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Presentation Start/End
Time:
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Thursday, May 15,
2008, 2:00 PM - 2:15 PM
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Author Block:
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Ganiyu O. Oshodi, MBChB, Ottorino Costantini, MD,
Guy Amit, MD and David S.
Rosenbaum, MD. MetroHealth Campus/Case Western Reserve
University, Cleveland, OH
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Introduction:
Microvolt T wave alternans (MTWA) measured with the
exercise based spectral method (SPECTRAL) has been shown to identify patients
at risk for sudden cardiac death (SCD). An alternative method of measuring T
wave alternans, the Holter-based
modified moving average (MMA) method, has been developed. Because the two
methods account for noise and artifact in very
different ways, we hypothesized that they are not comparable in measuring
MTWA. Methods: Normal volunteers and
patients with LVEF < 0.40 underwent both SPECTRAL and MMA MTWA test. The
SPECTRAL test was obtained with a standard exercise protocol. The digital electrocardiographic data obtained from leads 2 and V1
during the SPECTRAL test was then analyzed via the Holter
based MMA method. Three analysis groups were defined: Group 1) healthy
volunteers; Group 2) SPECTRAL - patients; and Group 3) SPECTRAL + patients. The
maximal MMA-TWA value in the absence of artifact was recorded for every
subject. Results: 64 participants (20 healthy volunteers and 44 patients)
were tested. Indeterminate SPECTRAL tests (2 healthy volunteers and 11
patients) were excluded from the analysis. All of the healthy volunteers
(group 1: n=18) had a negative SPECTRAL test. Of the patients, 22 had a
negative SPECTRAL test (group 2) and 11 had a positive SPECTRAL test (group
3). The mean MMA-TWA values were 17.6µV, 19.7µV and 20.1µV for groups 1, 2
and 3 respectively. There was no statistical difference between the mean
maximal MMA-TWA values of the 3 groups (p = 0.873). Conclusions: The SPECTRAL
and the MMA MTWA test results are not equivalent and correlate poorly with
each other. Furthermore, the MMA test did not distinguish healthy volunteers
from patients with a positive spectral test. Conclusions from studies using
the SPECTRAL test that have established the utility of MTWA in predicting SCD
should not be extrapolated to the MMA test.
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