Supraventricular Tachycardia

Raja Selvaraj

Part I - Baseline evaluation (before inducing tachycardia)

Narrow QRS tachycardia

  • Regular
  • Rate >= 100
  • QRSd <= 120
  • AT, AVNRT, orthodromic AVRT

History

  • Age (at onset)
  • Sex
  • Neck pulsations
  • Onset / offset

ECG

  • Long RP / Short RP
  • P wave axis
  • AV ratio
  • ST depression
  • QRS alternans

EP study

  • Baseline measurements
  • Ventricular burst pacing
  • Ventricular extrastimuli
  • Atrial burst pacing
  • Atrial extrastimuli

Ventricular pacing

  • Absent VA conduction
  • Eccentric atrial activation
  • Central atrial activation

Atrial activation

central.png

VA conduction - Nodal conduction

  • Decremental
  • VA dependent on VH
  • Blocks with adenosine
  • VA time reduces with direct His capture

VA and VH

ccentral_vh_prolong.jpg

Parahisian pacing

  • Somewhat difficult to perform
  • Often difficult to interpret
  • Still very useful sometimes

Parahisian pacing - setting up

  • His catheter, slightly pushed in (small A)
  • Start with low output and increase gradually
  • Watch QRS morphology for intermittent His capture

Parahisian pacing - interpretation

  • His capture - narrower QRS, His not seen, RVA early
  • Beware of atrial capture
  • Beware of pure His capture
    • Narrower QRS
    • Isoelectric interval from pacing spike to QRS

Parahisian pacing - interpretation

  • Identify beats with and without His capture
  • Look at atrial activation sequence
  • Measure VA interval

Parahisian pacing - with His capture

  • Nodal conduction - same sequence, shorter VA
  • AP conduction - same sequence, same VA
  • Mixed response - different sequence, shorter VA

Parahisian pacing

parahisian_explanation.jpg

Parahisian

parahisian.jpg

Parahisian

parahisian_latha_2013-12.jpg

Atrial pacing

  • Latent preexcitation
  • Dual AV nodal physiology
    • PR > RR
    • AH jump

PR more than RR

pr_more_rr2.jpg

AH jump - 600/430

pre_RA600430.jpg

AH jump - 600/420

pre_RA600420.jpg

AH jump - 600/410

pre_RA600410.jpg

Atrial extrastimulus - Atrioventricular AP

atrio_vent_pac.jpg

Atrial extrastimulus - Atriofascicular AP

atrio_fasc_pac.png

Atrial extrastimulus - Fasciculoventricular AP

fasciculo_vent_pac.jpg

Other maneuvers

Response to adenosine

adenosine_post_abl_ramesh_2013-12.jpg

Differential pacing

  • VA interval during pacing from apex and base
  • Shorter from apex for nodal conduction
  • Shorter from base for AP conduction

RV apex pacing

rv_apex_va.jpg

RV base pacing

rv_base_va.jpg

Part II - Evaluation of tachycardia

Regular narrow QRS tachycardia

  • AVNRT
  • Orthodromic AVRT
  • Atrial tachycardia

Tachycardia induction

  • Chamber from which induced
  • Induction dependent on critical AH prolongation
  • Induction dependent on antegrade AP conduction block

Regular narrow QRS tachycardia

  • A/V ratio
  • Atrial activation
  • VA time
  • Ventricular overdrive pacing

Narrow QRS tachycardia, 1:1 VA, eccentric atrial activation

preexc_ort.jpg

Narrow QRS tachycardia, 1:1 VA, central atrial activation, very short VA

typical_avnrt.jpg

Narrow QRS tachycardia, 1:1 VA, central atrial activation, VA > 70 ms

svt.jpg

SVT

svt.jpg

Differentiating features

essential_parts.gif

Differentiating features

  • Chamber essential to circuit
  • Focal / reentry
  • Extranodal pathway
  • VA linking
  • Distance from RV apex

Sequential vs simultaneous activation

seq_parallel.jpg

RV overdrive pacing - most useful maneuver

  • Easy to perform and interpret
  • Can distinguish AT from AVNRT / AVRT (VAAV versus VAV)
  • Can distinguish between AVNRT / AVRT (cPPI-TCL, SA-VA)
  • Onset of entrainment can provide clues
  • Can help even if not entrained !

Setting up

  • Burst pacing from right ventricle - apex / base
  • Sync on
  • Tachycardia CL - 30 ms
  • Pace until atrium entrained
  • Stop pacing

What to look for ?

  • Don't 'eyeball'
  • Does tachycardia continue ?
  • Was the atrium entrained ?
  • Which is the last entrained A ?
  • Sequence - VAV or VAAV

What to look for ?

  • corrected PPI - TCL
  • SA - VA
  • Is there fusion during entrainment ?
  • Beginning of entrainment - A or His ?
  • How many beats to entrain ?

RV pacing in narrow QRS tachycardia - Rule out (or in) AT

vav.jpg

RV pacing in narrow QRS tachycardia - Rule out (or in) AT

vav_measurements_atrium_entrain.jpg

RV pacing in narrow QRS tachycardia.

pseudoVAAV.png

Why all this fuss about measurement ?

pseudo_vaav_measurements.jpg

RV pacing in AT - VAAV

VAAV.jpg

RV pacing in narrow QRS tachycardia - AVNRT / AVRT

vav_measurements_ppi.jpg

SA / VA intervals

sa_va.jpg

Fusion during entrainment ?

fusion.jpg

Entrainment

VOP_entrainment.jpg

Beginning of entrainment can give a clue

entrainment_onset.jpg

  • Atrial acceleration in transition zone
  • A entrainment before H entrainment

Could not entrain - useful information ?

av_dissociation.jpg

Summary

  • VAAV identifies AT, VAV rules out
  • SA - VA and PPI - TCL are longer for AVNRT
  • Can use basal pacing if responses are equivocal
  • A entrained earlier for AVRT, entrained before His

His refractory PVC

  • Little more difficult to perform and interpret
  • Very useful maneuver
  • Especially differentiate septal AP from AVNRT

His refractory PVC - setting up

  • R synchronised single extrastimuli
  • Check that sync is working
  • Start 30 ms less than RR
  • Decrement by 10 ms
  • Continue until refractoriness or tachycardia termination

His refractory PVC - measurement and interpretation

  • Confirm cycle length is stable
  • Measure AA around each PVC to find longest CI at which PVC preexcites A
  • Decide if His is refractory at this time

His refractory PVCs - responses

  • Advance atrial activation without change in sequence
  • Delay atrial activation without change in sequence
  • Terminate tachycardia without conduction to atrium
  • Does not alter atrial activation

PVC during tachycardia

his_pvc.jpg

PVC terminates tachycardia

his_ref_pvc.jpg

Other clues during narrow QRS tachycardia

  • VA unlinking - spontaneous or after atrial burst
  • Cycle length and VA changes with bundle branch block
  • Spontaneous termination

Spontaneous termination

spont_term.jpg

Bundle branch block

lbbb_narrow.jpg

Bundle branch block

lbbb_narrow_measurements.jpg

Bundle branch block

coumel.jpg

Parahisian

parahisian.jpg

Parahisian

parahisian_latha_2013-12.jpg

Pre-ablation

parahisian_pre.jpg

Post ablation

parahisian_post.jpg

Summary

  • Understanding of basic electrophysiology of arrhythmias
  • Practice is important
  • Although not required at most time, will prove critical in select cases