Ms. Ulgen et al., Contribution of the peak exercise QT dispersion to the accuracy of an exercise test during the evaluation of coronary artery disease, ACT CARDIOL, 55(6), 2000, pp. 335-339
Objective - Regional defects in ventricle repolarization are extremely sens
itive to ischaemia which can be measured as QT dispersion (QTd). We investi
gated the role of QTd calculated at the time of peak exercise during treadm
ill studies.
Methods and results - Thirty-three women and eighty men, whose treadmill te
st results and coronary angiography studies had been examined, were divided
into four groups according to the test results: 1)subjects with a negative
treadmill test and without significant stenosis results in the angiography
, were considered normal (N; n = 35); 2) subjects with both a positive exer
cise test and a significant presence of stenotic coronary arteries, were co
nsidered true positive (TP; n = 52); 3) subjects with a positive exercise t
est, but without significant stenosis results in the angiography, were cons
idered false positive (FP; n = 14); 4) subjects with a negative treadmill s
tudy, despite significantly stenotic arteries, were considered false negati
ve (FN; n = 12), All subjects were evaluated on the basis of age, significa
nt ST-segment depression, peak heart rate, rest and peak exercise QT, and Q
pT (measured from the beginning of the QRS complex to the highest point of
the T wave) dispersion, and corrected (QTcd, QpTcd) values for heart rate.
The most significant differences were observed between the N and the TP gro
ups in terms of QTd and QTcd (p < 0.01), with a higher correlation (r = 0.4
8). A significant relationship was also observed in terms of QpT and QpTcd
values during peak exercise (p < 0.01). The sensitivity of the peak exercis
e QTcd and QTcd greater than or equal to 70 ms in determining coronary arte
ry disease was found to be 74%. In cases of QTcd greater than or equal to 7
0 ms, in addition to ST-segment depression, the test was found to be less s
ensitive, but more specific at 96%.
Conclusion - It suggests that when peak exercise QTd and QpTd values are ta
ken into account, with the exception of the ST-segment depression, the accu
racy of the exercise test will increase and false positive results will dec
rease.