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Presentation
Start/End Time:
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Sunday,
Mar 06, 2005, 10:00 AM -11:00 AM
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Author
Block:
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Theodore
Chow, Sinan
Gursoy, John R. Onufer, Karin M. Brinkman, Wenji Pu, Richard J. Cohen, The
MASTER Trial Investigators, The Lindner Center for Research and Education,
Cincinnati, OH
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Background: Microvolt T-Wave Alternans
(MTWA), a non-invasive test for assessing ventricular tachyarrhythmic risk,
has had reported rates of indeterminate test results typically in the 20% to
30% range. The effect of repeating indeterminate MTWA tests on the overall
indeterminacy rate is unknown.
Methods: The MASTER Trial is a 1500 patient prospective study
evaluating MTWA as a predictor of future spontaneous ventricular
tachyarrhythmic events in patients with prior myocardial infarction and LVEF
≤ 0.40. This trial uses the HeartwaveTM (Cambridge Heart, Inc.) for
measuring MTWA. The protocol requires that all tests classified by the
automated report classifier as indeterminate be repeated at the same testing
session as the initial test. Final classification of MTWA tests was
determined by an expert reader blinded to the clinical data. An interim
analysis of the effect of repeating indeterminate MTWA tests on the overall
indeterminacy rate was performed.
Results: Of 606 initial MTWA tests, 113 (18.6%) were classified as
indeterminate. The causes of indeterminacy were: non-sustained alternans
(32.7%), bad beats (32.7%), inadequate heart rate (23.0%), noise (10.6%), and
heart rate rise too rapid (0.9%). Repeat testing was performed on 65 of these
patients and resulted in a determinate result in 60%of the repeated tests
(MTWA positive in 35.4%, negative in 24.6%, indeterminate in 38.5%, and
technically inadequate in 1.5%). The initial cause for indeterminacy was not
significantly associated with whether repeating the test would yield a
determinate result. Final classifications for 606 patients included 280
(46.2%) as Positive, 240 (39.6%) as Negative, 59 (9.7%) as Indeterminate, and
27 (4.5%) as Technically Inadequate.
Conclusion: Repeating MTWA tests initially classified by the automatic
report classifier as indeterminate results in a determinate result in 60% of
repeated tests and reduces the overall indeterminacy rate to 9.7% (margin of
error 2.4%) which is substantially lower than previously reported.
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