1. Supraventricular Tachycardia: Making the diagnosis
Tracy Lawrence, M.D.
Cardiovascular Medicine
USC Medical Center
March 2015

2. Defining Tachycardia Which part? The atrium or the ventricle?
Supraventricular tachycardia: atrial rate or junctional (AV node) rate >100
Ventricular rate can be slow, normal, or fast
So what causes it?...

3. Increased/Abnormal Automaticity
Sinus tachycardia
Ectopic atrial tachycardia
Junctional tachycardia

4. Re-entry
Atrial flutter
Atrial fibrillation
AVNRT
AVRT (WPW)

5. Goals Coming up with differential diagnosis for SVT
Plan for how to systematically review ECGs to evaluate for SVT
Differentitaing Vtac from SVT with wide complex

6. Assess QRS width

7. R/O ventricular tachycardia
Wide QRS complexes
Usually very regular
AV dissociation
P waves march through rhythm or may see retrograde P waves
Usually rates between
See more broad QRS complexes (>140 msec) than with BBB
Concordance in precordial leads-axis same in all leads V1-V6

9. Second question Narrow complex QRS

10. Regular narrow QRS tachycardia
Sinus tach: ventricular rates
May be some slight irregularity due to breathing, normal SA node variation
Normal morphology of P waves (upright in II, III, avF) and normal PR interval
treat underlying condition: B-blockers, Ca channel blockers will not work (ie. Hydrate patient, control pain, treat hypoxemia)

11. Sinus tachycardia

12. Atrial tachycardia
May be very hard to differentiate from sinus tachycardia or A-flutter; rates
Look for P waves that look “funny”
can have 2:1 AV block or can conduct 1:1
Common manifestation of toxicity of digoxin - atrial tachycardia with AV block; see prolonged PR interval often
May see short PR interval if ectopic focus closer to AV node than sinus node would be

13. A-tach with 2:1 block
Notice prolonged PR interval seen with dig toxicity

14. AVNRT Can be very fast, ventricular rates of 150-250 Very regular
P waves may not be seen (buried in QRS)
If present, P waves are retrograde (upside down), just after QRS
Starts in AV node and not in atriatreat with AV nodal blockers (adenosine, B-blocker, Ca channel blocker)

15. AVNRT Re-entry phenomenon
Initiated by premature atrial contraction which allows conduction down a normally unused pathway in the AV node
Stimulates ventricle and then the atrium in retrograde fashion as current travels back up around AV node

16. Mechanism of AVNRT

18. Atrial flutter Atrial rhythm is regular - 300 bpm
Ventricular rate may be regular or irregular due to varying conduction down AV node (3:1 block or 4:1 or 3:2)
Commonly see 2:1 block with ventricular rate 150
Usually see inverted “p” waves or F waves in leads II, III, avF in typical atrial flutter because atrial activation starts inferiorly and heads upward

21. If ventricular rate is 150 think A-flutter!

22. If ventricular rate is ~150, think FLUTTER!
Atrial tach not this fast-rate near 300
Notched T waves imply a hidden P wave

23. AVRT Tricky!! May be hard to tell from AVNRT
Atrial-ventricular re-entry tachycardia
Does not use AV node for tachycardia
Uses accessory, or bypass, tract between atrium and ventricle

24. Types of AVRT
Orthodromic AVRT (More common) – Narrow complex tachycardia in which the wave of depolarization travels down the AV node and retrograde up the accessory pathway. See retrograde p waves.
Antidromic AVRT (Less common) – Wide complex tachycardia in which the wave of depolarization travels down the accessory pathway and retrograde up the AV node.
WPW is an example with its delta wave

25. Mechanism of orthodromic AVRT-hard to distinguish from AVNRT

26. Junctional tachycardia
May see retrograde P waves
Can also see P waves just prior to (almost simultaneous with QRS) due to impulse traveling from AV node to ventricle and also back to atria at same time
QRS is narrow
Rate >100; junction takes over as pacemaker

27. Junctional tachycardia

28. Junctional tachycardia with P waves just before QRS complex

29. SVT with irregular ventricular response
Atrial fibrillation
Atrial flutter
Multifocal atrial tachycardia

30. Atrial fibrillation Undulating atrial baseline
Coarse A-fib may resemble flutter
Look for faster atrial rate (400) and irregularity of these “p” waves
Irregularly irregular

32. MFAT-multifocal atrial tachycardia
Need to see 3 or more different p wave morphologies
Irregular; rate usually
Almost always seen in pulmonary disease patients (COPD)
Hard to treat: B-blockers usually contraindicated in pulm. patients and don’t work

33. MFAT

34. Atrial flutter-again
Don’t forget atrial flutter with variable conduction—will see regularly irregular ventricular rhythm

35. SVT with a wide complex QRS
WPW with antegrade conduction down bypass tract
Bundle branch block with any SVT (SVT with aberrancy)

36. How to differentiate from V-tac?
Look for a typical right or left bundle branch block pattern
Try to find any old ECGs to compare: delta waves seen? Same bundle branch block?
P waves in front of each QRS or AV dissociation
Irregular? If so, less likely Vtac—usually SVT with aberrancy
Afib with BBB
Afib with bypass tract (WPW)

37. Mechanism of antidromic AVRT-longer delay between QRS (wide) and retrograde P wave
Delta wave
Retrograde p wave

38. WPW
If conduct down a bypass tract rapidly see widened QRS as activation is not normal
Signal goes from atrium to bypass tract to ventricle with cell to cell depolarization (slower)
Not subject to normal refractory periods like AV node is so can conduct very fast if atrial signals are fast

39. Beginning of QRS impulse is from accessory pathway-causes widened QRS (delta wave)
Fusion of accessory pathway depolarization and normal conduction occurs to generate a mixed overlapping QRS

40. arrow points to delta wave-note short PR interval

41. What is this? Wide QRS? Is it regular? Approximate ventricular rate?
Is it multifocal Vtac?
Why or why not?

42. How can I tell it’s not Vtac?
Very very fast – ventricular rate is about 300 bpm (Vtac doesn’t go that fast)
Very irregular
Afib with WPW conducting down accessory bypass tract
Defibrillate; do NOT try to slow with B-blocker or Ca channel blocker
If not sure what it is, treat as Vtac!

43. SVT with aberrancy
Any type of SVT with wide QRS due to bundle branch block; often confused with Vtac
Again, look for typical RBBB or LBBB pattern and compare with old ECGs
Look for p waves before each QRS complex
Look for irregularity
If not sure, treat as Vtac; better safe than sorry

44. Afib with LBBB-see LBBB pattern; note irregularity
                                                                                                                                                                                                                                                       

45. Quiz-What is the rhythm?
Hint: What are the arrows trying to show?

46. ANSWER: VENTRICULAR TACHYCARDIA
Are QRS complexes wide?
Is rhythm regular?
Are there P waves associated with QRS complexes in some manner?
Yes
AV dissociation
ANSWER: VENTRICULAR TACHYCARDIA

47. A-tach or A-flutter? Which one is which?V1
avF

48. Atrial tachycardia Atrial flutter Abnormal P wave morphology V1
Regular ventricular response
Abnormally short PR
Atrial rate is 220 V1
Atrial tachycardia
Atrial flutter
avF
Regularly irregular
Atrial rate 300
Typical inverted F waves

49. Summary 1) Wide complex or not 2) Regular ventricular rhythm or not
3) Look for P waves
AV dissociation (V-tac, junctional)
P waves retrograde (AVNRT, AVRT, junctional)
Multiple morphologies or funny looking (MFAT, A-tach, A-flutter)
4) If ventricular rate near 150, look for underlying atrial flutter
5) If extremely fast ventricular rate (>250) with wide bizarre QRS, think WPW
If faced with wide complex tachycardia and not sure if V-tac or SVT with aberrancy, treat as V-tac first (ie. cardiovert, amiodarone)

50. The End