Method and apparatus for determining a heart period from an ecg waveform using image representation of ecg

A system for estimating a heart period using at least one of a plurality of electrocardiogram recordings, comprising:

• a conversion machine for converting an at least one electrocardiogram recording into a corresponding electronic electrocardiogram image;
• a derivation machine for:
• deriving an electrocardiogram waveform from the corresponding electronic electrocardiogram image, by extracting an upper envelope and a lower envelope of the derived electrocardiogram waveform from the electronic electrocardiogram image using a curve tracing algorithm;
• determining an electrocardiogram signal peak from increased thickness at the electrocardiogram signal peak due to pixel dithering;
• and
• determining the difference between the upper envelope and the lower envelope at the electrocardiogram signal peak and at an electrocardiogram low point, which are a local maximum and a local minimum of the derived electrocardiogram waveform from the corresponding electronic electrocardiogram image;
• and
• an estimation machine for:
• computing a first order derivative of the derived electrocardiogram waveform for amplifying high frequencies of the derived electrocardiogram waveform;
• determining a peak of the derived electrocardiogram waveform by taking a product of a filtered electrocardiogram signal from the corresponding electronic electrocardiogram image in which a wandering baseline has been removed, a difference between the upper envelope and the lower envelope of the derived electrocardiogram waveform in the corresponding electronic electrocardiogram image and the first order derivative of the derived electrocardiogram waveform;
• and
• estimating the heart period as an average of intervals between a plurality of detected peaks from the at least one simultaneously selected region from each of the plurality of electronic electrocardiogram images and from the derived electrocardiogram waveform.

A processor implemented computer program product for estimating a heart period using at least one of a plurality of electrocardiogram recordings, comprising:

• computer program code performing on a computer processor in an electrocardiogram machine measuring electrical activity of a heart for:
• obtaining at least one of a plurality of electrocardiogram recordings generated from at least one of a plurality of electrocardiogram sources;
• converting at least one electrocardiogram recording into a corresponding electronic electrocardiogram image;
• removing noise from the corresponding electronic electrocardiogram image;
• deriving an electrocardiogram waveform from the corresponding electronic electrocardiogram image, by extracting an upper envelope and a lower envelope of the derived electrocardiogram waveform from the electronic electrocardiogram image using a curve tracing algorithm, the algorithm for extracting the upper envelope and lower envelope comprising:
• tracing upper and lower edges of a curve of the electrocardiogram waveform from the corresponding electronic electrocardiogram image;
• defining two search ranges centered around the upper and lower edges of the curve of the electrocardiogram waveform;
• using a morphological open algorithm to fill in holes inside the curve of the electrocardiogram waveform;
• using a morphological close algorithm to eliminate noise pixels near the curve of the electrocardiogram waveform;
• closing small gaps by closing the derived electrocardiogram waveform between inserted seed points along an expected location of the electrocardiogram waveform;
• and
• closing large gaps by inserting a segment tangent to the curve of the electrocardiogram waveform;
• and
• determining an electrocardiogram signal peak from increased thickness at the electrocardiogram signal peak due to pixel dithering;
• determining a difference between the upper envelope and the lower envelope at the electrocardiogram signal peak and at an electrocardiogram low point which are a local maximum and a local minimum of the derived electrocardiogram waveform from the corresponding electronic electrocardiogram image;
• estimating the heart period, by
• computing a first order derivative of the derived electrocardiogram waveform for amplifying high frequencies of the derived electrocardiogram waveform;
• determining a peak of the derived electrocardiogram waveform by taking a product of a filtered electrocardiogram signal from the corresponding electronic electrocardiogram image with a wandering baseline removed, the difference between the upper envelope and the lower envelope of the derived electrocardiogram waveform in the corresponding electronic electrocardiogram image, and the first order derivative of the derived electrocardiogram waveform;
• and
• estimating the heart period, as an average of intervals between a plurality of detected peaks from the derived electrocardiogram waveform;
• and
• outputting the estimated heart period on a user interface display.