Defibillator Electrogram T Wave Alternans as a Predictor of Spontaneous Ventricular Tachyarrhythmias in Defibrillator Recipients

Abstract

wave alternans (TWA), which is characterized by changes in the contour, amplitude or polarity of the T wave with regular rhythmicity, represents a temporal dispersion of repolarization. 1 Previous studies show that TWA is a marker of electrical instability in humans and is associated with life-threatening ventricular tachyarrhythmias (VTs). 2 TWA is known to be associated with various conditions, such as long QT syndrome, 3 Prinzmetal angina, 4 acute ischemia, 5 marked electrolyte abnormalities, 6 and hypertrophic cardiomyopathy. 7 The duration from the peak of the T wave to the end of the T wave (Tpte) is associated with transmural dispersion of repolarization, which is also related to the vulnerability to ventricular arrhythmias. 8 Tsai et al reported that TWA was a predictor of VT in a canine model of sudden cardiac death using intracardiac electrograms obtained from an implantable cardioverter defibrillator (ICD). 9 However, no one has previously investigated whether TWA and Tpte immediately precede or follow spontaneous VT in the human ambulatory setting. We hypothesized that TWA and the Tpte interval measured from the stored electrograms of ICD recipients would become prominent immediately before the spontaneous onset of clinical VTs. The purpose of this study was to determine whether TWA and the Tpte interval were measurable in the electrograms from ICD recipients, and if they were closely related to clinical VT. MethodsThis study was approved by the Institutional Review Board of Korea University Anam Hospital, and informed consent was given by each patient. Patient EnrollmentWe included 74 patients (age 55.3±12.2 years, males 79.7%) who had implanted ICDs. All patients had the transvenous-type ICD, and 5 of them underwent cardiac resynchronization therapy with a defibrillator. The ICD profiles were as follows: VENTAK MINI (Guidant Inc, Indianapolis, IN, USA), PRISM2 (Guidant Inc), GEM 7227 (Medtronic Inc, Minneapolis, MN, USA), GEM DR 7271 (Medtronic Inc), and Profile MD (St Jude Inc, Saint Paul, MN, USA). At a mean follow-up duration of 32.2±18.6 months, 17 patients had experienced 161 appropriate ICD therapies, and 5 patients received 6 inappropriate ICD shocks. Four patients with appropriate ICD therapies experienced ICD storms (>20 episodes per day). 10 Classification of ICD ElectrogramsThe total number of acquired stored ICD electrograms with tachycardia events was 167 (161 appropriate therapies, 6 inappropriate therapies). Taken together with 205 episodes of ICD shocks recorded during the measurement of (Received March 26, 2008; revised manuscript received August 22, 2008; accepted August 26, 2008; released online November 27, 2008 Defibillator Electrogram T Wave Alternans as a Predictor of Spontaneous Ventricular Tachyarrhythmias in Defibrillator RecipientsJin Won Kim, MD, PhD; Hui-Nam Pak, MD, PhD; Jae Hyung Park, BSc; Gi-Byoung Nam, MD, PhD*; Sook Kyoung Kim, MSc; Hyun Soo Lee, MPH;Jin Kun Jang, MD; Jong Il Choi, MD; Young-Hoon Kim, MD, PhDBackground Although T wave alternans (TWA) and the T ...

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T-Wave Alternans and Left Ventricular Wall Thickness in Predicting Arrhythmic Risk in Patients With Hypertrophic Cardiomyopathy

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