Study of T-wave spectral variance during acute myocardial ischemia

Several studies have shown that beat-to-beat variability of ventricular repolarization morphology, which can be measured by T-wave spectral variance (TSV) index based on the 2D-FFT, is asociated with an increased risk for developing ventricular arrhythmias. In the present study we tested TSV index during percutaneous coronary intervention (PCI) procedure in the orthogonal X, Y and Z leads for both non-filtered T-waves (T_N) and filtered T-waves (T_F, which was obtained by reducing the ST-segment modification due to acute ischemia). Also, we analyzed the intraindividual and interindividual variations of TSV index, in order to determine reliable limits of significant repolarization variability due to an ischemic cardiac process. The study group consisted of 62 patients, in which two ECG control and one ECG recording during PCI-procedure were obtained. Results indicate that TSV index showed significant differences during PCI-procedure respect to control situation in all ECG leads for both T_N (p <; 10^-8) and T_F (p <; 0.05). Moreover, TSV index presented a high stability in each patient and a significant larger variability between patients. We conclude that TSV index offers a robust tool for evaluating beat-to-beat repolarization variability during acute ischemia.