Basics EPS Flashcards
Formula for Sinoatrial Conduction Time
(Basic Cycle Length - return interval) / 2
Normal sinoatrial conduction time
<120msec
Normal AH interval
55-150
Normal HV interval
35-55
Normal sinus node recovery time (uncorrected)
<1500ms
At what sinus node recovery time should pacing be considered?
> 2500ms
Formula for corrected sinus node recovery time?
SNRT - BCL
What is a normal corrected sinus node recovery time?
350-550ms
What is a normal PA interval?
25-55msec
What does the PA interval measure?
Intra-atrial conduction
At what HV interval is there a significant risk of progression to 2nd or 3rd degree heart block?
HV of >100ms
Normal AV nodal WCL?
350-500
Normal AVN ERP?
250-400
Normal HIS bundle spike duration?
<30msec
What is the rate of PPM requirement over 1 year with a HV interval >100msec?
25%
How do you define the HIS bundle ERP?
Longest h1-h2 not followed by a V2
How do you calculate HIS Bundle ERP?
H1-h2
What’s a normal HIS bundle ERP?
<400
What are the three pathophysiologic mechanisms of arrythmia?
- Automaticity
- Triggered Activity
- Re-Entry
What is the formula for determining you are within the circuit after successful entrainment?
PPI - TCL is <20msec
If SVT is inducible by V pacing what does that suggest?
Less likely atrial tachy, more likely AVNRT/AVRT
If AV nodal block stops tachycardia, what does this indicate?
AV nodal dependent tachycardia (AVNRT or AVRT)
How does assessing retrograde atrial activation assist in determining accessory pathway location?
Can assist in determining left or right sided. Earliest CS1-2 left sided. Earliest HRA, right sided.
During tachycardia, AV block with no change to SVT indicates what?
Excludes AVRT
What happens to VA time during bundle branch block with an ipsilateral accessory pathway.
VA time prolongs
Free wall pathway is suggested with what VA time prolongation with ipsilateral bundle branch block?
> 30msec
Septal accessory pathway is suggested with what change in VA time with ipsilateral bundle branch block?
<30msec
What happens with VA time with AVNRT during a bundle branch block?
No change
After atrial entrainment, what happens to the VA time in AVNRT and AVRT.
No change
After atrial entrainment, what happens to VA time in atrial tachycardia?
VA time prolongs
During Ventricular entrainment, what happens to atrial activation in AVNRT/AVRT?
No change
During ventricular entrainment, what happens to atrial activation during atrial tachy?
Atrial activation changes
What response is expected after ventricular entrainment with an AV nodal dependent tachycardia?
VAV response
What response is expected after ventricular entrainment with an atrial tachycardia?
VAAV response
What features do you look for after successful ventricular entrainment to determine type of SVT?
- Atrial activation pattern
- VAV or VAAV response
- VA time post pacing
- Number of fully captured beats until entrainment
- Response to VA dissociation if occurs
If the tachycardia terminated with burst ventricular pacing through AV block, what does this suggest?
AV nodal dependent tachycardia
What do you look for with a HIS refractory PVC in AVRT?
Advancement of the A
What Lead 2 R wave peak time is indicative of VT with a 99% specificity and a 93% sensitivity? (Excluding fascicular VT and antidromic SVT)
> 50msec
What happens to the QRS morphology with atrial entrainment during VT?
Narrower QRS due to fusion/capture
What happens to the QRS morphology with atrial entrainment with SVT with a wide complex?
No change to wide QRS morphology
What A2-H2 jump defines dual AV nodal physiology when performing atrial extra stimulus testing?
> 50msec
What is the tachycardia zone of AVNRT when performing EPs?
Fast pathway ERP - Slow pathway ERP
What is the definition of crossover?
When the Atrial paced PR interval is longer than the Atrial paced cycle length
What VA time would you expect in typical AVNRT?
<70msec
What are the EPS features of typical AVNRT?
- VA time <70
- AH time >200
- Earliest retrograde A in His
- V pacing with A entrainment has same pattern
- VAV response after entrainment
- No atrial advancement with HSPBC
- Evidence of dual AV nodal physiology
- VA block with SVT continuation
- > 1 fully paced beat to reset the cycle length
What are the EPS features of atypical fast slow AVNRT
- Dual AV nodal physiology
- VA block with SVT continuation
- Septal VA time >70msec
- AH <200
- AH <HA during tachycardia
- Earliest atrial signal in CS os
- V pacing with A entrainment has same activation pattern
- VAV response post entrainment
- No A advancement with HSPVC
- More than 1 fully paced beat to reset cycle length
Name the three different types of AVNRT and there characteristic difference on EPS
- Typical slow fast AVNRT
- VA time <70
- AH > HA
- earliest A in His - Atypical fast slow AVNRT
- VA time >70
- AH < HA
- earliest A in CS - Atypical slow slow AVNRT
- VA time >70
- AH > HA
- earliest A in CS
How do you differentiate between typical AVNRT and Junctional Tachycardia?
Atrial entrainment during tachycardia and assess return cycle. If VAV then it’s AVNRT, if VAAV then it’s Junctional Tachycardia
EP characteristics of a concealed accessory pathway?
- Eccentric CS activation with V pacing
- Fixed VA time (no decremental properties) during V pacing
Baseline EPs characteristics of an antegrade accessory pathway?
- Delta wave
- Short HV interval <35ms (can be negative)
- Shortening of the HV with incremental antegrade pacing
- Accentuation of pre excitation with increasing atrial pacing rates (widening of the QRS)
- Accentuation of pre excitation when pacing closer to the pathway
- Eccentric ventricular and atrial activation
- Non decremetal pathway block
What cycle length for 1:1 conduction defines a benign pathway?
> 300msec
What are the EPS signs of multiple accessory pathways?
- Changing delta waves
- Multiple routes of retrograde atrial activation
- Orthodromic tachy with intermittent ante-grade tachycardia
- Discontinuous atrial activation sequence
- Eccentric atrial activation during antidromic AVRT
EPS characteristics of Orthodromic pathway SVT
- Eccentric retrograde A activation
- VA time >60msec
- Ipsilateral BBB will increase VA (free wall >30, septal <30)
- Atrial advancement with HIS synchronous PVCs
- No change in VA cycle length after successful atrial entrainment (AVNRT or AVRT)
- Same atrial activation during Ventricular entrainment (AVNRT or AVRT)
- VAV response after entrainment from Ventricle
- No VA dissociation
- Successful entrainment within 1 beat
HSPVS should advance the atrium during tachy in those with an retrograde accessory pathway. What is the exception?
- Left lateral pathways. May conduct through the AV node prior to reaching the pathway
How do you differentiate between Septal AVRT and AVNRT?
- Apex base pacing.
- PPI - TCL
- Beats required to entrain during V pacing
- Adenosine
Expected apex/base pacing response with accessory pathway?
Shorter VA with basal pacing.
Longer VA with apex pacing
Expected PPI-TCL with RV apex entrainment with accessory pathway?
PPI-TCL = <115 (PPV 86%)
Ventricular entrainment, expected PPI-TCL with AVNRT?
PPI-TCL = >115msec
High power short duration ablation produces what kind of lesion (when compared to low power long duration?)
Wider, shallow lesions