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      Pattern of crescendo TWA may disclose the underlying cardiac pathology

      , , ,   , , , ,
      Journal of Electrocardiology
      Elsevier BV

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          Electrical alternation of the T-wave: Clinical and experimental evidence of its relationship with the sympathetic nervous system and with the long Q-T syndrome

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            Dynamic tracking of cardiac vulnerability by complex demodulation of the T wave.

            A link is found between T wave alternans and vulnerability to ventricular fibrillation, and a new approach is provided for quantification of susceptibility to malignant arrhythmias. Complex demodulation reveals that alternation of the electrocardiogram is concentrated during the first half of the T wave, coinciding with the vulnerable period of the cardiac cycle. During myocardial ischemia and reperfusion, there are marked increases in the degree of T wave alternans that parallel the established time course of changes in vulnerability. The influence of the sympathetic nervous system in arrhythmogenesis is also accurately detected. Ultimately, complex demodulation of the electrocardiogram could provide a technique for identification and management of individuals at risk for sudden cardiac death.
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              Upsurge in T-wave alternans and nonalternating repolarization instability precedes spontaneous initiation of ventricular tachyarrhythmias in humans.

              Analysis of repolarization instability, manifested by T-wave alternans (TWA), has proved useful for arrhythmia risk assessment. However, temporal relations between TWA and the spontaneous initiation of ventricular tachyarrhythmias (VTA) in humans are unknown. We examined continuous dynamics of repolarization in Holter electrocardiograms with spontaneous sustained (>30 seconds) VTA. Ambulatory electrocardiograms from 42 patients (79% with ischemic heart disease; left ventricular ejection fraction, 37+/-15%) were digitized, and the lead with the highest magnitude of the T wave was selected for analysis. TWA was examined by the modified moving average and intrabeat average analyses. To examine non-TWA (longer-period) oscillations in the repolarization segment, spectral energy of oscillations of consecutive T-wave amplitudes was calculated with the use of the short-time Fourier transform. Heart rate variability was assessed with the Fourier transform as well. TWA increased before the onset of VTA and reached a peak value of 23.6+/-11.7 microV 10 minutes before the event (P=0.0007). Spectral power of the oscillations of consecutive T-wave amplitudes increased nonuniformly, with the greatest increase in the respiratory range (2.6 microV2; P=0.005). In the TWA range, the change was smaller but highly pronounced relative to the 60- to 120-minute level (65%; P=0.003). The low-frequency and high-frequency heart rate variability power declined before the arrhythmia (P=0.04 and P=0.06, respectively). The magnitude of repolarization instability, manifested by TWA and beat-to-beat oscillations of T-wave amplitudes at other frequencies, increased before the onset of VTA. Tracking of these dynamics can facilitate timely detection of high-risk periods and may be useful for initiation of preventive treatments.
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                Author and article information

                Journal
                Journal of Electrocardiology
                Journal of Electrocardiology
                Elsevier BV
                00220736
                September 2010
                September 2010
                : 43
                : 5
                : 449-451
                Article
                10.1016/j.jelectrocard.2010.02.014
                bd31cf19-89e5-440f-8cf5-79b0704e417a
                © 2010

                http://www.elsevier.com/tdm/userlicense/1.0/

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