Analysis of QRS shape variability and short-term heart rate variability of CAD patients

Beat-to-beat variability of the QRS shape and short-term heart rate of CAD patients were analyzed using high-resolution ECG and MCG record filtered by means of the Morlet wavelet transform. The shape variability was quantified by mean-to-standard deviation ratios of the envelope and the instantaneous frequency of band-pass signals located within the frequency range from 12 to 26 Hz. The heart rate variability was determined as the heart frequency deviation measured for a narrow-band envelope around 16 Hz. A simulation experiment showed that the beat-to-beat variability of the QRS signal can be detected down to a small level in the order of the background noise. A combined parameter weighting QRS variability and heart rate was used to distinguish CAD patients with VT from CAD patients without VT (t-test probability <0.001 for MCG and <0.02 for ECG).