Intra-QRS analysis of high frequency signal components in patients with congenital heart disease

Patients with congenital heart disease were investigated after operation using the echocardiogram, signal-averaged ECG (SAECG) and Holter ECG. 32 patients, age 13.1 y (5-31 y) and 13 controls, 14.0 y (8-21 y), were compared. Together with Butterworth filtering a second high pass filter (FIR digital filter) was introduced to analyse high frequency components not only at the end of the QRS complex. FIR high pass filtering of the whole QRS showed a significant correlation between impaired left ventricular ejection fraction and more fractionated QRS in the SAECG (p<0.003). No correlation was found between dysrhythmias in the 24-hour Holter ECG and SAECG findings. High frequency intra-QRS signal components seem to be related to functional impairment in patients with congenital heart disease after operation.