Detection and characterization of late potentials using time-frequency analysis techniques

Survivors of myocardial infarction are known to be highly susceptible to further cardiac arrhythmias including ventricular tachycardia (VT), which may lead to sudden cardiac death. The occurrence of non-stationary, low-amplitude, high-frequency signals in and beyond the terminal QRS complex of surface ECG recordings has been shown to be a marker for VT. These signals are known as "late potentials" or LP. Specialized forms of two time-frequency (T/F) signal analysis methods were developed and used to study LP in human ECGs. The ECGs with LP were found to exhibit extended fractionation in the T/F plane characterized by a slow rate of decay of the T/F energy from its maximum value. This observation was quantified by analyzing the settling times in the T/F distributions. ECGs with LP were found to have settling times that were twice as long as those found in normal ECGs, on average. These LP detection methods have potential applications as clinical diagnostic tools.