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Presentation Time:
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11/15/2005 9:15:00 AM
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Title:
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"Indeterminate" T Wave Alternans Test Predicts High
Mortality Risk in Patients with Impaired Left Ventricular Function
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Keywords:
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Sudden death,Ventricular arrhythmia,Diagnostic
techniques,Electrocardiography,Exercise tests
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Author Block:
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Elizabeth S. Kaufman, Ottorino Costantini, MetroHealth Campus, Case
Western Reserve University, Cleveland, OH; Richard J. Cohen, Massachusetts
Institute of Technology, Cambridge, MA; Daniel M. Bloomfield, Richard C.
Steinman, Pearila B. Namerow, J. Thomas Bigger Jr, Columbia University, New
York, NY
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Disclosure Block:
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E.S. Kaufman, None; O. Costantini, None; R.J.
Cohen, Cambridge Heart, Modest,E. Ownership Interest (stock, stock
options, patent or other intellectual property); Medtronic, Cambridge
Heart, Modest,F. Consultant/Advisory Board; Board Member, Cambridge Heart,
Modest,G. Other; D.M. Bloomfield, None; R.C. Steinman,
None; P.B. Namerow, None; J.T. Bigger, None.
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Unlabeled/unapproved:
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There are no unlabeled/unapproved uses of drugs or products.
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Background: Microvolt level T
wave alternans (TWA) tests are used to stratify risk of sudden death in
patients with structural heart disease. TWA testing is potentially limited
by the large fraction of “indeterminate” tests, due to excessive
ventricular ectopy, unsustained TWA, or failure to achieve a HR of 105 BPM
for 1 minute (adverse patient factors), or to excessively rapid rise in HR
(HRRTR) or a noisy recording (testing technique factors). Hypothesis:
An “indeterminate” TWA test, when due to ectopy, unsustained TWA, or low
HR, has prognostic implications similar to a positive TWA test. Methods:
Adult patients with LVEF ≤ 0.40, in sinus rhythm, able to exercise on
a treadmill or bicycle, without unstable angina, class IV heart failure, or
prior sustained ventricular arrhythmia (SVA), underwent TWA testing. TWA
tests were classified by the Cambridge Heart computerized interpretation
algorithm. “Indeterminate” tests were reviewed independently by two readers
blinded to subsequent clinical events to determine the primary reason for
indeterminacy. The endpoint was all-cause mortality or documented non-fatal
SVA. Results: Subjects (N=549) were 56 ± 10 years old,
71% male; 49% had ischemic cardiomyopathy and 51% had non-ischemic cardiomyopathy.
There were 40 deaths and 11 non-fatal SVA. Comparing patients with an
“indeterminate” TWA test due to ventricular ectopy, unsustained TWA, or low
heart rate to those with a positive test, the hazard ratio was 1.3 (P =
0.10).
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TWA Test Result
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N (%)
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2-Yr Event Rate (%)
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Negative
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189 (34.4)
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2.5
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Positive
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162 (29.5)
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12.3
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Indeterminate
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198 (36.1)
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17.5
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Incomplete data
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14 (7.1)
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9.1
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Noise/HRRTR
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9 (4.6)
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0.0
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Unsustained TWA
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19 (9.6)
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21.8
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Heart rate <105 bpm
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94 (47.5)
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14.6
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Frequent ectopy
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62 (31.3)
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23.4
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Conclusion: In patients with
left ventricular dysfunction, an “indeterminate” TWA test due to
ventricular ectopy, unsustained TWA, or low heart rate predicts death or
SVA at least as well as a positive test. Conversely, a negative TWA result is
associated with a very low risk of death or SVA.
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