.g. Wenckebach or 2:1 at higher atrial rates) • Adenosine  P waves “march through” despite AV block

19. Automatic rhythms – Automatic Atrial Tachycardia

20. Automatic rhythms – Automatic Atrial Tachycardia • Tx • Remove source (check CXR and pull back PICC) • Beta-blockers • Esmolol infusion in ICU setting • propranolol, atenolol • Amiodarone, others • Catheter ablation

21. Automatic rhythms – Junctional Tachycardia • Originates from around the AV junction • Also called “JET” (Junctional Ectopic Tachycardia), because it sounds cool • Rate 170-200+ • Most commonly seen post-operatively, usually self-limited • Congenital forms, more persistent

22. Automatic rhythms – Junctional Tachycardia • Dx • AV dissynchrony • Sinus P wave at different rate than narrow QRS • Atrial wire ECG (in post-op with pacing wires) • “Cannon a-waves” on CVP monitor • Retrograde P waves (abnormal Pw axis) • May be on top, before, or after QRS

23. Automatic rhythms – Junctional Tachycardia • Cannon a-waves

24. Automatic rhythms – Junctional Tachycardia • Tx • Reduce catecholamines • Decrease inotropic drips • Pain control and sedation • Cooling/hypothermia • Drugs (amiodarone) • ECMO • Catheter ablation(?)

25. Parade of Rhythms Reentrant Arrhythmias

26. Reentrant rhythms – Pathway Mediated Tachycardia • Bypass tract of conductive tissue connects atrium to ventricle • Most common mechanism of SVT in children • Rate 180-240 • May be “manifest” (e.g. WPW) or concealed (no preexcitation) • Pathway can be anywhere on mitral or tricuspid annuli, usually left-sided

27. Reentrant rhythms – Pathway Mediated Tachycardia • Orthodromic reciprocating tachycardia • “Runs correctly” with normal conduction • Down AV node (narrow QRS) • Up accessory pathway (retrograde) • Retrograde P waves may be visible after QRS • Antidromic reciprocating tachycardia • “Runs against” normal conduction • Down accessory pathway (wide QRS) • Up AV node (retrograde) • Less common

28. Reentrant rhythms – Pathway Mediated Tachycardia • Dx • Electrocardiogram • Rhythm strips of start and stop of SVT

29. Reentrant rhythms – Pathway Mediated Tachycardia • Tx • Valsalva maneuvers, Ice to face • Adenosine (technique matters!) • Antiarrhythmic drugs • Beta blockers (watch blood glucose in infants!) • Digoxin (limited value; digitalization only in difficult situations) • Others (Verapamil, Flecainide, Sotolol, etc.) • Catheter ablation

30. Reentrant rhythms – Wolff-Parkinson-White Syndrome • Electrocardiogram findings • Short PR interval • Wide QRS complex • Delta wave

31. Reentrant rhythms – Wolff-Parkinson-White Syndrome

32. Reentrant rhythms – Wolff-Parkinson-White Syndrome • Clinical symptoms • Palpitations • SVT • Note narrow QRS and lack of delta wave!

33. Reentrant rhythms – Wolff-Parkinson-White Syndrome • Sudden death(!) • Atrial fibrillation • Rapid conduction over bypass tract • Ventricular fibrillation • Risk 0.1-0.6% per year

34. Reentrant rhythms – Wolff-Parkinson-White Syndrome • Tx • Tachycardia control • Recognition • ±Drugs (patient/family choice) • Digoxin generally contraindicated • Risk stratification • Holter • Exercise testing • Invasive electrophysiology testing • Catheter ablation

35. Reentrant rhythms – AV Node Reentry Tachycardia • More common in teens and adults • Tachycardia circuit contained within atrioventricular node • Activates atria at the “top” of the circuit, ventricles at “bottom” of circuit, nearly simultaneously • Rate 200-250 • Usually cannot see retrograde P waves

36. Reentrant rhythms – AV Node Reentry Tachycardia

37. Reentrant rhythms – AV Node Reentry Tachycardia • Tx • Adenosine • Cardioversion • ±Pharmacotherapy • Beta blockers • Digoxin • Others • Catheter ablation

38. Reentrant rhythms – Atrial Flutter • “Flutter” circuit around anatomic structures in atrium • Eustachian valve • Crista terminalis • Fossa ovalis • Surgical incisions

39. Reentrant rhythms – Atrial Flutter • Atrial rate ~300 (higher in neonates) • Ventricular rate depends on AV node conduction • 1:1  300/min • 2:1  150/min • 3:1  100/min • May be 3:1 then 2:1 then…

40. Reentrant rhythms – Atrial Flutter • Sawtooth “flutter” waves (may or may not be helpful)

41. Reentrant rhythms – Atrial Flutter • Dx • Electrocardiogram • Adenosine blocks AV node; flutter waves continue • Tx • Rate control – digoxin, beta blockers, etc. • Overdrive pacing • DC cardioversion • Catheter ablation

42. Threatening Rhythms • Atrial fibrillation in high-risk WPW • Danger of ventricular fibrillation • Persistent prolonged SVT • Tachycardia induced cardiomyopathy (reversible) • SVT in compromised cardiac status • Syncope or cardiovascular collapse

43. Treatment Pearls

44. Adenosine • 0.1-0.4 mg/kg/dose • Very short half-life (seconds) • Central administration can be helpful, but not necessary • Rapid saline bolus (5-10 ml) essential • Stopcock on venous access is helpful

45. DC Cardioversion • Dose • Cardioversion 0.25-1 J/kg • Defibrillation 1-2 J/kg • Synchronized (avoids making worse) • Paddles – front+apex • Patches • Front+apex • Front+back

46. Catheter Ablation • Multiple catheters • Size limitations • Ideally > 15 kg, but can be done in infants if necessary • Can be curative • ~95% success rate in children

47. Record a Rhythm Strip! • Especially during interventions • Most SVT in infants and children is hemodynamically well-tolerated • Proper diagnosis can guide appropriate therapy • RA/LA/RL/LL limb leads give 6 electrograms (I, II, III, aVL, aVR, aVF)