Adv EP Lesson 4 - AVNRT/AVRT/Atrial Flutter/Atrial Tachy/Atrial Fibrillation

AVNRT

localized in the AV node

slow antegrade pathway (alpha) with fast retrograde pathway

block in fast pathway because it is refractory

AVNRT EKG and Intracardiac ECG characterisitc

p wave not visible because they happen at the same time

short RP tachycardia, narrow QRS

Retrograde P wave after QRS or hidden within QRS

CS intracardiac electrograms appear to be “stacked”

short VA interval time

typical AVNRT

down slow pathway antegrade and up fast retrograde

slow fast AVNRT

atypical AVNRT

down fast pathway anterograde and up the slow retrograde

fast-slow AVNRT

AVNRT pacing maneuver

atrial extra stimulus; drive train of 6-8 beats at a given rate S1 followed by a premature beat (S2) and then a pause in pacing. The next drive train (S1) will be at the same pacing rate but the premature beat (S2) will be introduced 10 ms earlier than the previous S2.  This series of pacing maneuvers will continue until either the atria becomes refractory or dual AV nodal physiology is identified.

dual AV nodal physiology indicator

a jump or sudden change in AH interval by greater than 50ms with only a 10ms decrease in prematurity of the S2

As and Vs on top of each other indicating AVNRT

Entrainment in AVNRT

used to rule out presence of a bypass tract

PPI - TCL > 115ms then it’s AVNRT in RV cath

SA-VA > 85ms in V1 cath

slow fast AVNRT

slow slow AVNRT

fast slow AVNRT

left variant AVNRT

triangle of koch

septal leaflet of the tricuspid valve, CS ostium and the tendon of Todaro

location of AVNRT

triangle of koch

advantage to focal cryo

allows for ablation during tachy

what to be careful of during cryo

AV block because it can occur during it with the vicinity of the cath to the AV node

which one is cryo which one is RF

A=RF

B=Cryo

RF ablation success indicators

junctional beats means ablating in the correct location

cryoablation success indicators

noninducibility or antergrade termination over the slow path

freeze thaw freeze

increaes ice formation of cryo lesion

AVNRT procedural end points

• The use of Isoproterenol during post procedure testing phase may uncover dormant conduction.

  • 
    

    Complete slow pathway elimination (non-inducibility of echo beats and A-H jump) may contribute to higher rates of long term efficacy.

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  Procedural end-points are usually assessed 30 min post ablation and vary by physician. Typically, end points include elimination of the slow pathway, or non-inducibility of tachycardia with max. 1 echo beat, with or without Isoproteranol administration.

During cryoablation, an  AV ratio of 1:4-1:10 is acceptable T/F

F because targeted a small atrial and large ventricular signal, often between 1:4 to 1:2

WPW ECG indicator

short pr inteval <120ms

long QRS complex >110ms

delta wave

AVRT

bundle of kent is present and acts as an accessory pathway where a reentry circuit can occur

AVRT with antidromic conduction

initiated by premature contractions

label these as AVRT WPW, orthodromic, or antidromic

a WPW

b orthodromix reentrant tachy

c antidromic reentrant tachy

Orthodromic accessory pathway manifests on an ECG as a delta wave T/F

F

location of accessory pathways

right lateral, aneroseptal or mid septal, posteroseptal, or left lateral

manifest pathway

• Manifests on ECG as a delta wave at baseline (pre-excitation, WPW)

  • May conduct both retrograde and antegrade

concealed pathway

• Normal ECG at baseline (no delta wave)

  • Retrograde conduction only

AVRT extra stimlus pacing maneuver

ventricular extra stimulus drive train of 6 to 8 beats paced at a given rate (S1) followed by a premature beat (S2) and then a pause in pacing. The next drive train (S1) will be at the same pacing rate but the premature beat (S2) will be introduced 10 ms earlier than the previous S2.  In the example below, retrograde atrial signal travels from the proximal to distal CS electrodes (right to left), displaying concentric activation pattern. There is also a V-A prolongation suggesting that the signal traversed the AV node. This would rule out the presence of an AP.

AVRT pacing maneuvers

atrial decremental pacing and ventricular extra stimilus

how to know if it is left sided accessory path/eccentric

During ventricular extra-stimulus pacing, if the retrograde atrial signal travels from the distal to proximal CS electrodes (left to right),

AVRT decremental pacing maneuver

premature atrial pacing leads to an A-H jump (conduction is occuring over slow pathway) and tachycardia is induced

In a patient with an accessory pathway, VA interval will _______ on decremental ventricular pacing.

remain unchanged

what will reveal the location of the AP

when mapping an AP, the part of the chamber that is activated first

ablation endpoint for AVRT

    Delta wave disappears, return to normal ECG

    Tachycardia is terminated & non-inducible

    Wait period (usually 30 min)

    Adenosine given to see if return of pathway occurs 

atrial flutter

atria contract at high rates like 300bpm

sinus node signal propagates to AV node then ventricles but there’s a reentrant rhtyhm in the left or right atria; loop of depolarization happens on a piece of the tissue

Type 1 typical or Type 2 atypical

type 1 atrial flutter

typical

right sided

moves around tricuspid valve counterclockwise

cavotricuspid isthmus propagates signal more slowly

uses crista terminalis as the electrical barrier

type 1 atrial flutter ECG characteristics

concentric

negative p waves in inferior leads (2,3,aVf)

positive p waves in inferior leads if clockwise

type 2 atypical flutter

reentrant circuit in the right or left atrium

can be left or right sided

scar related

wavefront not travelling around the tricuspid annulus

how is the atrial flutter reentrant circuit initiated?

premature atrial contraction; electrical impulse sent out early in the atrium

atrial flutter side effects

prolonged tachy, atria not contracting properly causing blood clots, heart failure, stroke

treatment for atrial flutter

anticoagulants, beta blockers or calcium channel blockers, RF ablation of cavotricuspid isthmus

electrophysiologic prop of atrial flutter

• Increase in intra-atrial conduction delay

• •

  No rate dependent shortening of AERP

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  Usually the faster you pace atrial tissue the faster it conducts and recovers

  • •

    These changes increase the potential for a reentrant rhythm in the atria

what kind of tachycardia is an atrial flutter

macroreentrant atrial tachy

macroreentrant atrial tachy properties

• Large circuit

•  Area of slow conduction and 

•  Zone of unidirectional conduction block

• Rate is seen between 220-350 beats/min

• Usually requires rapid atrial pacing at 20-50% faster CL than TCL at several seconds to terminate

  • Atrial flutter if left unresolved can degenerate to AFIB over time

macroreentrant atrial tachy ECG properties

• Sawtooth P waves in leads 2 and 3

• Regular R-R intervals

• Typically, 2:1 or 3:1 atrial to ventricular conduction blocks

top to bottom

line of crista terminalis

TV

CS

IVC

isthmus and zone of slow conduction

eustachian valve and ridge

left to right

duodecapolar cath placed in the RA anterior to the crista terminalis

CTI line > path of ablation cath from the tricuspid valve to the IVC

ablation cath on CTI line

RV cath for vent pacing

CS cath for atrial pacing

atrial flutter on an intracardiogram

The first atrial signal is at the proximal CS catheter (not shown), followed by the HIS catheter. The atrial signal is next seen in the duo-decapolar catheter beginning in the HRA and ending in the lower right atrium, following a counterclockwise pattern. This type of typical flutter is called a counterclockwise flutter.

It is important to confirm a _______ blockfor a successful CTI ablation.

bidirectional

entrainment in atrial flutter

1. Pace at a rate 10-20 msec faster than TCL

2. Confirm capture

3. Off pacing, tachycardia must resume

4. If PPI – TCL < 30 msec, then we are within circuit of flutter; calculate on pacing lead

purpose for entrainment in atrial flutter

• The ability to accelerate the tachycardia to the pacing cycle length without changing the tachycardia wave pattern on surface ECG.

• If the tachycardia appears different or the  post pacing interval PPI is longer than tachycardial cycle length during entrainment you are not within the circuit.

PPI (post pacing interval)

• Once pacing is stopped, the tachycardia returns to the baseline tachycardia cycle length.

  • The time it takes to make one revolution around the flutter circuit is considered the PPI. If you are within the circuit, the PPI is equal to or less than 30 ms in reference to the Tachycardia Cycle Length (TCL).

right atrial non-isthmus dependent flutter (location and reentry loop type)

• Lesional Right Atrial Macroreentrant Tachycardia

  • Upper Loop Reentry

left atrial macroreentrant tachycardia (location, circuit structures)

• Mitral Annulus (Perimitral) Atrial Flutter

• Circuits Involving the Pulmonary Vein(s) with or Without Left Atrial Scar

• Left Septal Circuits

Lesional Right Atrial Macroreentrant Tachycardia (location and cause)

These macroreentrant circuits arise around a low-voltage area, incision, patch or scar in the lateral or posterolateral RA.

These areas usually develop after atriotomy and surgery for congenital disease. 3D activation mapping is an excellent modality to identify this type of AFL circuits.

wave morphology for left sided atrial flutter

A positive flutter deflection in the anterior  precordial leads (V1, V2, V3, V4)suggest a  left-side flutter

atrial tachycardia

an arrhythmia which can be caused due to both Focal and reentrant triggers

atrial tachycardia characterisitcs

• Triggered, automatic, or micro-reentry

• Common sites: Crista terminalis, tricuspid valve, CS Os, and pulmonary veins

• P waves visible preceding QRS, but can be hidden within T wave if 1:1

• P wave morphology differs from sinus morphology depending on where it’s originating from

• AV block does not affect tachycardia

• Can be multifocal AT with different P wave morphologies

how is atrial tachycardia induced?

atrial extra stimulus or incremental pacing

what does the VA-AV response to entrainment in atrial tachycardia mean?

• The circuit is entirely within the atrium & does not involve the ventricle at all, so AV block does not affect it either.

left is sinus rhtyhm and right is atrial tachycardia

ablation strat for atrial tachy

• Target earliest site of activation

• Might speed up during Rf delivery & then terminate

• ENDPOINT:

  • Termination of tachycardia

    • Non-inducible with pacing & drugs 

basics of entrainment

patient must be in tachy to use entrainment

pace 10-20ms faster than tachycardia cycle length

stop pacing, ensure patient is still in tachy, then do PPI and TCL measurements

slow fast AVNRT morphology

P wave is usually not visible. This is due to the simultaneous activation of the atria and ventricles. 

QRS morphology during AVNRT is usually the same as in NSR.

slow slo AVNRT morph

Retrograde P wave will appear inverted in the inferior leads and occur after the QRS complex. This is due to retrograde conduction

fast slow AVNRT morph

retrograde P wave is inverted in the inferior leads and will appear before the QRS complex.

CTI is bounded by

tricuspid annulus, CS, eustachian ridge, and IVC