Wavelet analysis and time-frequency distributions of the body surface ECG before and after angioplasty

In a pilot study, electrocardiographic (ECG) recordings of patients with le ft and right coronary stenosis taken before and after angioplasty were anal yzed using the continuous wavelet transform. Time-frequency distributions w ere obtained for different leads in order to examine the dynamics of the QR S-spectrum and establish features specific of ischemia in the time frequenc y domain. We found relevant changes in the mid-frequency range, reflecting the ECG's response to percutaneous transluminal coronary angioplasty (PTCA) . The changes appeared in ECG leads close to ischemic zones of the myocardi um. Time frequency distributions of the ECG during the QRS may thus become another electrocardiographic indicator of ischemia, alternative to ST-level in standard ECG or body surface mapping. The paper demonstrates the abilit y of the continuous wavelet transform to detect short lasting events of low amplitude superimposed on large signal deflections. (C) 2000 Elsevier Scie nce Ireland Ltd. All rights reserved.