TWA Testing in the EP Lab

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TWA Testing in the EP Lab

• To guide performance of EP study
• To guide interpretation of EP study
• To provide independent information along with the
  EP study

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TWA Testing in the EP Lab

• To guide performance of EP study
• Universal stimulation protocol
• NASPE Task Force, 1985
• 90 sensitivity in pts with a history of
  sustained VT and prior MI
• 1, 2, and 3 VPDs with at least two drive train
  cycle lengths at each of two ventricular sites
• Additional pacing sites, including left
  ventricular sites, should be considered if
  clinically appropriate and associated with an
  acceptable risk/benefit ratio
• Pharmacologic stimulation (e.g.
  isoproterenol/dobutamine) not standardized

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Bayesian Probabilities
Sensitivity
PPV
likelihood
Pre-test
NPV
Specificity

• Use pre-test TWA results to guide aggressiveness
  of stimulation protocol, to optimize predictive
  value of EPS
• Third site?
• Iso/Dobutamine at 1 or 2 sites?

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TWA Testing in the EP Lab

• To guide performance of EP study
• To guide interpretation of EP study
• Rapid monomorphic VT
• Polymorphic VT/VF

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Rapid Monomorphic VT

• Ventricular flutter
• Regarded by many as a nonspecific response to
  stimulation protocol
• MUSTT excluded induced VTs with cycle length lt
  220 msec (if no isoelectric interval between
  consecutive QRS complexes)
• However, in analyzing pts undergoing ICD implant
  for syncope and inducible VT, we found no
  difference in the subsequent event rate comparing
  pts with and without very rapid monomorphic VT

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Ventricular Fibrillation

• Accepted as positive endpoint in MADIT/MUSTT if
  induced with single/double VPDs
• Known to have low specificity with triple VPDs
• ACC/AHA ICD Implant Guidelines
• Syncope of undetermined origin with clinically
  relevant sustained VF
• Inducible VF in pts with nonsustained VT and
  coronary disease, prior MI, and LV dysfunction

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AL

• 61 year old F
• Ischemic cardiomyopathy (LVEF 15)
• Severe triple vessel disease and 4 MR
• Awaiting transplant (Class III CHF)
• Telemetry 5 bt NSVT

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AL TWA Results
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AL EPS Results

• Long runs of self-terminating monomorphic VT
  (nonsustained)
• VF with triple VPDs from RVOT

• ICD implanted

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JH

• 56 year old M
• Mild LV dysfunction following MI and PTCA of LAD
  (LVEF 40)
• 2 runs of NSVT (up to 10 beats) during a stress
  test
• Fixed apical and anterior defects

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JH TWA Results
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JH EPS Results

• Rapid sustained monomorphic VT (CL 213 msec)
  induced with triple VPDs from the RVOT

• ICD implanted

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TWA Testing in the EP Lab

• To guide performance of EP study
• To guide interpretation of EP study
• To provide independent information along with the
  EP study
• Discordant results
• (-) TWA / () EPS
• () TWA/ (-) EPS

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Is EPS the Gold Standard?
18
12

• MUSTT () EPS 2yr Cardiac Arrest/Arrhythmic
  Death 18

4 out of 5 () EPS pts will not have an event in
2 years

• MUSTT (-) EPS 2yr Cardiac Arrest/Arrhythmic
  Death 12

1 out of 8 (-) EPS pts will have an event in 2
years
Buxton et al, NEJM 2000 342 (26)1937
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Risk-Stratification TWA/EPS

• 215 pts undergoing EPS/TWA for known/suspected
  arrhythmias
• 60 syncope/presyncope
• 27 prior sustained ventricular arrhythmia
• 6 NSVT
• 400 Day Rate of VT or Death
• EPS () 25 EPS (-) 10
• TWA ()26 TWA (-) 3

Gold et al, J Am Coll Cardiol 2000362247
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NSVT Pts TWA vs. EPS

• Prior studies have looked at heterogeneous
  populations (e.g. including pts with prior
  sustained arrhythmias)
• We recently evaluated a homogenous population of
  54 consecutive pts referred for EPS due to NSVT
  in the setting of CAD and LVEF ? 40.
• All pts underwent EPS with TWA testing

Cohen et al, ACC, 2001
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Results TWA vs. EPS

• 36 pts (67) had () EPS
• 21 pts (39) had () TWA vs. 20 (37) (-) TWA and
  13 (24) indeterminate
• Excluding indeterminates, 18/41 discordant
  studies (44)
• Prospective f/u ongoing to determine risk in
  TWA(-)/EPS() and TWA()/EPS(-) pts

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Event Rates of EPS and TWA

• Singly In Combination
• EPS25 EPS, TWA 39
• TWA25 EPS-, TWA 15
• EPS- 5 EPS, TWA- 12
• TWA- 1.5 EPS-, TWA- 0

Gold MR, et al. (FDA-Cleared Labeling, Cambridge
Heart, Inc. K No. 983102).
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WK

• 82 year old M
• Nonischemic cardiomyopathy
• Class III CHF
• LBBB
• 4 beats NSVT

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WK TWA Results
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WK EPS Results

• HV interval (79 msec, nl lt 55)
• VF with triple VPDs from RVOT

• ICD with Biventricular pacing capability implanted

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Implant Economics

• Review of ICDs by insurers (esp. Medicare) is
  strict!
• Expect close scrutiny of implants that do not
  adhere to ACC/AHA guidelines

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Conclusions

• TWA testing routine part of VT study
• Guide stimulation protocol
• Help interpret ambiguous results
• Identify high-risk patients despite negative EP
  study