Time-frequency analysis of high-frequency power profile within the QRS complex in patients with ventricular tachycardia using wavelet transform.

Background: Time-frequency analysis using continuous wavelet transform enables the detection of hidden frequency power within the QRS complex in electrocardiography. These frequency profiles may reflect myocardial damage and electrical dispersion. This study evaluated the frequency power profile in patients with a history of ventricular tachycardia (VT) using time-frequency analysis and assessed changes in the profile after catheter ablation.

Methods: Thirteen patients with a history of VT and 15 without who underwent implantable cardioverter-defibrillator implantation for secondary and primary prevention, respectively, were included. The time-frequency powers were calculated from QRS onset to the beginning of the T-wave in lead V5 on 3-min electrocardiography pre-implantation using continuous wavelet transform analysis. The frequency power of each scale band (40, 80, 150, 200, and 250 Hz) was evaluated using the mean of three continuous beats.

Results: The signal powers in high-frequency bands against that of 80 Hz were significantly higher in the VT group than in the non-VT group (250/80 Hz: 0.214 ± 0.060 vs. 0.146 ± 0.055, p = 0.004; 200/80 Hz: 0.282 ± 0.086 vs. 0.211 ± 0.082, p = 0.036; 150/80 Hz: 0.425 ± 0.118 vs. 0.341 ± 0.097, p = 0.049). Among 11 patients undergoing VT ablation in the secondary prevention group, the high-frequency component ratio significantly decreased post-ablation (250/80 Hz: 0.220 ± 0.062 to 0.183 ± 0.067, p = 0.015; 150/80 Hz: 0.424 ± 0.115 to 0.383 ± 0.108, p = 0.031). Peak signal powers of 250 Hz were detected within the QRS complex in all patients, with significant prolongation after ablation.

Conclusion: The distribution shift of the powers in the high-frequency bands was relevant in patients with VT. The time-frequency analysis was useful for stratifying ventricular arrhythmia risk.