Cl. Hubleykozey et al., SPATIAL FEATURES IN BODY-SURFACE POTENTIAL MAPS CAN IDENTIFY PATIENTSWITH A HISTORY OF SUSTAINED VENTRICULAR-TACHYCARDIA, Circulation, 92(7), 1995, pp. 1825-1838
Background Regional disparities of ventricular primary-repolarization
properties contribute to an electrophysiological substrate for arrhyth
mias. Such disparities can be assessed from body-surface distributions
of ECG QRST areas. Our objective was to isolate and test those featur
es of QRST-area distributions that would be suitable for identifying p
atients at risk for life-threatening ventricular arrhythmias. Methods
and Results We recorded ECGs simultaneously from 120 leads during sinu
s rhythm for 204 patients taking no antiarrhythmic drugs: half had had
sustained ventricular tachycardia (VT); the other half, a myocardial
infarction but no history of VT. For each patient, we calculated the Q
RST area in each lead and, using Karhunen-Loeve (K-L) expansion, reduc
ed these data to 16 coefficients (each relating to one spatial feature
, an eigenvector, derived from the total set of 204 QRST-area maps). U
sing stepwise discriminant analysis, we selected feature subsets that
best discriminated between the two groups, and we estimated by a boots
trap procedure using 1000 trials how these subsets would perform on a
prospective patient population. The mean diagnostic performance of the
classifier for 1000 randomly selected training sets (n = 102 in each,
with both groups equally represented) increased monotonically with th
e number of features used for classification. The initial trend for th
e corresponding test sets (n = 102 in each) was the same but reversed
when the number of features exceeded eight. For an optimal set of eigh
t spatial features, the sensitivity and specificity of the classifier
for detecting patients with VT in 1000 test sets were (mean+/-SD) 90.3
+/-4.3% and 78.0+/-6.1%, and its positive and negative predictive accu
racies were 80.7+/-4.2% and 59.2+/-4.2%, respectively. Use of QRS dura
tion as a supplementary feature to eight K-L coefficients can, in the
test sets, increase specificity to 80.9+/-5.4% and positive predictive
accuracy to 82.8+/-3.9% compared with the results for the optimal num
ber of eight K-L features alone. Conclusions Multiple body-surface ECG
s contain valuable spatial features that can identify the presence of
an arrhythmogenic substrate in the myocardium of patients at risk for
ventricular arrhythmias. Our results compare very favorably with those
achieved by any other known test, invasive or noninvasive, for arrhyt
hmogenicity.