High Amplitude T-wave Alternans Precedes Spontaneous Ventricular Tachycardia or Fibrillation in ICD Electrograms

Swerdlow, Charles D.; Zhou, Xin; Voroshilovsky, Olga; Abeyratne, Athula; Gillberg, Jeff

doi:10.1016/j.hrthm.2008.02.018

Cited by 45 publications

(47 citation statements)

References 17 publications

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“…Our findings 1 are consistent with those of Swerdlow et al who analyzed the TWA and T wave amplitudes on ICD electrograms preceding VT episodes, 6,7 Shusterman et al who reported that on the ECG TWA increases prior to VT/ VF but that the ECG T-wave amplitude does not, 8 and Narayan and Ahn who stated that TWA may arise even with low-amplitude T waves. 9 However, our study was not designed to address this issue and had the limitations of a small number of patients, local ICD electrograms, and multiple ICD models.…”

supporting

confidence: 92%

T Wave Alternans Detected in Defibrillator Electrograms: Reply

Pak

Kim

2009

Circ J

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We appreciate the interest expressed in our study 1 by Dr Madias. He had several questions regarding the relationship between the amplitude of the T wave and the T wave alternans (TWA) on implantable cardioverter defibrillator (ICD) electrograms. His first question was whether the amplitude of the T wave increased more prior to the onset of spontaneous ventricular tachycardia (VT)/fibrillation (VF) than immediately after induced VT or inappropriate ICD shocks. Second, he queried whether the amplitude of TWA in μV preceding spontaneous VT was larger in patients with ischemic rather than non-ischemic cardiomyopathy or in patients with idiopathic ventricular fibrillation. His third question was whether the magnitude of the TWA was larger before spontaneous VT than before induced VT in patients with ischemic cardiomyopathy. Fourth, he also posed a question about the amplitude of TWA immediately after appropriate ICD shocks in patients with spontaneous VT/ VF. Dr Madias reported that TWA may be T-wave-amplitude dependent, 2-4 and he has also posed similar questions about the relationship between T wave amplitude and TWA in other journals in the form of Letters to the Editor. 4,5 Theoretically, the T wave amplitude on surface 12-lead electrocardiography (ECG) is determined by the direction of the repolarization vector and the transmural repolarization gradient or apicobasal repolarization gradient. Therefore, discordant alternans of repolarization, which precede spontaneous VT/VF, are not dependent on the T wave amplitude.To address Dr Madias' questions, we performed additional analyses of T wave amplitudes and TWA on ICD electrograms. T wave amplitudes prior to spontaneous VT/ VF (VTclinic), immediately after ICD shock to induce VT (VTinduced), and immediately after inappropriate ICD shock (Shockinapp) were 272.7±127.9 μV, 342.2±250.7 μV, and 292.7±151.2 μV, respectively (P=NS). We did not find a correlation between T wave amplitude and TWA in these 3 groups (P=NS). We also compared T wave amplitude among disease groups, and at different times in the same patient (VTclinic vs VTinduced), but found no statistically significant differences. Therefore, our data suggest that changes in the T wave amplitude on ICD electrograms do not accurately predict either TWA or VT/VF.Our findings 1 are consistent with those of Swerdlow et al who analyzed the TWA and T wave amplitudes on ICD electrograms preceding VT episodes, 6,7 Shusterman et al who reported that on the ECG TWA increases prior to VT/ VF but that the ECG T-wave amplitude does not, 8 and Narayan and Ahn who stated that TWA may arise even with low-amplitude T waves. 9 However, our study was not designed to address this issue and had the limitations of a small number of patients, local ICD electrograms, and multiple ICD models. We also excluded ICD electrograms with a T wave amplitude <10 μV or an ambiguous T wave ending. Therefore, further investigation of Dr Maidas' hypothesis may be warranted. In summary, we suggest that although the TWA on an ICD electrogram is sign...

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confidence: 92%

T Wave Alternans Detected in Defibrillator Electrograms: Reply

Pak

Kim

2009

Circ J

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“…4,6,[11][12][13][14] To test this hypothesis, we developed and validated a method that measures TWA and nonalternans T-wave variability (TWA/V) from ventricular EGMs stored in ICDs before VT/VF. 15 Retrospective data indicate that EGM TWA/V is greater before spontaneous VT/VF than in limited baseline recordings 15 or after ICD shocks. 16 This prospective, multicenter study tested the hypothesis that high-amplitude EGM TWA/V precedes spontaneous VT/VF in ICD patients.…”

Section: Clinical Perspective On P 1060mentioning

confidence: 99%

“…We used a previously validated, simple averaging method 15 to measure EGM TWA/V on a beat-to-beat basis using custom software written in Matlab (release 7.0, version 14, Matlab Inc, Natick, MA). Briefly, after pairs with arrhythmic beats were removed, beat-to-beat alternans was calculated as the difference in T-wave amplitude of sequential beat pairs.…”

Section: Measurement Of Egm Twa/vmentioning

confidence: 99%

“…The number of pairs was selected as an approximate match to the number of preonset pairs (7) in our pilot study. 15 Thus, the durations of the individual analyzed control windows were comparable to those of preonset EGMs, and multiple TWA/V measurements were performed during each control recording. .…”

Section: Measurement Of Egm Twa/vmentioning

confidence: 99%

“…15 This simple averaging method takes advantage of 2 observations. First, the magnitude of TWA recorded from ICD shock EGMs is much greater than ECG TWA 11 and sufficient to permit beat-to-beat measurement without preprocessing the signal.…”

Section: Prior Studies Of Twamentioning

confidence: 99%

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Intracardiac Electrogram T-Wave Alternans/Variability Increases Before Spontaneous Ventricular Tachyarrhythmias in Implantable Cardioverter-Defibrillator Patients

Swerdlow

Chow

Das³

et al. 2011

Circulation

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Background-T-wave alternans (TWA) increases before ventricular tachycardia (VT) or fibrillation (VF), suggesting that it may warn of VT/VF in implantable cardioverter-defibrillator patients. Recently, we described a method for measuring alternans and nonalternans variability (TWA/V) from electrograms (EGMs) stored in implantable cardioverterdefibrillators before VT/VF. The goal of this prospective, multicenter study was to determine whether EGM TWA/V was greater before VT/VF than at baseline. Methods and Results-We enrolled 63 implantable cardioverter-defibrillator patients. TWA/V was computed from stored EGMs before spontaneous VT/VF and from sequential windows of 8 pairs of beats using 4 different control recordings: baseline rhythm, rapid pacing at 105 bpm, segments of ambulatory Holter EGMs matched to the time of VT/VF episodes, and EGMs before spontaneous supraventricular tachycardia. During follow-up, 28 patients had 166 episodes of VT/VF. TWA/V was greater before VT/VF (62.9Ϯ3.1 V; nϭ28) than during baseline rhythm (12.8Ϯ1.8 V; PϽ0.0001; nϭ62), during rapid pacing (14.5Ϯ2.0 V; PϽ0.0001; nϭ52), before supraventricular tachycardia (27.5Ϯ6.1 V; PϽ0.0001; nϭ9), or during time-matched ambulatory controls (12.3Ϯ3.5 V; PϽ0.0001; nϭ16). By logistic regression, the odds of VT/VF increased by a factor of 2.2 for each 10-V increment in TWA/V (PϽ0.0001). Conclusions-In implantable cardioverter-defibrillator patients, EGM TWA/V is greater before spontaneous VT/VF than in control recordings. Future implantable cardioverter-defibrillators that measure EGM TWA/V continuously may warn patients and initiate pacing therapies to prevent VT/VF.

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Brewer¹,

Kroll²

2009

TASER® Conducted Electrical Weapons: Physiology, Pathology, and Law

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High Amplitude T-wave Alternans Precedes Spontaneous Ventricular Tachycardia or Fibrillation in ICD Electrograms

Cited by 45 publications

References 17 publications

T Wave Alternans Detected in Defibrillator Electrograms: Reply

T Wave Alternans Detected in Defibrillator Electrograms: Reply

Intracardiac Electrogram T-Wave Alternans/Variability Increases Before Spontaneous Ventricular Tachyarrhythmias in Implantable Cardioverter-Defibrillator Patients

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