Predictive Value of T-wave Alternans Recorded from Electrograms of Implantable Cardioverter-Defibrillator
Category:  33 Device Technology
Presentation Time: Wednesday, 5:45 p.m. - 7:00 p.m.
Offir Paz, MD, Xiaohong Zhou, MD, Tracey Gerez, RN, Jennifer Grannis, MS, Hsiang-Jer Tseng, MS, Athula Abeyratne, PhD, Eli S. Gang, MD and Charles Swerdlow, MD. Cedars Sinai Medical Center, Los Angeles, CA, Medtronic Inc, Minneapolis, MN
Presentation Number: P1-66
Keyword: T-wave alternans, Implantable cardioverter-defibrillator
Microvolt T-wave alternans (TWA) on the surface ECG increases acutely prior to VT/VF in animals, suggesting that TWA recorded from ICD electrograms (EGMs) may warn of VT/VF in ICD pts. We have shown TWA has greater amplitude on ICD EGMs than on the ECG. But it is not known if EGM TWA represents the same pathophysiological process as ECG TWA, which is a good long-term predictor of spontaneous VT/VF. This study investigated the predictive value of EGM and ECG TWA. Methods: In 25 pts with dual-chamber ICDs and intact AV conduction, we recorded TWA during trials of atrial and AV pacing. Each trial consisted of 3 min of pacing at each of 3 rates (80, 95, and 110 bpm) for a total of 9 min per trial. EGM TWA was measured off line by spectral analysis. EGM TWA was positive (+) if either pacing method produced sustained alternans ≥ 30 μV with K score (signal-to-noise ratio) ≥ 3. Simultaneously, ECG TWA was analyzed by a commercial system (CHS2000, Cambridge Heart, Inc). ECG TWA was positive if either pacing method produced sustained alternans ≥ 1.9 μV with K score ≥ 3. The endpoint was appropriate ICD therapy for VT/VF during follow-up ≥ 6 months. Results: TWA tests were positive in 10 pts (40%) by ECG and in 13 pts (52%) by EGM. ECG and EGM TWA results were concordant in 21 pts (84%). During median follow-up of 7 months (range 6 - 13 months), 7 pts had appropriate ICD therapy. Of these, 6 pts had positive TWA tests by both ECG and EGM, and 1 pt had negative (-) TWA tests by both ECG and EGM. The figure shows that both ECG TWA (p = .006) and EGM TWA (p = .035) predicted event-free survival rate from appropriate ICD therapies. Conclusion: In ICD pts, ECG and EGM TWA have a high degree of concordance and similar predictive value for spontaneous VT/VF. This suggests that they represent the same pathophysiological process. Further studies are needed to determine if EGM TWA can serve as an immediate warning for VT/VF in ICD pts.