Extracted from European Heart Journal (2007) 28, 2303-2304
“In the present
study, TWA was determined
as an absolute value with a new time domainmodified
moving average method. The authors tested
multiple cut-off points and found that at 65 mV the
best
statistical values were obtained. However, since there
is
no gold standard, additional studies are needed in
other
specific populations to determine which amount of TWA
provides
the best diagnostic and prognostic information. The
sensitivity and positive predictive value of TWA were
fairly
low (,35 and ,15%), requiring additional diagnostic
tests
to establish cardiovascular risk. In the present
study, the
results and predictive value of exercise testing were
not
provided, thus the additional value of the TWA test
remains
unknown.
Another important issue concerns the mechanism of TWA
in this low risk, general population. TWA may be
observed
in patients with a history of MI as a strong predictor
for
cardiac death, even if LV function is preserved.3,4 In the
study by Nieminen et al., about 90% had a normal LVEF
on
echocardiography, although data were only obtained in
half of the patients. Up to 30% had a history of
coronary
heart disease including MI, and 40–50% had important
comorbidity
such as hypertension and diabetes mellitus, but
these did not surface as significant risk factors. One
wonders what the basis for the positive TWA test might
be
then in a patient without any apparent cardiac
abnormality.
There is no information on how these patients were
treated
during follow-up on the basis of either exercise test
or TWA
test, and whether this affected the natural outcome. Moreover,
how should one treat a person with a positive TWA test
in the absence of an identifiable substrate? The
mortality
end-points of the study were taken from public
records,
which may raise concern over definitions and
reliability.
How the TWA test related to specific causes of death
in
this population, such as acute coronary syndrome,
acute
heart failure, or ventricular arrhythmias, remains
unclear.”