Post-exercise assessment of cardiac repolarization alternans in patients with coronary artery disease using the modified moving average method.
OBJECTIVE
We sought to evaluate the utility of T-wave alternans (TWA) assessment in the immediate post-exercise period to identify and validate cutpoints for the modified moving average (MMA) assessment method.


BACKGROUND
The presence of TWA is associated with an increased risk of cardiovascular death (CVD). The immediate post-exercise period, where increased physiologic stress and minimal surface artifact coexist, appears ideal to implement the MMA method.


METHODS
A test (n = 322) and validation cohort (n = 681) provided 1,003 patients with coronary artery disease (CAD). We assessed TWA immediately after exercise. The outcomes, CVD and mortality, were adjudicated independent of the TWA results.


RESULTS
During 48 months of follow-up 85 deaths, 54 categorized as CVD (64%), were observed. A linear relationship between the magnitude of TWA and the risk of CVD was identified. As a continuous measure TWA voltage was equivalent to ejection fraction in predicting the risk of CVD. To facilitate clinical application, a sensitive, modest predictive accuracy (20 microV) and a specific, greater predictive accuracy MMA cutpoint (60 microV) were identified and validated. Each cutpoint was associated with a 2.5-fold greater risk of CVD, independent of other important variables, including ejection fraction.


CONCLUSIONS
Post-exercise assessment of TWA using the MMA method is a strong, independent predictor of risk in patients with CAD. The 20-microV cutpoint (87% sensitivity) appears to be most suitable in higher-risk patients, whereas the 60-microV cutpoint (95% specificity) appears more appropriate when TWA is used as a single screening test in those at lower risk. (Assessment of Noninvasive Methods to Identify Patients at Risk of Serious Arrhythmias After a Heart Attack; NCT00399503).
Slawnych
Michael P
MP
Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada.
Nieminen
Tuomo
T
Kähönen
Mika
M
Kavanagh
Katherine M
KM
Lehtimäki
Terho
T
Ramadan
Darlene
D
Viik
Jari
J
Aggarwal
Sandeep G
SG
Lehtinen
Rami
R
Ellis
Linda
L
Nikus
Kjell
K
Exner
Derek V
DV