Hany S. Abed B . P h a r m a c y , M B B S , P h D , I B H R E C e r t i f i e d E P a n d C a r d i a c D e v i c e s S p e c i a l i s t
C l i n i c a l C a r d i a c E l e c t r o p h y s i o l o g y F e l l o w L o y o l a U n i v e r s i t y M e d i c a l C e n t e r
Techniques for Differentiating Supraventricular Tachycardias
Concepts and Cases
April 25th 2014
Outline
Induction of tachycardia
Baseline tachycardia features
Diagnostic maneuvers during tachycardia
Diagnostic maneuvers in sinus rhythm after
tachycardia termination
Induction of Tachycardia
Initiation by AES or atrial pacing
Requirement of AV conduction delay
Warm-up
VA interval
Initiation by VES or ventricular pacing
HA interval
Initiation by AES or Atrial Pacing: Requirement of AV Conduction Delay
SVT initiation that is reproducibly dependent on a
critical AH interval:
Classic for typical AVNRT
Not always obvious with atypical AVNRT
May be present in AT but not a prerequisite
ORT often associated with AV delay but anterograde block in
the AAVC is key
Initiation by AES or Atrial Pacing: Requirement of AV Conduction Delay
Initiation by AES or Atrial Pacing
Warm-up
Characteristic but not exclusive of automatic AT
VA linking at induction
Compare VA interval of first tachycardia beat to the rest of SVT
If reproducibly identical, AT is very unlikely
Initiation by VES or Ventricular Pacing
His Bundle-Atrial interval
Compare HA interval during during SVT with the HA interval occurring after a VES that results in an H-H interval similar to H-H during SVT
AVNRT
HASVT < HAVES
AVRT
HASVT > HAVES
Baseline Tachycardia Features
Atrial activation sequence
Eccentric vs. Concentric
Is earliest “A” near AV rings?
Baseline Tachycardia Features: PR/RP relationship
AT
PR interval usually longer than during SR
The faster the AT, the longer the PR interval
PR interval can be >, < or = to RP
Watch out for PR=RR resulting in P falling within QRS (AVNRT)
Typical AVNRT: VA typically -40 to 75 msec
Atypical AVNRT: long RP tach
PR and AH intervals often shorter than during SR
ORT: usually short RP but VA > 70 msec
Baseline Tachycardia Features: AV block
Baseline Tachycardia Features: AV block
Where is the block?
Baseline Tachycardia Features: AV block
Baseline Tachycardia Features: Oscillation in the TCL
SVT CL variability of ≥15 msec occurs in 73% of PSVT
Equally prevalent in AT, ORT, AVNRT
Changes in atrial CL precede and predict changes in ventricular CL
AT or atypical AVNRT
Changes in ventricular CL precede and predict changes in atrial CL
Typical AVNRT or ORT
Baseline Tachycardia Features: Oscillation in the TCL
Baseline Tachycardia Features: Oscillation in the TCL
Baseline Tachycardia Features: Oscillation in the TCL and P-QRS
Variations in P-QRS relationship (AH, HA, AH/HA
ratio) especially at initiation or termination of SVT
Should not be misdiagnosed as AT
Often seen in atypical AVNRT
May be seen in typical AVNRT
Spontaneous changes in PR (AH) or RP (HA)
intervals with fixed A-A favor AT and exclude AVRT
Baseline Tachycardia Features: Oscillation in the TCL and P-QRS
Baseline Tachycardia Features: Effects of Bundle Branch Block
LBBB aberrancy during SVT is suggestive of ORT
BBB during SVT that does not prolong the VA (HA) interval excludes ORT using ipsilateral AAVC
May still be AVNRT, AT or ORT using contralateral AAVC
Prolongation of VA interval with BBB > 35 msec indicates ORT with ipsilateral free wall AAVC
Prolongation of VA interval < 25 msec suggests ORT utilizing a septal AAVC
Baseline Tachycardia Features: Effects of Bundle Branch Block
Outline
Induction of tachycardia
Baseline tachycardia features
Diagnostic maneuvers during tachycardia
Diagnostic maneuvers in sinus rhythm after
tachycardia termination
Diagnostic Maneuvers During Tachycardia
AES during tachycardia Resetting
Termination
Atrial pacing during tachycardia Entrainment
Δ AH
Acceleration
Overdrive suppression
Termination
Differential site atrial pacing
VA interval in return cycle following cessation of pacing
Atrial Extrastimulation During SVT: Resetting
AES can reset AT, AVNRT and ORT
Resetting with manifest atrial fusion
May be seen in ORT and macroreentrant AT
Not seen in AVNRT or focal AT
Atrial Pacing During SVT: Entrainment
Overdrive atrial pacing can entrain macroreentrant
AT, AVNRT and ORT
Automatic or triggered AT cannot be entrained
Entrainment with manifest fusion in ORT or
macroreentrant AT (similar to AES concept)
VA linking
Compare postpacing VA interval to SVT VA interval
Atrial Pacing During SVT: Entrainment
Atrial Pacing During SVT: Overdrive Suppression
Return CL following the pacing train prolongs with
increasing duration and/or rate of pacing train
Suggests automatic AT
Entrained reentrant circuits have constant return
cycles regardless of the length of pacing drive
Warm up may be seen in automatic AT after
cessation of atrial pacing
Atrial Pacing During SVT: Differential-Site Atrial Pacing
Atrial Pacing During SVT: Differential-Site Atrial Pacing
Δ VA < 14 msec = ORT/AVNRT
Atrial Pacing During SVT: Differential-Site Atrial Pacing
Δ VA > 14 msec = AT
Atrial Pacing During SVT: Differential-Site Atrial Pacing
Diagnostic Maneuvers During Tachycardia
VES during tachycardia
Resetting (His refractory VES, Preexcitation index)
Termination
Ventricular pacing during SVT
Atrial activation sequence
Entrainment
AV vs AAV response
Termination
VES During SVT: His Refractory VES
VES delivered during SVT when the His potential is already manifest or within 35 to 55 msec before the time of the expected His potential
Advancing the next A +/- termination of SVT
Confirms presence of retrogradely conducting AAVC
Excludes AVNRT but not AT with bystander AAVC
Advancing the next A with activation sequence identical to SVT favors ORT over AT with bystander
VES During SVT: His Refractory VES
VES During SVT: His Refractory VES
Delay of the next A = ORT
Decremental conduction over AAVC
An innocent bystander AAVC cannot delay A during AT
Termination of SVT without an A = ORT
VA block in the AAVC
Note, even a well timed His refractory VES may not affect the next atrial activation if the stim is far from the site of the AAVC
VES During SVT: His Refractory VES
VES During SVT: His Refractory VES
VES During SVT: Preexcitation Index
Preexcitation index: VES usually reset ORT
Distance between stim and ventricular insertion of AAVC
VES coupling interval (Preexcitation index)
PI > 75 msec suggests left free wall AAVC
PI < 45 msec suggests septal AAVC
The inability of single or double VESs to reset SVT despite advancement of all ventricular EGMs (including local V in EGM with earliest A) by > 30 msec excludes ORT
VES During SVT: Preexcitation Index
VES During SVT: Preexcitation Index
AVNRT or ORT
Ventricular pacing during AVNRT and ORT reaches the atrium over the tachycardia retrograde limb
Atrial activation sequence during SVT = Retrograde atrial activation with V pacing during SVT
AT
Atrial activation during AT ≠ retrograde atrial activation with V pacing
Pitfall: AT originating close to AVJ
Beware bystander AAVC with retrograde conduction resulting in retrograde atrial activation during V pacing ≠ SVT even if due to AVNRT or ORT
Ventricular Pacing During SVT: Atrial Activation Sequence
Ventricular Pacing During SVT: Entrainment
PPI – TCL and SA – VA
Original paper evaluated 30 patients with atypical AVNRT and 44 patients with ORT using a septal AAVC
Same criteria apply to typical AVNRT
For borderline values pace RV base instead of apex
PPI-TCL will be exaggerated in AVNRT (farther from circuit)
No significant change in ORT (still in the circuit for septal AAVCs)
PPI - TCL and SA - VA
AVNRT
PPI - TCL = 150 msec SA – VA = 120 msec
*S-A measured from last pacing stimulus to HRA
PPI - TCL and SA - VA
ORT
PPI - TCL= 80 msec SA – VA = 40 msec
*S-A measured from last pacing stimulus to HRA
PPI - TCL and SA - VA
Corrected PPI - TCL
Traditional vs. Corrected PPI - TCL
Manifest Ventricular Fusion During Entrainment
Analysis of Transition Zone During Entrainment
Not dependent on tachycardia continuation after RVP
His bundle recording is unnecessary
AVNRT was identified with PPV and NPV of 100% using criteria of > 1 QRS of fixed morphology to accelerate TCL to PCL
A cut-off of ≤ 1 QRS of fixed morphology resulting in acceleration of TCL to PCL had a PPV and NPV of 100% for identifying ORT
“Transition Zone” concepts: • AVRT circuit is large • AVNRT circuit is small • It is easier to get into the AVRT
circuit when pacing from the RV apex
• You will fuse and manifest into
the QRS quickly as you entrain the atrium in AVRT
• You will require more
progressive fusion of the QRS (less quickly) as you entrain the atrium in AVNRT
• Advantage is it is independent
of SVT termination after VOP • Need to look at all 12 ECG
leads
Fixed
morphology
RVP beats
required to
accelerate
TCL to PCL
Analysis of Transition Zone During Entrainment
Ventricular Pacing During SVT: A-V vs. A-A-V Response
A-V = AVNRT or ORT
Antegrade limb not refractory so able to conduct to V
A-A-V = AT
Antegrade limb (AVN) refractory since just used retrograde
Must confirm entrrainment before applying
Pseudo A-V and Pseudo A-A-V
A-V Response
A-A-V Response
Pseudo A-V Response
Pseudo A-V Response
Pseudo A-A-V Response
AAV or AV Response?
Diagnostic Maneuvers in NSR After SVT Termination
Atrial pacing at TCL
ΔAH interval
AV block
Ventricular pacing at TCL
ΔHA interval
VA block
Atrial activation sequence
Differential RV pacing
Parahisian pacing
Atrial Pacing at TCL: ΔAH Interval
AT/ORT
AH during SVT comparable to during A pacing at TCL due to similar activation
AVNRT
AH during SVT shorter than during A pacing at TCL due to different activation (parallel vs. series)
Δ AH (AHatrial pacing at TCL - AHSVT)
> 40 msec suggests AVNRT
< 20 msec suggests AT or ORT
Atrial Pacing in Sinus Rhythm at TCL: ΔAH interval
Atrial Pacing in Sinus Rhythm at TCL: ΔAH interval
Atrial Pacing in Sinus Rhythm at TCL: ΔAH interval
Atrial Pacing in Sinus Rhythm at TCL: AV block
AT/ORT
Atrial pacing at the TCL should result in 1:1 AV conduction
Should test shortly after SVT termination to maintain similar autonomic tone
The development of AV block with atrial pacing at TCL is consistent with AVNRT
Upper common pathway block
AVNRT
HA activated in parallel during SVT and in series during ventricular pacing
HA during SVT shorter than during ventricular pacing at TCL
ORT
HA activated in series during SVT and in parallel during ventricular pacing
HA during SVT is longer than during ventricular pacing at TCL
Δ HA (HAV pacing at TCL – HASVT) more negative (<) than -10 msec = ORT
Δ HA > -10 msec = AVNRT
Ventricular Pacing in Sinus Rhythm at TCL: ΔHA interval
Ventricular Pacing in Sinus Rhythm at TCL: ΔHA interval
Ventricular Pacing in Sinus Rhythm at TCL: ΔHA interval
Ventricular Pacing in Sinus Rhythm at TCL: ΔHA interval
Ventricular Pacing in Sinus Rhythm at TCL: ΔHA interval
Greg Michaud et al
Ventricular Pacing in Sinus Rhythm at TCL: VA Block
VA block during ventricular pacing makes ORT with a fast retrograde AAVC unlikely
More likely in setting of VA block
AT
AVNRT with lower common pathway block
PJRT
Ventricular Pacing in Sinus Rhythm at TCL: Retrograde Atrial Activation Sequence
AVNRT
Atrial activation sequence usually similar during AVNRT and ventricular pacing in NSR
ORT Retrograde VA conduction during ventricular pacing may proceed
over the AVN, the AAVC, or both
Atrial activation sequence may be similar or different during ORT and ventricular pacing in NSR
AT
Atrial activation during AT ≠ retrograde atrial activation with V pacing
Pitfall: AT originating close to AVJ
Maneuvers in NSR After SVT Termination: Differential RV Pacing
Compare VA interval and atrial activation sequence with pacing from RV base vs. RV apex
(-) Retrogradely conducting septal AAVC
Shorter VA interval when pacing from the apex
Same atrial activation sequence
(+) Retrogradely conducting septal AAVC
Shorter VA interval when pacing from base
Atrial activation sequence can be same or different depending on degree of contribution of AVN and AAVC
Pitfalls
Doesn’t exclude free wall AAVC or slowly conducting AAVC
Maneuvers in NSR After SVT Termination: Differential RV Pacing
Maneuvers in NSR After SVT Termination: Differential RV Pacing
2
Maneuvers in NSR After SVT Termination: Parahisian Pacing
Ventricle and HB capture
Relatively narrow QRS
S-A interval = HA interval (direct His capture)
Only ventricular capture
Wide QRS, LBBB
S-A = S-H interval + HA interval
Maneuvers in NSR After SVT Termination: Parahisian Pacing
Maneuvers in NSR After SVT Termination: Parahisian Pacing
Maneuvers in NSR After SVT Termination: Parahisian Pacing
Case 1: Which arrhythmia mechanism can be excluded?
Case 2: What arrhythmia mechanism can be confirmed?
Cases 1 and 2: Coumel and Reverse Coumel
BCT LBBB and NCT, VA association, eccentric CS activation, no change in CL or VA time with
change from LBBB to NCT
Case 3: What is the diagnosis and why?
Case 3: Tachycardia termination
• NCT with A>V. Short VA time
• Cannot be AVRT
• AT or AVNRT (“atypical”)
• His refractory PVC terminates the
tachycardia without affecting the
atrium
• Can only be AVNRT with block below
the final common pathway
Case 4: Describe the following?
Case 5: Describe the following?
Case 4 and 5: Para-His bundle pacing?
• No pathway: High output captures His and
myocardium via HPS
• No pathway: Low output captures septum
myocardium, travels to distal HPS to invade
retrograde
• Pathway present:
High output captures
His and pathway
(short-cut to atrium)
• Pathway present:
Low output captures
pathway and septum
myocardium (short-
cut to atrium)
Case 4 and 5: Para-His bundle pacing elaborated
Case 6: Which tachycardia mechanism is ruled out?
Case 6: Tachycardia termination
Eccentric activation of the coronary sinus catheter suggests left lateral AP
However AVNRT utilising a leftward nodal extension cannot be excluded
• PVC terminated the
tachycardia without an early
(“pulling in”) atrial
electrogram
• Indicates the SVT is AVN
dependent – thus ruling out
FAT
• Note subtle delay in atrial
electrogram – suggests
decremental retrograde
conduction
Case 6: PVC during SVT
Case 7: Which tachycardia mechanism does the following
maneuver “rule-in”?
Case 7: Which tachycardia mechanism does the following
maneuver “rule-in”?
• Note the PAC is delivered away from the septum. Being able to perturb the circuit far away
from the septum suggests a wide excitable gap.
• Compare that to AVNRT or Nodoventricular/Nodofascicular accessory pathway, which
have a narrow excitable gap
• If AVNRT with bystander accessory pathway: A His refractory PAC will advance next V,
BUT not “pull-in” the subsequent A.
• This is an antidromic AVRT using an AV
accessory pathway
• Delivering a PAC during His bundle
refractoriness advances the ventricle
• QRS morphology remains identical
Case 8: What is the most likely tachycardia mechanism?
Case 8: What is the most likely tachycardia mechanism?
• Pacing during sinus rhythm from the His bundle region does not conduct in the retrograde direction to the atrium.
• This makes AVRT very unlikely,
AVNRT unlikely. AT is most likely
The End
H a n y S . A b e d B . P h a r m a c y , M B B S , P h D , I B H R E C e r t i f i e d E P a n d C a r d i a c D e v i c e s S p e c i a l i s t
C l i n i c a l C a r d i a c E l e c t r o p h y s i o l o g y F e l l o w
L o y o l a U n i v e r s i t y M e d i c a l C e n t e r
A p r i l 2 0 1 4
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