Ventricular late potentials in patients with and without inducible sustained ventricular tachycardia: a combined analysis in the time and frequency domain.

Time and frequency of signal-averaged electrocardiograms from 51 patients and 19 normal subjects were studied. A new filter device was designed to facilitate the analysis of the complete QRS complex, particularly the high-frequency components. All patients underwent electrical programmed stimulation (EPS) with up to three extra stimuli. In 29 patients, sustained ventricular tachycardia (VT) was inducible (group A), whereas in 22, sustained VT could not be elicited (group B). Between A and B, we compared several variables from the signal-averaged ECG as well as clinical data. The variables that differed between the two groups (P less than 0.01) were entered into a logistic regression model to determine which ones could most reliably predict the outcome of EPS. A combination of three variables (number of minima and maxima in the terminal QRS; third of four areas of equal length, divided by the total area below the QRS; maximum of the frequency spectre in the terminal QRS) could predict the inducibility of sustained VT with 82.8% sensitivity and 86.4% specificity.