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

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?...

Increased/Abnormal Automaticity Sinus tachycardia Ectopic atrial tachycardia Junctional tachycardia

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

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

Assess QRS width

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 110-250 See more broad QRS complexes (>140 msec) than with BBB Concordance in precordial leads-axis same in all leads V1-V6

Second question Narrow complex QRS

Regular narrow QRS tachycardia Sinus tach: ventricular rates 100-180 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)

Sinus tachycardia

Atrial tachycardia May be very hard to differentiate from sinus tachycardia or A-flutter; rates 120-250 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

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

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)

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

Mechanism of AVNRT

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

If ventricular rate is 150 think A-flutter!

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

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

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

Mechanism of orthodromic AVRT-hard to distinguish from AVNRT

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

Junctional tachycardia

Junctional tachycardia with P waves just before QRS complex

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

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

MFAT-multifocal atrial tachycardia Need to see 3 or more different p wave morphologies Irregular; rate usually 100-170 Almost always seen in pulmonary disease patients (COPD) Hard to treat: B-blockers usually contraindicated in pulm. patients and don’t work

MFAT

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

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

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)

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

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

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

arrow points to delta wave-note short PR interval

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

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!

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

Afib with LBBB-see LBBB pattern; note irregularity                                                                                                                                                                                                                                                        

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

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

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

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

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)

The End