Method and apparatus for spectral analysis of electrocardiographic signals

A method for analyzing in the frequency domain a single cycle of an ECG signal, which single cycle may be an ensemble average of a plurality of cycles, said method comprising:

• a. locating within said ECG signal, a time interval of interest, typically the QRS region of said ECG signal;
• b. dividing said time interval of interest into a sequence of overlapping segments, or slices;
• c. multiplying each said slice by a windowing function to form a windowed slice;
• d. performing a discrete fast Fourier transform (FFT) on each said windowed slice, in which FFT the power spectral density (PSD) at a sequence of frequencies is calculated;
• e. producing a numerical matrix or table of PSD's in which discrete frequencies head each column in said table and discrete times head each row of said table, thereby resulting in a matrix of PSDs for a vertically-stacked array of time-slices, and,
• f. comparing said matrix of PSD s with corresponding matrices obtained from representative samples of normal and abnormal test subjects.

An apparatus for analyzing ECG signals to detect abnormalities of electrical conduction within the heart comprising:

• (a) means for selectably storing a waveform representative of the amplitude-versus-time variation of a single cycle of said ECG signal, or an ensemble average of said cycles;
• (b) means for locating within said waveform a time interval of interest;
• (c) means for dividing said time interval into a sequence of overlapping segments, or time slices;
• (d) means for performing a frequency analysis of each of said overlapping segments;
• (e) means for producing a numerical matrix table of the amplitude of each frequency component obtained by said frequency analysis means, said matrix table having in a first line of headings discrete frequency values, and in a second orthogonal line of headings, discrete time intervals corresponding to the beginning of each slice, and
• (f) means for comparing said table with corresponding tables obtained from normal and abnormal test subjects.