Novel decision strategy for P-wave detection utilising nonlinearly synthesised ECG components and their enhanced pseudospectral resonances

Abstract

A novel, robust, patient adaptive and potentially on-line P-wave detection decision strategy is presented. It is particularly well-suited to the noisy ECG environment, and highly effective with abnormal atrial activations which can occur simultaneously with the QRS complex or the T-wave. Essentially, it is based on the exploitation of the unique structural properties of the raw and nonlinearly synthesised high-resolution pseudospectral multi-resonance signatures of the P-wave (or the entire PR interval including the P-wave), QRS complex, and the combined S-T segment and the T-wave. Clinical trials involving 59 healthy volunteers, equivalent to 1600 hours of ECG recordings, sampled at 500 Hz, have confined that most of the atrium and ventricle depolarisation-wave spectral energies (approximately 90%) are confined to two overlapping clusters inscribed by the top of the principal pseudospectral peaks (PPPs) and centred at 12 and 15 Hz, respectively. The degree of overlapping varies from one person to another and can, to some extent, be reduced by using a temporal interleaving technique or sub-sampling. Normal sinus records obtained from the MIT/BIM database and sampled at a lower rate of 128 Hz have confirmed the above, thus facilitating an easy decision strategy for all the P-waves that bear relationships to the following QRS complexes. For the P-on-QRS and the P-on-T episodes, the linear and quadratic PPPs are used in the detection of independent P-waves, respectively. The results presented here include a representative of 59 cases of sinus rhythm and three cases of challenging arrhythmias. One observation of mechanical contraction of the atrium and using echocardiographic imaging coinciding with the P-wave is presented to demonstrate the clinical fall-outs resulting from detection of dependent as well as independent P-waves. In arrhythmias cases, the standard 12-lead or the 3-lead machines were used as appropriate. The multi-faceted detection routine employs temporal and frequency interleaving, the LMS-based cubic Volterra synthesiser in conjunction with Kaiser-filtered state-enhanced spectral MUSIC, and subsequent thresholding. An adaptive multi-level thresholding with first derivative calculations is only activated in suspected cases of several independent P-waves perturbing the QRS complex.