EP studies Flashcards
Normal HV interval
35-55ms
Short HV indicates
AP
HV usually 0 or can be negative
Long HV indictes
infra-HIS disease
Normal AH interval
50-120ms
Long AH indicates
AV block
AH is
time travelled through AVN
HV is
exit from AVN to entrance of HIS system
HV is measured on
H on HIS channel and earliest V on HIS channel
*alternate - His on CS and Earliest V on surface ECG
AH is measured on
A and H on His channel
First test in EP study
IVP (incremental ventricular pacing)
Order of tests in EP study
IVP
Retrograde curve
IAP
Antegrade curve
Ventricular testing stop point
Wenckebach point or 300ms
Principle observations of ventricular testing during EP study (SR)
- Wenckebach point – cycle length at which 1:1 VA conduction stops
- Pattern of retrograde atrial activation
Eccentric (up another way other than AVN)
Concentric (up AVN) - Timing of retrograde atrial activation (if any)
Fixed = AP
Decremental = AVN
e.g. What is dominant in retrograde conduction - AVN or AP (if present)
(if AVN first, then when AVN becomes refractory does AP conduct retrogradely?; if AP first, then what rate does AP become refractory – does it change after ablation?)**
Principle observations of atrial testing during EP study (SR)
- Antegrade conduction properties of AVN and HIS purkinje system
- Wenckebach point – cycle length at which 1:1 conduction over AVN stops
- AH jump = dual nodal physiology (curve)
- Ventricular pre-excitation via AP (increase of pre-excitation)
- Arrhythmia induction
- antegrade pathway conduction rate >240ms unsafe
Diagnosis of PSVT depends on what 3 elements?
a. baseline findings prior to tachycardia initiation
b. tachycardia characteristics
c. tachycardia response to atrial and ventricular pacing manoeuvres
Testing during tachy:
What is entrainment?
Vp at a cycle length 20ms faster than ongoing tachy. Stop pacing and ensure tachy continues after pacing terminates.
Measure first captured V stim to stim and compare to last A-A to see atrial rate now matches Vp rate.
Testing during tachy:
Determine response to entrainment
VAAV - AT
VAV - AVNRT or AVRT
Pseudo VAAV - atypical AVNRT or ORT with slow conducting pathway
What does the VAAV entrainment response mean?
AT - both antegrade and retrograde conduction occurs via AVN so last entrained atrial beat hits a refractory AVN
What does the VAV entrainment response mean?
AVNRT or AVRT - entrainment of atrium due to retrograde conduction over the ascending limb of AVNRT (regardless of type of AVNRT) or up the AP i.e. ORT then antegrade down the AVN
Testing during tachy:
What does it mean if tachy terminates during entrainment?
- Termination of tachy without affecting the atrium excludes AT i.e. end with a V
- Tachy ends with A – likely AVRNT or AVRT
Testing during tachy:
What is HIS sync VPBs?
Vp delivered at a time that the HIS is refractory during SVT.
The only way for the Vp impulse to continue is via an AP as conduction up the AVN is blocked.
Testing during tachy:
Explain response to HIS sync VPBs
- No change in AA timing – **excludes right sided AP **
- Atrial advancement with resetting (with same atrial activation) – AP present and contributes to SVT mechanism = ORT
- Atrial advancement without resetting (with same atrial activation) – **AVNRT with bystander AP **
- Atrial advancement with different atrial activation sequence - bystander AP
- Atrial post excitation – **decrementally conducting AP (Mahaim) and ORT **
- Termination of SVT – **ORT **
Testing during tachy - HIS sync VPBs :
No change in AA timing means?
if AA changed, the only way for it to reach atrium that quickly would be because of an AP that conducts retrogradely = exclusion of right sided AP
Testing during tachy - HIS sync VPBs :
Atrial advancement with resetting means?
next A is advanced, which subsequently advances next HIS and V = AP that contributes to SVT mechanism is present i.e. ORT
Testing during tachy - HIS sync VPBs :
Atrial advancement without resetting means?
no reset means next A is advanced but doesn’t advance next HIS and V = AVNRT with bystander AP
Testing during tachy - HIS sync VPBs :
Atrial advancement with different atrial activation sequence means?
e.g. from concentric to eccentric or 9-10 first to 5-6 first = bystander AP
Testing during tachy - HIS sync VPBs :
Atrial post excitation means?
delay of next A after HIS sync VPB - ORT or decremental AP
Testing during tachy - HIS sync VPBs :
Termination of SVT
ORT
What is the problem when a wobble is present?
Teating during SVT tachy with wobble (variations in cycle length more than 30ms) is un-useful.
Testing during tachy:
What is post pacing interval (PPI)?
Used to differentiate between atypical AVNRT and AVRT that uses a septal AP.
Testing during tachy:
How is PPI measured?
- Perform entrainment.
- Measure from last Vp beat to first return to tachy i.e. PPI
- Then Measure tachy cycle length after pacing cessation i.e. TCL
- Do PPI – TCL calculation.
If <115ms = AVRT; > 115ms = AVNRT
Testing during Sinus:
What is para-HISian pacing?
Testing used to exclude presence of right sided septal AP
Testing during Sinus:
How is Para-HISian pacing measured?
- Pace at high outputs to get narrow QRS as capturing AVN, HIS and RV.
- Drop outputs quickly to capture only RV (Broad QRS).
- Measure and compare VA intervals of Broad and Narrow complexes.
What does the presence of BBB during tachycardia means?
Does the VA time change?
- AP present, VA will increase during BBB because impulse now has to travel to unblock bundle branch before blocked one, and then back up to atrium to conduct as a circuit.
- no AP present, VA time will remain the same between narrow and blocked beats
What is determined during EP testing?
a) Antegrade and retrograde conduction properties of AVN/AP/ANVRT
b) If present, is AP/AVNRT safe?
c) Allows for SVT?
channel 9-10
In eccentric atrial activation, where is A seen first on the CS channel?
Can be anywhere on CS channel depending on diagnosis and localisation
Ventricular pacing manuvers during Sinus:
How is a retrograde curve performed?
8 beat drive train follwed by extrastimulus with shorter coupling intervals that decrement during decrement until wenckebach point or 300ms.
Why is retrograde testing important for APs?
Majority of AP conduct retrogradely i.e. orthodromic AVRT
Down the AVN up the pathway = Narrow tachycardia
Atrial pacing manuvers during Sinus:
How is incremental atrial pacing performed?
- Start Ap at a rate faster than Sinus cycle length (500 or 400ms)
- Slowly increase the pacing rate (- button) until wenckebach point or 200ms
What does it mean if the on the MAP channels signals on channel 3-4 are seen to be ahead of signals on channel 1-2?
The ablation tip (channel 1-2) has gone past the hot spot
What is the advantage of using adenosine?
Expect VA and AV block which allows for hyperpolarisation of AP if still present before or after ablation
In AVNRT and AVRT what catheter is the reference?
CS catheter
because SVTs of this origin occur near the CS and thus the CS catheter is used to bracket the surrounding area; therefore can be used as a reference i.e. distance from CS catheter to hotpoint.
If looking for AT of different origin (e.g. not close to CS) then reference would be placed elsewhere e.g. HRA
During IVP, VA conduction shows concentric atrial activation with decrement. What does this mean?**
Retrograde conduction up the AVN.
*If AP is present then it does not conduct retrogradely or fused i.e. up the pathway, so down the AVN - Orthodromic (Narrow)
During IAP, conduction shows concentric atrial activation with decrement. What does this mean?
Antegrade conduction down the AVN.
*If AP is present then it does not conduct antegrade or fused i.e. down the pathway, so up the AVN - Antidromic (Broad)
During IVP, VA conduction shows eccentric atrial activation without decrement. What does this mean?
Retrograde conduction up the pathway
*If AP is present then it does conduct retrogradely i.e. up the pathway, and down the AVN - Orthodromic (Narrow)
During IAP, conduction shows eccentric atrial activation without decrement. What does this mean?
Antegrade conduction down the pathway.
*If AP is present then it does conduct antegrade i.e. down the pathway, up the AVN - Antidromic (broad)
Define Eccentric activation
atrial activation other than by AV node during V pacing
or early activation of ventricle during A pacing
Define concentric activation
normal AVN activation of atria
*earliest atrial activation on HIS catheter first
Define VERP
No capture of Ventricles with Vp
Define VAERP
VA conduction becomes refractory
Define AERP
LOC during Ap
Define AVNERP
Define Wenckbach CL
The point at which the AP or AVN becomes refractory during incremental pacing
Purpose of IVP
Discover what retrograde routes connecting ventricles to atria are available for impulse conduction
No VA conduction suggests lack of VA connection via AVN or AP and AT is more likely
During ablation of AVNRT, what ablation catheter and method is used?
Non-irrigated 4mm tip ablation catheter
Nibble method
For less deep burn as close to AVN
A sudden increase in PR interval during PAC or atrial pacing suggests what?
Shift in anterograde conduction from fast to slow pathway (AH jump).
*PAC blocks in refractory fast pathway (reaches its refractory point) but still conducts to AVN via slow pathway
An AH jump is defined as what during an Antegrade curve?
> 50ms increase in AH interval
*An AH jump only proves presence of dual nodal physiology, not definitely prove their SVT is AVNRT
Define AV nodal echo beat
One beat of non-sustained tachycardia caused by anterograde conduction via the slow pathway. and subsequent retrograde activation via the fast pathway
Conventional ablation therapy for AVNRT is what?
slow pathway modification
*aim to disrupt tachycardia substrate by ablating slow pathway and changing conduction properties.
What can indicate the operator is on the wrong site for ablation during AVNRT cases?
HIS signal on ablation catheter (Map)
Ablation of AVNRT is performed during which rhythm?
Sinus Rhythm
*to increase stability of catheter and monitor AV association
What rhythm should be elicited during the first 15s of ablation?
Junctional Rhythm
*Accelerated junctional rhythm >120bpm could suggest ablation of fast pathway or AVN which increases risk of CHB
What targets for ablation can be seen on the Map catheter to indicate good contact with the slow pathway?
Large V signal
Small A signal
No HIS signal
**
Identify the primary endpoints for AVNRT ablation
complete elimination or modification of slow pathway assessed by:
- Presence of slow Junctional rhythm during ablation
- Non inducibility of AVNRT
During retrograde curve, where are u measuring from using the callipers?
Stim to earliest A on CS
During antegrade curve, where are u measuring from using the callipers?
A capture on CS to HIS/earliest V on surface ECG
Differential diagnosis for a wide complex tachycardia with RBBB and long RP in tachycardia
- atypical (fast-slow) AV nodal reentrant tachycardia
- orthodromic reciprocating tachycardia
- atrial tachycardia with an underlying bundle branch block
Identifying AP location:
V1/V6
LBBB = right sided (Bigger S wave in V1)
RBBB = left sided (Bigger R wave in V1)
Identifying AP location:
Transition in chest leads
Early (by V2/V3) = septal
Late (V3 and onwards) = lateral
Identifying AP location:
Inferior leads (aVR, II,III)
All neg = posterior
All Pos = Anterior
Mismatch = midline
In Manifest AP, what direction do they predominantly conduct?
Orthodromic
Orthodromic AVRT has a long or short RP?
short
can be long if accessory pathway is slow
ECG charateristics of Orthodromic AVRT tachycardia
Normal narrow QRS complexes
150-250bpm
Visible P wave (retrograde in inferioe lead and after QRS)
Short RP (long PR)
Antidromic AVRT has a long or short RP?
Long
ECG charateristics of Antidromic AVRT tachycardia
Wide complex QRS (visible delta)
150-250bpm
No visible p wave (but retrograde and before QRS)
Long RP
Adenosine
short acting antiarrhythmic
causes depression of SA and AV nodal acitivty
diagnosis and treatment of paroxysmal SVT
Contraindications of adenosine
second and third degree AV block
allergy
care with asthma and COPD
define concordance
all QRS complexes from Lead V1 to V6 are in the same direction; either all positive or all negative
Any biphasic QRS complexes (qR or RS) means no concordance.
Negative concordance (all negative QRS) suggests?
VT
Positive concordance suggests?
VT or antidromic AVRT
Why should adenosine not be administered for suspected VT?
Andenosine in VT can accelerate the frequency and aggravate the arrhythma.
If suspected SVT and adenosine is administered and the response is no effect or tachy acceleration then likely VT
Identify the 5 criteria of the Brugada algorithm for differentiating VT from SVT.
Is there an absence of an RS complex in all precordial leads?
i.e. - All QRS complexes completely upright or downward in precordial leads
Is the R to S interval >100 ms in any one precordial lead?
i.e. - Distance between R and S waves in each precordial lead >100ms
Is there Atrioventricular dissociation
i.e. - Are p waves seen at different rates than QRS complexes
Is the morphology criteria for VT present in both precordial leads V1-V2 and V6?
i.e. - VT is frequently a RBBB pattern (upright in V1) or LBBB (downward in V1)
If yes to any of these criteria: Ventricular Tachycardia (VT) likely
If “no” to all four of these criteria: Supraventricular Tachycardia (SVT) likely
The original Brugada study found the four criteria together to be 98.7% Sn and 96.5% Sp for detection of VT
Nodal response during Para-HISIAN pacing
VA time remains unchanged between Narrow to Broad QRS (does not exclude left sided pathways)
I.e. no AP present
What is extra-nodal response during Para-Hisian pacing?
VA time is shorter between Narrow to Broad QRS
I.e. Concealed AP present.
Chest leads look at what region of the Heart for AP localisation?
Where it is septal or lateral
V1/V6 indicate right or left sided
Inferior leads reference what area in regards to AP localisation?
Posterior, Anterior, midline
What are the 4 regions of left sided free wall pathways?
Left anterolateral (LAL)
Left lateral (LL)
Left posterolateral (LPL)
Left posterior (LP)
What are the 5 regions that right free wall pathways can arise?
Right anterior (RA)
Right anterolateral (RAL)
Right lateral (RL)
Right posterolateral (RPL)
Right posterior (RP)
Wenchebach CL is found during what tests?
IAP & IVP
ERP is found during what tests?
Curves
Posterior
Back of heart
Anterior
Front of heart
Superior
Top
Inferior
Bottom
No VA conduction during retrograde testing suggests?
No retrograde conduction - either no AP present or AP conduction is sluggish
AVNRT ablation catheter
Navistar non irrigated
End point criteria for AVNRT slow pathway ablation
No jump
No echo
Slow pathway block
What are the characteristics of automatic tachycardias?
Warm up and cool down in rate
Metabolic causes e.g. ischemia, hypoxemia, hypokalemia
Name a type of automatic tachycardia
Atrial tachycardia
Name a type of tachycardia that is considered to be re-entry and why
AVNRT
because it meets the criteria of re-entry tachycardias with 2 pathways connected proximally and distally that have different conduction and refractory properties
What is triggered activity
A leakage of positive ions into the cardiac cell causing a bump in phase 3 or 4 of the cardiac action potential = after depolarisation.
If they are big enough to engage the rapid sodium channels another action potential can be generated
Long RP tachycardia
ORT
Atypical AVNRT
Repetitive V response
critical coupling intervals during ventricular extrastimulus testing (S2) can be followed by ventricular responses similar in morphology and axis to the paced beat.
RVOT paced morphology on ECG
LBBB (in chest leads all negative)
Positive inferior leads (avL negative)
RV apex paced morphology
LBBB in chest leads (all negative)
Negative in inferior leads (avL positive)
LBBB during ORT means what?
Left sided AP - longer VA
Right sided AP - Same or short VA
RBBB during ORT
Left sided AP - same or short VA
Right sided AP - longer VA
Ablation settings for AVNRT
30-35 degrees
50-55 degrees
When to tell operator to stop during AVNRT ablation
Getting close to AVN
Too many ablation points with no true junctional response
What is the underlying mechanism for Sustained monomorphic VT during VT stim?
Ischemic heart disease with old scar that forms a substrate for re-entry VT.
What is the underlying mechanism for Polymorhic VT and VF?
focal mechanism such as triggered or enhanced automaticity.
Mechanisms of Ventricular arrhythmias
Automatic ventricular arrhythmias
PVCs
Acute medical conditions - acute MI, electrolyte imbalance, increased sympathetic tone
Mechanisms of Ventricular arrhythmias
Re-entrant ventricular arrhythmias
PVCs
Chronic heart disease - previous MI, cardiomyopathy (ARVC)
Mechanisms of Ventricular arrhythmias
Triggered activity
Pause dependent triggered activity
Catechol dependent triggered activity
Mechanisms of Ventricular arrhythmias
Miscellaneous ventricular arrhythmias
Idiopathic LV tachycardia
Outflow tract ventricular tachycardia
Brugada syndrome
CPVT
How do re-entrant circuits arise in ischemic heart disease?
during healing and ventricular remodelling that follow acute MI
Usually form on the border zone between scar tissue and normal healthy tissue
How do you reveal a pathway?
- Adenosine - disable the AVN
- Ap fast enough to cause decrement in the AVN to allow AP to beat it and conduct first
- pace closer to the pathway
How do you pace close to an AP without moving a catheter or using a RA catheter?
Pace from different poles on the CS.
9-10 to pace the right side of the atrium (RA)
5-6/7-8 for septal
1-2 to pace left side of atrium (LA)
PPI for right sided pathways short or long?
Short usually 30-40ms because the tachy is within the RV circuit?
In AP pathways, how is conduction through the pathway measured?
Using the VA time at the site of earliest retrograde atrial activation
I.e. Earliest A on CS
In AP pathways, how is conduction through the pathway measured?
Using the VA time at the site of earliest retrograde atrial activation
I.e. Earliest A on CS
A n increase in VA time after Vp is diagnostic of what?
A free wall bypass tract
e.g. RVp in a patient with left sided pathway had increase in VA time but no change with a septal pathway bcecause VP impulse goes from purkinje to RBB then LBB so VA time increases but septal pathway Vp impulse goes from Purkinje to pathway so no change in VA time
Rarely, an increase in VA time after Vp is diagnostic of what?
A free wall bypass tract
e.g. RVp in a patient with left sided pathway had increase in VA time but no change with a septal pathway bcecause VP impulse goes from purkinje to RBB then LBB so VA time increases but septal pathway Vp impulse goes from Purkinje to pathway so no change in VA time
If the AP is slanted or Oblique why would VA time change during Vp?
Because you are pacing from V, it is now a different activation wavefront from the ventricular insertion of the AP causing change in VA time.
In AVRT and AVNRT, VA times during at rapid paced rates should be what?
Short and fixed
