1. A method for estimating a heart period using at least one of a plurality of electrocardiogram recordings, comprising: obtaining the plurality of electrocardiogram recordings generated from a plurality of electrocardiogram sources, wherein the plurality of electrocardiogram sources include a paper form electrocardiogram source, a digital form electrocardiogram source, and an echocardiogram from an echocardiogram source; utilizing a computer processor to convert a plurality of the electrocardiogram recordings into a plurality of corresponding electronic electrocardiogram images, including removing a wandering baseline from the electrocardiogram recordings prior to conversion of the electrocardiogram recordings to the corresponding electrocardiogram images; deriving an electrocardiogram waveform from one of the corresponding electronic electrocardiogram images by extracting an upper envelope and a lower envelope of the electrocardiogram waveform from one of the corresponding electronic electrocardiogram images using a curve tracing algorithm; determining an electrocardiogram signal peak from increased thickness at the electrocardiogram signal peak due to pixel dithering; determining a difference between an upper envelope and a lower envelope at an electrocardiogram signal peak and at an electrocardiogram low point, which are a local maximum and a local minimum of one of the corresponding electronic electrocardiogram images; and estimating the heart period.