showing large interlead disparity in T-wave
morphology (increased repolarization heterogeneity). Such
hypothesis about the predominant role of the repolarization
morphology in predicting an individual predisposition to
ventricular arrythmias should be challenged by studying
torsadogenic drugs with small QT prolongation effect.
A prior work investigated the robustness of the T-loop
indices to slight shifts of QT interval definition; the authors
suggested that such transformation was robust to such
In our study, we lack such investigation; and the
reproducibility and robustness of our repol arization indices
should be demon strated in future works. Second, we opted to
use a pooled technique to correct our parameters for heart
rate. Such stra tegy generates an opportunity for a biased
estimation of the drug effect on the repolarization indices.
Indeed, we used the baseline data to estimate these
relationships, although we have shown that sotalol modifies
However, as of today, the authors do not
believe there is a more appropriate alternative to such
method when using 10-second ECG tracings.
The study presents a description of the effect of sotalol on
the T wave and the T loop and the effect of the changes in
plasma concentration of the drug on various repolarization
quantifiers. The study suggests that the peak plasma
concentration is synchronized with its peak effect on QT
interval but not with its peak effect on ventricular h etero-
geneity. These observations require confirmation in a larger
set of data; but today, they clearly reveal that drug-induced
QT prolongation represents only one aspect of the effect of
sotalol to the repol arization intervals from surface ECGs.
These observations might help design the next generation of
ECG markers for the e valuation of drug cardiotoxicity.
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