preexcitation syndromes

Accessory Pathways

General Concepts / Preexcitation Variants

Horacio Jose QuirogaEP Fellow

Arrhythmia Service

EP Rounds – Arrhythmia Service

Accessory PathwaysObjectives

• Analyze common and uncommon types of preexcitation

• Discuss diagnosis and differential diagnosis

• Review decision making with asymptomatic patients

Accessory PathwaysGeneral Concepts / Preexcitation Variants

• Wolff Parkinson White syndrome

• Lown Ganong Levine syndrome

• Accessory Pathways with anterograde decremental conduction

• Updated review of decision making with asymptomatic patients

Accessory PathwaysWolff Parkinson White Syndrome


• Short PR interval• Wide QRS• Short or negative HV interval• Reentrant tachycardias• Accessory AV conduction of atrial

arrhythmias

Fused Ventricular Activation


Orthodromic Tachycardia


Antidromic Tachycardia


Localization of the Accessory Pathway

Ecg Localization AlgorithmsDelta Wave Morphology

New algorithm for the localization of APs using a baseline Ecg. Fitzpatrick et al. JACC 1994; 23: 107 - 16



QRS Transition

After V2 At or before V1



QRS Transition

After V2 At or before V1Between V1 and V2

R/S Lead 1



QRS Transition




EP

• Differential Atrial Pacing

• Retrograde atrial activation sequence

• VA time during Bundle Branch Block development

• Preexcitation Index

Morillo CA et al, The Wolff Parkinson White Syndrome



“Applied to either AV or VA time, fused conduction or

reentrant tachycardias, the closer we get to the pathway

the shorter will be the conduction”


Differential Atrial Pacing

MaximumPreexcitation



MinimumPreexcitation


Retrograde Atrial Activation


Functional Bundle Branch Block



Key Points

• Functional Block must happen ipsilateral to the Accessory Pathway

• When to measure the change in the VA interval

• Where to measure the change in the VA interval

• Differentiate between left lateral and septal Accessory Pathways


Preexcitation Index

The preexcitacion index: An aid in determining the mechanism of SVT and localizing accessory pathways. Circulation 1986, 74: 493 - 500


Preexcitation Index


“The closer to the excitable gap of the circuit the PVC is delivered, the longer is the V1 – V2

that preexcites the tachycardia”


Preexcitation Index

Tachycardia Cycle Length

Longest V1 – V2 for sensed PVCs thatpreexcite the Tachycardia

Minus



Preexcitation Index

Tachycardia Cycle Length

Longest V1 – V2 for sensed PVCs thatpreexcite the Tachycardia

Minus


QRS QRS

His Refractoriness

S1

Anteroseptal / Right sided AP

Px Ix < 45


Preexcitation Index


QRS QRS

His Refractoriness

S1

Anteroseptal / Right sided AP

Px Ix < 45

S1

Left free Wall APs

Px Ix > 75

AVNRT

Px Ix > 100

S1


Preexcitation Index


Functional Left Bundle Branch Block


Tachycardia induction



Induction by APD



The closer to the AP we pace, the easier the orthodromic SVT is induced



APD with 1:2 response



Delay in the HPS allows induction after a PVC


Maneuvers during Orthodromic Tachycardia

AVN AVNSP FP

A A The V – A – V Response

A technique for the rapid diagnosis of AT in the EP Laboratory. J Am Coll Cardiol 1999, 33: 775 - 781



A A A A

The V – A – A – V Response


AVN AVN AVNAVN AVN

V V V V Ventricular Burst Pacing



A A A

What if there is an Atrial Tachycardia and a concealed accesory pathway?


AVN AVN AVN

V V V Ventricular Burst Pacing

AVN

Concept also applicableto dual AV Node Physiology





The post pacing interval and VA time

Reentrantcircuit

The stimulus train for entrainment must be faster than the tachycardia cycle length but the slowest capable of entraining it





AVNRT

AV

RT

Activation in parallel Activation in series

A

VVA

VA time



Ventricular Entrainment Tachycardia


Maneuvers during Antidromic Tachycardia

Accessory PathwaysLown Ganong Levine Syndrome

• Short PR Interval

• Narrow QRS

• Supraventricular Tachycardias

Atriohisian AP

Enhanced AV Conduction


Atriohisian AP


• Short HV interval due to retrograde His activation (His and V activated in paralel instead of in series)

• Dual AVN Phisiology like behaviour due to block in the Atrio His connection


Atriohisian APEnhanced AV Conduction

• AH < 60 msec

• 1:1 AV conduction with atrial pacing at 300 msec

• AH increase < 100 msec between

SR and atrial pacing at 300 msec



• AH < 60 msec

• 1:1 AV conduction with atrial pacing at 300 msec

• AH increase < 100 msec between

SR and atrial pacing at 300 msec

Reentrant SVTsFast conducted AF

Fixed AH duringatrial burst pacing

Short HV interval

Atriohisian AP

Accessory PathwaysResponse of Atriohisian AP to APDs

Accessory PathwaysEnhanced AV Conduction

Accessory PathwaysAnterograde Decremental Conduction

Atriofascicular and Atrioventricular APs

Nodofascicular and Nodoventricular APs

Fasciculoventricular APs


Atriofascicular AP

Atrioventricular AP

Nodofascicular AP

Nodoventricular AP

Fasciculoventricular AP

Extremely uncommon

No Tachycardias involved


When should we think about Atriofascicular or Atrioventricular Aps?

• Young patients with frequent palpitations

• Normal baseline Ecg (No Preexcitation)

• Wide complex Tachycardia with LBBB morphology / left axis deviation /

late R wave transition

When should we think about Nodofascicular or Nodoventricular APs?

• The same as above

• VA dissociation during Tachycardia

Accessory PathwaysAtriofascicular Accessory Pathways

• No preexcitation during sinus rhythm

• Preexcitation: Narrow QRS with true LBBB pattern (not typical preexcitation) with narrow QRS and late precordial R transition

• Decremental (Rate dependent) anterograde AP conduction with preferential conduction from right rather than left atrial pacing.

• Right ventricular apical electrogram

• No retrograde AP conduction (only retrograde AVN conduction)

Key Points


• No preexcitation during sinus rhythm

• Preexcitation: True LBBB pattern (not typical preexcitation)

• Decremental (Rate dependent) antegrade AP conduction with preferential conduction from right rather than left atrial pacing

• Right ventricular apical electrogram

• No retrograde AP conduction (only retrograde AVN conduction)

HBp

III

V1

RV

RAA

HBd

H*

H

RB

A

65

A

ALateral

TA

100 ms

Key Points


Incremental Atrial Burst Pacing

Decremental Pathways Increasing Preexcitation with prolongation of the P – Delta interval

Regular AV Pathways Increasing Preexcitation with constant P – Delta interval


Response to Adenosine


Atriofascicular / Atrioventricular: The closer to the AP we pace, the more preexcited it gets (Differential Atrial Pacing)

Nodofascicular / Nodoventricular: Preexcitation is similar with differentSites of atrial pacing (impulse needs to go through the AVN to reach the AP)

Key Points


Atriofascicular vs Atrioventricular APs

Key Points

Atriofascicular: True LBBB Morphology with narrow QRS (150 msec or less) and late R wave transition (V4 – V5)

Atrioventricular: LBBB like morphology with broader QRSand broad initial R in V1

AV NodeRA

LV

LA

His Bundle

RBB LBB

RV

“Duplication of Normal Conduction System”

Accessory AV Node

Accessory His Bundle

Accessory Right Bundle Branch


101 ms

18 ms

Range of H* LocationAround the

Tricuspid Annulus

LAO Projection

HB

H*


HBp

CSp

RV

390

HBd

CSd

S

Retro RB

H

RB

290VS

H

IIIV1

RAAA AA A


270300380

HBp

IIIV1

RAA

CSp

RV

HBd

CSd

VS340

S

A

V300

V280Retro RB

A

SS


390360

HBp

IIIV1

CSp

RV

HBd

CSd

RAA

VS

250S

A

Retro RB

A

V360

S

AA

S S S

Block390


Fixed VH time at 40 ms suggests block in the AVN and retrograde His activation through an atrioventricular AP

Accessory PathwaysAntidromic Tachycardia Induction

PAC

Accessory PathwaysAntidromic Tachycardia Induction

PACPVC



Key Points

Antidromic Tachycardia

VH Time VH 35 – 50 AtriofascicularVH 50 – 80 Atrioventricular



Key Points

VH Time VH 35 – 50 AtriofascicularVH 50 – 80 Atrioventricular

VH < 10 or negative andHA < 50 msec favors AVNRT

with innocent bystander

AVNRT is confirmed if the HA interval is longer than the HA after the PVC that induces the tachycardia

( HA Criteria)

Accessory PathwaysManeuvers during Antidromic Tachycardia

Confirms AVRT

Rules out preexcited AVNRT

Rules out nodofascicular AP

Accessory PathwaysManeuvers during Antidromic Tachycardia

Ventricular Entrainment of the Tachycardia: Fixed VH interval during entrainment and post pacing first beat of SVT confirms AVRT over AVNRT with bystander AP


Summary of Concepts

• Atriofascicular and Atrioventricular are by far the most common types. They show decremental properties and conduct only on an anterograde fashion

• Patients usually present with recurrent wide complex SVTs due to antidromic tachycardias or AVNRT with bystander pathways.

• Atriofascicular and Atrioventricular respond to differential atrial pacing, while nodofascicular and nodoventricular do not.

• The QRS morphology and VH time during tachycardia can successfully differentiate between connections to the fascicles and to the ventricles.

• Nodofascicular and Nodoventricular APs should be considered with wide complex SVTs with LBBB morphology and VA dissociation. VH dissociation rule them out and rule in VT arising from the right ventricle.

• His bundle pacing with preexcitation and no inducible tachycardia confirms Fasciculoventricular APs.


• Which patients could be considered for conservative management?

Decision making with asymptomatic patients

•How can we identify high risk patients?


• Which patients could be considered for conservative management?

Decision making with asymptomatic patients

•How can we identify high risk patients?

Asymptomatic patients with low risk who don’t want an invasive approach

Patients with low risk APs close to normal conduction system


• Patients with SPERRI less than 220 ms

• Multiple accessory pathways / Previous syncopal episodes

• Patients with intermitent preexcitation

• Patients with loss of preexcitation during exercise test

Risk identification


• An exercise test is a reasonable component of evaluation if the Ecg exhibits persistent preexcitation (IIA B)

• Invasive risk stratisfication to assess the SPERRI is reasonable in patients whose noninvasive testing does not demonstrate clear and abrupt loss of preexcitation (IIA B)

• Patients with SPERRI < 250 ms in AF are at increased risk for SCD. It is reasonable to proceed with RF considering anatomical location (IIA B)

• Patients with SPERRI > 250 ms are at low risk for SCD and it is reasonable to defer RF if the patient or location of the AP imply higher risk (IIA C)

• Asymptomatic patients with structural heart disease and / or ventricular dysfunction secondary to dyssynchronous contractions may be considered for RF regardless of anterograde characteristics of the bypass tract (IIB C)

PACES / HRS Expert Consensus on the Management of the asymptomatic young patient with a WPW electrocardiographic pattern. Hearth Rhythm 2012; 9: 1006 - 1024

preexcitation syndromes

Documents

localization of aps

accessory pathwayapplied

baseline ecg

qrs transitionafter

fused conduction

v2rs lead

v1between v1