Electrocardiographic measures can facilitate the identification of patients at risk
of death after acute coronary syndromes. This study evaluates a new risk metric, morphologic
variability (MV), which measures beat-to-beat variability in the shape of the entire
heart beat signal. This metric is analogous to heart rate variability (HRV) approaches,
which focus on beat-to-beat changes in the heart rate. MV was calculated using a dynamic
time-warping technique in 764 patients from the DISPERSE2 (TIMI 33) trial for whom
24-hour continuous electrocardiograph was recorded within 48 hours of non-ST-elevation
acute coronary syndrome. The patients were evaluated during a 90-day follow-up for
the end point of death. Patients with high MV showed an increased risk of death during
follow-up (hazard ratio 8.46; p <0.001). The relationship between high MV and death
could be observed even after adjusting for baseline clinical characteristics and HRV
measures (adjusted hazard ratio 6.91; p = 0.001). Moreover, the correlation between
MV and HRV was low (R ≤0.25). These findings were consistent among several subgroups,
including patients under the age of 65 and those with no history of diabetes or hyperlipidemia.
In conclusion, our results suggest that increased variation in the entire heart beat
morphology is associated with a considerably elevated risk of death and may provide
information complementary to the analysis of heart rate.
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Article Info
Publication History
Published online: November 21, 2008
Accepted:
September 12,
2008
Received in revised form:
September 12,
2008
Received:
July 28,
2008
Footnotes
This work was supported, in part, by Center for Integration of Medicine and Innovative Technology, Harvard-MIT Division of Health Sciences and Technology, and Industrial Technology Research Institute (Taiwan). The DISPERSE2 trial was supported by AstraZeneca.
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Copyright
© 2009 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
