TWA Testing in the EP LabTWA 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

TWA Testing in the EP LabTWA 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

Bayesian ProbabilitiesBayesian Probabilities

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?

TWA Testing in the EP LabTWA Testing in the EP Lab

To guide performance of EP study To guide interpretation of EP study– Rapid monomorphic VT

– Polymorphic VT/VF

Rapid Monomorphic VTRapid Monomorphic VT “Ventricular flutter” Regarded by many as a nonspecific response to

stimulation protocol– MUSTT excluded induced VTs with cycle length <

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

Ventricular FibrillationVentricular 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

ALAL

61 year old F Ischemic cardiomyopathy (LVEF: 15%)– Severe triple vessel disease and 4+ MR

– Awaiting transplant (Class III CHF) Telemetry: 5 bt NSVT

AL TWA ResultsAL TWA Results

AL EPS ResultsAL EPS Results

Long runs of self-terminating monomorphic VT (nonsustained)

VF with triple VPDs from RVOT

ICD implanted

JHJH

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

JH TWA ResultsJH TWA Results

JH EPS ResultsJH EPS Results

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

ICD implanted

TWA Testing in the EP LabTWA 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

Is EPS the Gold Standard?Is EPS the Gold Standard?

MUSTT: (+) EPS 2yr Cardiac Arrest/Arrhythmic Death = 18%

18%

MUSTT: (-) EPS 2yr Cardiac Arrest/Arrhythmic Death = 12%

12%

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

1 out of 8 (-) EPS pts will have an event in 2 years

Buxton et al, NEJM 2000; 342 (26):1937

Risk-Stratification: TWA/EPSRisk-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 2000;36:2247

NSVT Pts: TWA vs. EPSNSVT 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

Results: TWA vs. EPSResults: 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

EPS (+) EPS (-) TotalTWA (+) 15 6 21TWA (-) 12 8 20TWA (indeterminate) 9 4 13Total 36 18 54

Event Rates of EPS and TWAEvent Rates of EPS and TWA

Singly In Combination

EPS+25% EPS+, TWA+39%

TWA+25% 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).

WKWK

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

WK TWA ResultsWK TWA Results

WK EPS ResultsWK EPS Results

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

ICD with Biventricular pacing capability implanted

Implant EconomicsImplant Economics

Review of ICDs by insurers (esp. Medicare) is strict!– Expect close scrutiny

of implants that do not adhere to ACC/AHA guidelines

ConclusionsConclusions

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

negative EP study