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EP > Diagnostic EP Maneuvers > Flashcards

Diagnostic EP Maneuvers Flashcards

1
Q

What is the “Absolute Refratory Period”?

A

Generaly describes behavior at the single cell level - the period of time after depolarization when the cell in incapable of being activated. Generally describes the lack of availability of functional Na+ channels. Not generally used in clinical EP

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2
Q

What is the “Relative Refractory Period”?

A

This also can be applied to single cell prep but also at a macro tissue scale. In clincal terms, the relative refractory period is the longest coupling interval that prolongs conduction relative to the basic drive train. For example: the relative refractory period of the atrium is the longest S1-S2 that prolonges the S2-A2 relative to the S1-A1.

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3
Q

What is the “Functional Refractory Period” (FRP)?

A

The FRP is the shortest interval between 2 consecutively conducted impulses. For example: in the atrium the FRP is the shortest A1-A2 interval that results from any S1-S2 stimulus. The FRP of the AVN is the shortest H1-H2 that results from any A1-A2 interval. *note you are measuring the output of the tissue, unlike ERP where you measure the interval between the inputs. Source: Josephson Text 2002

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4
Q

What is the “Effective Refractory Period” (ERP)?

A

The ERP of a tissue is the longest S1-S2 that fails to activate or propagate to that tissue. For example, the AERP is the longest S1-S2 coupling interval that fails to activate the atrium. The AVNERP is the longest A1-A2 that fails to propagate to the His bundle.

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5
Q

What is the ERP of the His-Purkinje System?

A

The ERP of the His-Purkinje System is the longest H1-H2 interval that fails to propagate to the V.

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6
Q

What interval should be measured when evaluating PVC’s placed into SVT once you have confirmed that you have advanced the A with a His refractory PVC?

A

You should measure the return cycle length of the tachycardia to confirm that you have reset the tachycardia. Otherwise, a pathway may be present but it may be a bystander.

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7
Q

How does stim to A time when entraining SVT from the RV help distinguish AVRT from AVNRT?

A

SA-VA > 85 ms indicates AVNRT

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8
Q

What is the difference between overdrive pacing and entrainment?

A

All entrainment is a form of overdrive pacing but not all overdrive pacing is entrainment. Entrainment requires fusion.

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9
Q

What are the three basic conditions that need to be present to even think about entrainment? Are these 3 things all that is necessary to demonstrate that entrainment has occurred? If not, what else?

A
  1. stable tachycardia c.l.
  2. able to pace and capture at a rate just faster than the tachycardia
  3. Same tachycardia resumes

To demonstrate fusion, you need to have constant fusion and progressive fusion.

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10
Q

In Knight’s 2000 JACC paper, 4 baseline (i.e. not in tachycardia) observations were recorded to help distinguish PSVT mechanism (atach vs ORT vs. AVNRT). What were they?

A
  1. preexcitation

​2. VA block c.l. > 600 ms

  1. Dual AVN physiology
  2. response to paraHisian pacing
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11
Q

How does the atrial activation pattern during ventricular overdrive pacing (or entrainment) of PSVT) help clarify the mechanism?

A

Alteration of the atrial activation pattern would suggest an atrial tachycardia or a bystander AP. If you are entraining an AVRT or an AVNRT form of SVT the atrial activation sequence during pacing should look the same.

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12
Q

Burst-pacing of the right ventricle for three to six beats is performed during tachycardia at cycle length of 250 ms. What happens and what does it mean?

A

There is termination of the tachycardia without impacting the atrial signal indicating that this is not an atrial tach.

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13
Q

What is the ventriculoatrial index?

A

VA interval at the apex - VA interval at the base. Martinez-Alday Circ 1994.

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14
Q

A positive ventriculoatrial index is indicative of:

A. AP retro conduction

B. AVN retro conduction

A

Answer: A.

The VA index is the VA timing at the Apex - VA timing at the base. A positive number indicates a shorter conduction time at the base c/w an AP.

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15
Q

A stim-to-proxCS time < 60 ms during paraHisian pacing is indicative of what?

A

simultaneous His and atrial capture.

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16
Q

This response to PHP suggests what type of retrograde conduction?

A

AVN/AVN using SP

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17
Q

This response to PHP suggests what type of retrograde conduction?

A

AVN/AVN via FP

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18
Q

This response to PHP suggests what type of retrograde conduction?

A

AP/AP retrograde conduction. Notice the S-H timing changes but the S-A timing does not, indicating that retro conduction is independent of the His timing.

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19
Q

Why is this not an example of PHP showing a nodal response?

A

Notice that the His to A time varies and retrograde conduction is eccentric and doesn’t change. This pattern is caused by conduction delay to a left-sided AP when the his purkinje system is not activated.

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20
Q

What percentage of patient’s will fail to have retrograde VA block with adenosine

A

According to a study by Souza JCE 1998, 38% of patients will have fast pathway retrograde conduction that persists despite 12 mg of adenosine.

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21
Q

What type of SVT is this an dwhat 2 features on this electrogram make the dx?

A

Notice the short VA timing and termination of SVT at the AV node. This suggests AVNRT.

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22
Q

What interval is measured to determine if you have an AP ipsilateral to a BBB during SVT? How is the interval measured?

A

The VA timing with without BBB measured from surface V line to earliest atrial activation. Note the tachycardia CL may decrease, increase or stay the same. Also local VA is not the appropriate measure!

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23
Q

How can the degree of VA prolongation with BBB during SVT help localize pathway location?

A

Free wall pathways typically show >35 ms prolongation with ipsilateral BBB vs. septal pathways that usually have less than 25 ms prolongation.

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24
Q

What info about the AP is shown?

A

The VA time prolongs with LAFB and LBBB indicating a left-sided AP

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25
Q

Which of the following responses to a PVC placed into SVT could indicate merely AP bystander status as opposed to actual participation?

A. slowing of the tachycardia

B. termination of tachycardia (without conduction to a)

C. advancing atrial activation during His refractory period

A

C. Advancing atrial timing during His refractory does not prove participation. Pathway could be bystander. In contrast, slowing or terminating SVT due to a PVC that does not affect atrial timing is consistent with AP participating in circuit.

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26
Q

Which form of SVT is ruled out by this maneuver?

A

Termination of this SVT without penetration to the atrium effectively rules out an A-tach.

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27
Q

Name 2 ways that you can tell if a PVC was placed with the His was refractory?

A
  1. Timing of the PVC - the PVC was placed within 45 ms of the his bundle depolarization, it should be refractory
  2. Check the QRS morphology. If the QRS of the PVC is fused, that suggests part anterograde His conduction and part PVC
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28
Q

What is learned from this diagnostic maneuver?

A

This His-refractory PVCs delays the return of the next atrial beat. This effectively rules out A-tach and AVNRT and confirms an AP mediated SVT.

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29
Q

What is learned from this diagnostic maneuver?

A

Ventricular overdrive pacing results in a VAAV response c/w an atrial tachycardia.

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30
Q

Why are the findings of this diagnostic maneuver NOT consistent with an atrial tachycardia?

A

This tracing actually demonstrates a pseudo VAAV response. Notice the timing of the last atrial beat shows this is really a VAV response. Also notice there is no change to atrial activation pattern.

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31
Q

What is learned from this diagnostic maneuver?

A

This is another example of a pseudoVAAV response caused by a long His-V time. Notice the His precedes the atrial activation.

32
Q

What is learned from this diagnostic maneuver?

A
  1. terminates tachycardia with block to the A (rules out Atach)
  2. fusion during the first PVC demonstrating His refractory status (rules out AVNRT)
  3. This must be an AP.
33
Q

What is learned from this diagnostic maneuver?

A

This is an example of a VAV response. This rules out an atrial tachycardia.

34
Q

What is learned from this diagnostic maneuver?

A

This is an example of a VAV response. SV-VA = 5ms, PPI-TCL is < 115 ms and the His is entrained anterograde. This must be AVRT using an AP.

35
Q

How is the SA interval during ventricular overdrive pacing measured?

A

The stimulus-atrial (SA) interval is typically measured from the last RV pacing stimulus to the last entrained depolarization in the
high right atrium.

36
Q

How is the corrected PPI-TCL difference calculated and why?

A

Ventricular overdrive pacing can increase the AH interval during entrainment. This is added into the PPI-TCL if not corrected. To correct for this, subtract the baseline AH interval during tachycardia from the post-pacing AH interval.

37
Q

What is the corrected PPI-TCL?

A

The correcte PPI-TCL is calculated by substracting the AH difference between the PPI AH and the baseline AH in SVT from the PPI-TCL. In this case the corrected PPI-TCL interval is 440-300-(130 - 80) = 90 ms.

38
Q

What is learned from this diagnostic maneuver?

A

This His synchronous PVC delays atrial activation. This is diagnostic of AP mediated AVRT.

39
Q

The PPI-TCL can be a useful way to distinguish AVNRT from AVRT, but doesn’t always work. When is this maneuver less reliable?

A

In long RP tachycardias with VA/TCL is > or = 40%, this maneuver only correctly predicted the mechanism half the time. Bennett Circ EP 2011.

40
Q

What is learned from this diagnostic maneuver?

A

Notice that the first fused beat during ventricular overdrive pacing delays conduction back to the A. Fusion confirms His refractory and delaying the A suggests a decremental pathway.

41
Q

What is learned from this diagnostic maneuver?

A

Atrial overdrive pacing produces an AHA response c/w AVNRT.

42
Q

How and when does one use the N+1 method to determine if the entrainment site is “in circuit” or “bystander?”

A

The N+1 difference is used when you can not measure the PPI on the pacing catheter due to saturation. Is is measured by substracting the Eg(n+2)-QRS(n+3) from S-QRS(n+1). Soejima K JACC 2001.

43
Q

Use the N+1 Difference Method to determine if the ablator “in circuit”.

A

The S-A(n+1) - [Eg(n+1) - A(n+2)] = 380-320 = 60. This site is a bystander.

44
Q

Is the map catheter in an: A. Isthmus, B. Outer loop, C. Exit, D. Bystander

A

Answer: B (in circuit but fusion is present = outer loop)

45
Q

Is the map catheter in an: A. Isthmus, B. Outer loop, C. Exit, D. Bystander

A

Answer: A. Isthmus (concealled fusion, short PPI). Notice the electrogram being captured by pacing is not the large signal. Measure back from the QRS the same distance as the simululs to QRS measurement to see what you are actually capturing.

46
Q

When adjudicating the timing of a complex electrogram in CARTO how can you determine which component of the electrogram is near field?

A

Pace at the site and determine the component of the electrogram that is captured.

47
Q

By convention, how does one define un-excitable scar

A

failure to capture during unipolar
pacing at 10 mA, 2 ms pulse width, despite apparently good
electrode tissue contact, were believed to signify anatomic
barriers to conduction.

Delacretaz E JACC 2001

48
Q

In addition to PPI - TCL < 30 ms, what other feature of a successful ablation site may be present during entrainment?

A

See if the surface p-wave demonstrates concealed fusion. If present and PPI-TCL less than 30 ms - high chance of ablative success. (Delacretaz E JACC 2001)

49
Q

Name one method for testing for phrenic nerve presence in the vicinity of a targeted catheter ablation site?

A

phrenic nerve stimulation was absent during unipolar pacing

at 10 mA, 2 ms stimulus strength. Delacretaz E JACC 2001

50
Q

The c.l. of this atach is 250 ms. Using the De Ponti method calculate the forward and backward windows

A

Backward window: TCL - Pwave dur + Pwave-Ref (negative) = 254-124/2 + (-56) = 9

Forward duration: (254-9) x 0.9 = 220

51
Q

The stim to earliest A timing gets longer when HIS capture is lost. Why is this NOT an example of a retrograde FP nodal response?

A

Notice that the increase in SA timing on CS 5,6 does not equal the increase in SH time when His capture is lost. Note also that stim to V activation in CS catheter changes with loss of His capture (also lose capture of purkinjie fiber?)

52
Q

Name 5 dx features that help identify an LA vs. RA source for a macro-reentry circuit

A
  1. Distal to proximal activation in the CS
  2. Earliest activation in the RA < 30 ms pre-P wave
  3. Early activation along Bachman’s bundle, septum, or CS ostium with fusion of wavefronts on the lateral wall
  4. No entrainment with concealed fusion from RA (long PPI-TCL from multiple sites)
  5. PPI-TCL > 50 ms from high RA (Miyazaki H et al. Heart Rhythm 2006; 3:516-23)
  6. Unable to electroanatomically map > 90% of tachycardia cycle length from RA
    (often < 50%)
  7. Variable RA cycle length with fixed LA cycle length
53
Q

When atrial flutter terminates during ablation, what aspects of the termination should be reviewed?

A
  1. termination was not caused by a PAC
  2. based on intracardiac electrogram timing, look at where in the reentry circuit the tachycardia was interrupted.
54
Q

According to a study published in heart rhythm in June 2015 how can one use noninvasive program stimulation from a pacemaker or ICD to determine the sidedness of an atrial flutter?

A

This study demonstrated that an atrial lead in the right atrial appendage that demonstrated a PPI minus TCL of greater than 100 ms indicated a left atrial flutter.

55
Q

In which of the following is the interval described NOT a pseudointerval?

A

A. The H-A interval during AVNRT

B. The H-A interval in Antidromic AVRT

C. the H-V interval in Bundle branch reentry VT

D. The H-V interval in Antidromic AVRT utilizing an atriofascicular pathway that inserts above the RB

(Asirvatham Circ AE Aug 2015 “Wobble”)

56
Q

During an EP study a concealed AP is diagnosed. Corrected PPI-TCL is 68 ms. Is this most likely a left or right sided AP?

A

Left. In a study published in PACE 2015 (first author Boonyapisit, W), authors found that corrected PPI-TCL was shorter for right sided pathway that left. In general, except septal pathways left sided pathways were > 55 ms.

57
Q

When the mechanism of tachycardia is thought to be reentry, but a large portion of the cycle length has not been accounted for in the map, what should be considered?

A

Incomplete anatomic definition

Mapping in the wrong chamber

Anatomic variant in the chamber of interest

A missing chamber

Inappropriate delineation of scar

Wrong diagnosis

58
Q

Name 4 reasons while ablation of an apparent a focal arrhythmia at the “early spot” may not be effective

A
  1. Overlapping or adjacent chambers (you’ve found the earliest spot in the wrong chamber (aortic SOV not RVOT, supra-pulmonary valve not RVOT, etc)
  2. You’ve identified an exit spot not the source (e.g. purkinje fibers
  3. deep myocardial or epicardial origin
  4. Wrong mechnanism - not a focal tachycardia
59
Q

Which electrogram will likely NOT be associated with ablation success?

A

A. - notice this electrogram does not have negative concordance in the bipolar and unipolar electrograms. Sorgete A HR 2015

60
Q

In addition to negative concordance of the first 20 ms of the bipolar and unipolar signals, what other 4 measurements can help determine if a signal is worth ablating?

A
  1. ) UniOn - Bip: The interval between the onset of the UEGM (UniOn) and the first peak (positive or negative) of the BEGM (Bip).
  2. ) UniOn - UniS The interval between the onset and the rapid negative deflection of the UEGM.
  3. ) BEGM-QRS The interval between the first peak (positive or negative) of the bipolar recording and the onset of the extrasistolic QRS complex
  4. ) UEGM-QRS The interval between the onset of the unipolar recording and the onset of the extrasistolic QRS complex

Sorgente HR 2015.

61
Q

Name 5 ECG features that favor VT over aberrated SVT.

A
  • Absence of typical RBBB or LBBB morphology
  • Extreme axis deviation (“northwest axis”) — QRS is positive in aVR and negative in I + aVF.
  • Very broad complexes (>160ms)
  • AV dissociation (P and QRS complexes at different rates)
  • Capture beats — occur when the sinoatrial node transiently ‘captures’ the ventricles, in the midst of AV dissociation, to produce a QRS complex of normal duration.
  • Fusion beats — occur when a sinus and ventricular beat coincides to produce a hybrid complex.
  • Positive or negative concordance throughout the chest leads, i.e. leads V1-6 show entirely positive (R) or entirely negative (QS) complexes, with no RS complexes seen.
  • Brugada’s sign – The distance from the onset of the QRS complex to the nadir of the S-wave is > 100ms
  • Josephson’s sign – Notching near the nadir of the S-wave
  • RSR’ complexes with a taller left rabbit ear. This is the most specific finding in favour of VT. This is in contrast to RBBB, where the right rabbit ear is taller.
62
Q

Is this WCT more likely VT or SVT? What are the eponyms associated with these arrows?

A

A QRS onset to S-wave Nadir of > 100 ms (Brugada’s sign) nad notching in the S-wave (Josephson’s sign) are c/w VT

63
Q

List 8 characteristics of atriofasicular pathways.

A
  1. Preexcitation on the routine 12-lead ECG is absent to minimal.
  2. The preexcited pattern elicited by pacing or during preexcited tachycardia has left bundle branch block
    morphology and generally a leftward axis. This is not surprising, since the distal insertion site is at or near the
    right bundle branch terminus.
  3. Pacing from right atrial sites provides more
    marked preexcitation and a shorter stimulus-to-QRS
    interval than pacing from left atrial sites at comparable cycle lengths
  4. The pathway exhibits rate-dependent or “decremental”
    conduction with prolongation of the A-to-delta interval with atrial extrastimuli or incremental atrial pacing.
  5. Retrograde conduction over the pathway is usually (always?) absent.
  6. The most commonly observed clinical tachycardia is antidromic tachycardia proceeding antegradely over
    the atriofascicular pathway and retrogradely over the normal AV conduction system.
  7. Associated AV node reentry and other accessory
    AV pathways are observed relatively frequently.
  8. During intracardiac recording, earliest ventricular
    activation during preexcitation is recorded at the right
    ventricular apical catheter with activation at or before
    the onset of the QRS on the surface ECG.
64
Q

During entrainment mapping, a pacing site exhibits concealed entrainment, but the PPI-TCL does not equal the tachycardia cycle length and the S-QRS does not equal the E-QRS interval. What part of the VT circuit is being sampled?

A

This would be a bystander

65
Q

What is the “skipped P-wave” phenomenon?

A

When the P-R interval exceeds the P-P interval, the P-wave following the long PR interval is “skipped”, because the ventricle is still refractory

66
Q

In Ebstein’s anomaly, due to fractionation of the ventricular electrogram, it can be difficult to distinguish the atrial component from the ventricular portion. Name 2 maneuvers than can help correctly adjudicate the timing of the A & V electrograms.

A

In sinus rhythm, a PAC below the APERP can separate out A and V electrograms. During ORT, placing a PAC synchronous with the V on set can pull the A out of the signal allowing one to determine which component was atrial. Cappato Circ 1996

67
Q

Describe a simple pacing maneuver to distinguish an AV (WPW) and NV fiber from a FV fiber.

A

Pace from the HIS bundle. If it is AV or “NV”, the LBBB QRS pattern should normalize. If it is FV and you are above the take of the fiber, the preexcitation pattern will not change.

68
Q

For scar-related reentry VT, when does the stimulus to QRS during pacing equal the EGM to QRS interval?

A

According to a review article by Zeppenfeld 2008, the S-QRS = E-QRS when you are in the circuit where PPI=TCL (either inner loop-concealed or outer loop-fusion). If you are remote where PPI > TCL with fusion and / or in a bystander space (fusion but PPI>TCL) then S-QRS does not equal E-QRS

69
Q

What might you consider if the return PPI is shorter than the tachycardia cycle length?

A

Consider the possibility that you are measuring to a far-field signal that is not being directly captured by the entrainment pacing. They can often be recognized
during pacing when they remain visible
and separate from the stimulus artifact during entrainment. Zeppenfeld 2008

70
Q

By convention, what are the voltage range criteria above which is considered healthy myocardium and below which is considered scar?

A

>1.5 mV healthy, less than 0.5 mv scar

71
Q

Entrainment of a WCT from the RV
apex with a PPI-TCL of less than 30 ms is suggestive of what type of tachycardia? What other features help confirm the diagnosis

A

BBR-VT. LBBB morphology. Wobble in his to his timing preceeds V to V timing.

72
Q

What is the incremental pacing maneuver and how is it used to assess CTI block?

A

The incremental pacing maneuver is simly decremental pacing (between 600 down to 300 ms) from either CS Os or LLRA wall and measuring the conduction time between split potentials. An increase in the timing between double potentials of >20 ms is indicative of only having functional CTI block, not true CTI block. Valles E JCE 2016

73
Q

Name 3 typical indicators of CTI block.

A
  1. Descending sequential activation along the lateral wall and the CTI when pacing from the CSO
  2. Descending sequential activation along the septal wall and the CTI when pacing from the LLRA
  3. Isoelectric line time between the two CTI potentials >70 ms
74
Q

Using decremental pacing, does this image show functional or true CTI block?

A

Decremental pacing does not increase the timing between double potential. This is consistent with true CTI block.

75
Q

Using decremental pacing, does this image show functional or true CTI block?

A

Decremental pacing increasing the timing between double potential by more than 20 ms. This is consistent with functional block not true CTI block.

EP (13 decks)

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