1. TWA Testing in the EP Lab u To guide performance of EP study u To guide interpretation of EP study u To provide independent information along with the EP study

2. TWA Testing in the EP Lab u To guide performance of EP study u “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

3. Bayesian Probabilities u 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?

4. TWA Testing in the EP Lab u To guide performance of EP study u To guide interpretation of EP study –Rapid monomorphic VT –Polymorphic VT/VF

5. Rapid Monomorphic VT u “Ventricular flutter” u 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”) u 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

6. Ventricular Fibrillation u Accepted as positive endpoint in MADIT/MUSTT if induced with single/double VPDs u Known to have low specificity with triple VPDs u 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

7. AL u 61 year old F u Ischemic cardiomyopathy (LVEF: 15%) –Severe triple vessel disease and 4+ MR –Awaiting transplant (Class III CHF) u Telemetry: 5 bt NSVT

8. AL TWA Results

9. AL EPS Results u Long runs of self-terminating monomorphic VT (nonsustained) u VF with triple VPDs from RVOT u ICD implanted

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

11. JH TWA Results

12. JH EPS Results u Rapid sustained monomorphic VT (CL: 213 msec) induced with triple VPDs from the RVOT u ICD implanted

13. TWA Testing in the EP Lab u To guide performance of EP study u To guide interpretation of EP study u To provide independent information along with the EP study –Discordant results: »(-) TWA / (+) EPS »(+) TWA/ (-) EPS

14. Is EPS the Gold Standard? u MUSTT: (+) EPS 2yr Cardiac Arrest/Arrhythmic Death = 18% 18% u 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

15. Risk-Stratification: TWA/EPS u 215 pts undergoing EPS/TWA for known/suspected arrhythmias –60% syncope/presyncope –27% prior sustained ventricular arrhythmia –6% NSVT u 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

16. NSVT Pts: TWA vs. EPS u Prior studies have looked at heterogeneous populations (e.g. including pts with prior sustained arrhythmias) u We recently evaluated a homogenous population of 54 consecutive pts referred for EPS due to NSVT in the setting of CAD and LVEF  40%. u All pts underwent EPS with TWA testing Cohen et al, ACC, 2001

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

18. Event Rates of EPS and TWA SinglyIn 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).

19. WK u 82 year old M u Nonischemic cardiomyopathy u Class III CHF u LBBB u 4 beats NSVT

20. WK TWA Results

21. WK EPS Results u HV interval (79 msec, nl < 55) u VF with triple VPDs from RVOT u ICD with Biventricular pacing capability implanted

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

23. Conclusions u TWA testing routine part of “VT study” u Guide stimulation protocol u Help interpret ambiguous results u Identify high-risk patients despite negative EP study