A wavelet-based high-frequency analysis of fragmented QRS complexes in patients with myocardial infarction

Fragmented QRS (fQRS) is an important and noninvasive marker for evaluating myocardial scar in patients with coronary artery disease, which is defined as additional spikes within the QRS wave. It is not easy to detect the fQRS accurately because of a variety of fQRS morphologies. This study is to analyze the high-frequency (HF) potentials of fQRS complexes using a continuous wavelet transform-based method in patients with myocardial infarction (MI). The HF parameter is defined as the root-mean-square (RMS) value of wavelet coefficients at the central frequencies of 100Hz, 150Hz, 200Hz, or 250Hz further normalized by the RMS value of the entire QRS complex, which is defined as the HF ratio. There were 76 MI patients and 43 Normal subjects recruited in this study. All of the ECG recordings were obtained from the PTB Diagnostic ECG Database including the conventional 12-lead and Frank XYZ lead ECGs. A signal averaging technology was adopted to reduce the background noise. The fQRS complexes were defined by the presence of an additional R wave, or notching in the nadir of the S wave, notching of the R wave, or the presence of more than one R prime. All of the mean HF ratios of the fQRS complexes are significantly larger than those of the non-fQRS complexes (p<;0.001). The total accuracy of the HF ratio for detecting the fQRS complex is about 80% (specificity 84% and sensitivity 60%) in the 12-lead ECGs, and about 84% (specificity 88% and sensitivity 65%) in the Frank lead ECGs.