Predictive value of wavelet correlation functions of signal-averaged electrocardiogram in patients after anterior versus inferior myocardial infarction

Objectives. This study sought to evaluate the prognostic value of wavelet correlation functions of the signal-averaged electrocardiogram (ECG) for arrhythmic events in patients after myocardial infarction. Background. Wavelet transform of the signal-averaged ECG has been shown to be nonstationary analysis technique describing the time evolution of frequency spectr throughout the QRS complex. To quantify the wavelet transform, we introduced the new concept of the wavelet correlation function. Methods. The relation among wavelet correlation functions, ventricular late potentials and the site of infarction was investigated in 769 men <66 years old who survived the acute phase of myocardial infarction (351 [46%] anterior, 418 [54%] inferior infarctions). Signal-averaged ECG recordings were obtained 2 to 3 weeks after infarction. During 6 months of follow-up, 33 patients (4.3%) experienced malignant arrhythmic event. Wavelet correlation functions of the signal-averaged ECG were evaluated in time-frequency plane ranging from 25 ms before QRS onset to 25 ms after QRS offset in the frequency range between 40 and 100 Hz. Results. Patients with an anterior infarction had lower mean wavelet correlation coefficients (p < 0.001) and lower incidence of ventricular late potentials than patients with an inferior infarction (32.3% vs. 42.7%, p = 0.003). The combination of wavelet correlation functions and late potentials increased the total predictive accuracy from 52% to 72% for inferior and from 64% to 76% for anterior infarctions. Conclusions. Spectral changes in the signal-averaged QRS complex are more prominent in anterior than inferior infarctions. Combination of late potential analysis and wavelet correlation functions increases the prognostic value for serious arrhythmic events after myocardial infarction.