Relation of principal components of ECG maps to loci of wall motion abnormality in old myocardial infarction

The purpose of this study was to examine the correlation between body surface potential distribution and the extent of abnormally contracting segments (ACS) of the left ventricle in patients with old myocardial infarction (MI). Body surface potential distribution was quantitatively analyzed using principal component analysis. The first six principal components were extracted from data set obtained from both 25 normal subjects and 100 patients. The z scores (principal component weights) were calculated in a time domain at every 4 or 8 ms in another 81 patients with previous MI. In anterior MI, the second z scores on T wave and the fourth z scores on QRS complex were significantly lower in the presence than in the absence of ACS at the lateral wall. In inferior MI, the first z scores on QRS complex, the second on T wave, and the third on both Q and T represented significant differences between the presence and the absence of ACS at the posterior wall. Minute differences in the extent of ACS were sensitively and noninvasively detected on z scores of principal components.