Multivariate discriminant analysis of ECG-based indexes to identify the occluded artery in patients undergoing PTCA

The spatial properties of ischemic changes induced by prolonged percutaneous transluminal coronary angioplasty (PTCA) have been studied. We have also analyzed how they are related to different indexes measured on the ECG (ST level, T-wave amplitude and position, QT interval and QRS duration) or derived from it [integrated measures based on the Karhunen-Loe`ve (KL) transform and applied to different ECG intervals]. There were no differences in the most sensitive leads to ischemic changes among the three coronary artery groups [the left anterior descending artery (LAD), right coronary artery (RCA) and left circumflex artery (CIR)] in which the angioplasty was done. The variations during the occlusion period of the different indexes were used in a multivariate discriminant analysis to determine which indexes showed the best discrimination of the three occlusion sites. Occlusions in the CIR were the most difficult to classify. With three local indexes (ST level measured in lead V3, T amplitude in lead I and ST level in lead III), it was possible to correctly classify 76% of patients by the occlusion site, and with three KL-derived indexes (α₀ ^STT in I, α₀^QRS in V3 and α ₀^QRS in I), 83% correct classifications were obtained. Using six indexes for local and KL-derived indexes, the correct classification rate was increased to 85% and 90% of patients, respectively. The use of different ECG measurements (from different intervals) on quasi-orthogonal leads has permitted the identification of the occluded artery in patients undergoing PTCA and may be extended for more general uses