Cosinor-Based Circadianity of T-Wave Alternans Activity as a Predictor of Sudden Cardiac Death in Heart Failure: a Post-Hoc Analysis of the GISSI-HF Holter Substudy

Many studies in the last decades associate the existence of T-wave alternans
$(TWA)$
in the
$ECG$
to the risk of suffering malignant ventricular arrhythmias and sudden cardiac death
$(SCD)$
. In this work, 24-hour Holter
$ECG$
recordings from 388 patients aged 65±10 years with heart failure were analyzed. Three Holter recordings were acquired for each patient, allowing to assess the evolution of
$TWA$
over 1-year period. We measured the index of average alternans
$(IAA)$
, representing the average
$TWA$
activity along the whole recording, using a multilead fully automated method based on periodic component analysis
$(\pi CA)$
combined with the Laplacian likelihood ratio method (LLRM). The
$IAA$
was also measured for in 1- hour intervals, allowing to observe the influence of circadian rhythms on
$TWA$
. A circadian pattern was found showing the highest
$IAA$
values between 11:00 and 15:00 hours. The cosinor method was applied to adjust a sinusoidal wave to the results, finding that the MESOR (medium value of the adjusted sinusoidal wave) presented significant predictive power of SCD (Hazard Ratio:3.33(1.38-8.06), p=0.008) in the study population.