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Presentation Start/End Time:
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Monday, Mar 31, 2008, 10:00 AM -11:00 AM
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Author Block:
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Theodore Chow, Dean J. Kereiakes,
John Onufer, Alan Woelfel, Sinan Gursoy, Brett J. Peterson, Mark L. Brown,
Wenji Pu, David G. Benditt, on behalf of the MASTER Investigators, Lindner
Center at The Christ Hospital, Cincinnati, OH
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Background: Microvolt T-wave alternans (MTWA) has
been proposed as a risk stratifier for life threatening ventricular
tachyarrhythmic events (LTVTE), particularly in patients with left
ventricular ejection fraction (LVEF) ≤ 30%. However, relatively little
data exist on the prognostic ability of MTWA in patients with moderate
ischemic left ventricular dysfunction (ILVD) (i.e. LVEF 31-40%).
Methods: MASTER II is a prospective registry conducted at 50 US
centers studying primarily community-based post-infarction patients with LVEF
31-40%. Baseline MTWA tests were classified according to standard criteria by
a blinded expert reader, with repeat testing of indeterminate tests.
According to the study protocol, only patients with a positive or negative
MTWA test were included in analysis. Patient treatment, including ICD implant
and programming, was left to physician discretion. Clinical and ICD events
were classified by a physician committee blinded to patient characteristics.
The primary outcome was LTVTE, defined as sustained spontaneous VT/VF, sudden
cardiac death, or appropriate ICD discharge. Cox proportional hazards
analyses were stratified according to whether or not an ICD was implanted.
Results: After exclusion of 45 patients testing indeterminate for
MTWA, analyses were conducted on 303 patients (85% males, mean age=64 ± 10,
mean LVEF= 36% ± 3%) who were followed for 2.2 ± 0.7 years. The final
distribution of MTWA test results was “positive” in 132 (44%), and “negative”
in 171 (56%). ICDs were implanted in 48% of patients. During follow-up LTVTEs
occurred in 7 MTWA positive and 4 MTWA negative patients with actuarial event
rates being 2.3%/yr and 1.0%/yr, respectively (p=0.25). A positive MTWA test
was not associated with increased LTVTE (stratified HR=1.22; 95% CI:
0.34-4.39, p=0.76), including after multivariate adjustment (stratified
HR=1.20; 95% CI: 0.33-4.31, p=0.79). However, the ability to detect a
significant difference may have been affected by the low event rate.
Conclusions: MTWA test result does not significantly discriminate risk
of LTVTE in patients with ILVD and LVEF 31-40%. However the incidence of
LTVTE among these patients in contemporary community practice is low.
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