System comprised of a portable medical device and method for registering electrocardiographic (ECG) signals, extracting and representing the most significant parameters at different levels of detail using the color-coded scales which are understandable to a lay person and a medical professional. Low, intermediate and high-resolution scales are defined according to the corresponding software and hardware resources. A low-resolution Scale I represents a small number of primary elements such as intervals between the heart beats, duration of PQ, QRS, and QT-intervals, amplitudes of P-, Q-, R-, S-, and T-waves. This real-time analysis is implemented in a portable device that requires minimum computational resources. The set of primary elements and their search criteria are adjusted for each ECG using intermediate or high-resolution levels. At the intermediate-resolution Scale II, serial changes in each of the said elements are determined using a mathematical decomposition into series of orthogonal basis functions and their coefficients. This scale is implemented using a specialized processor or a computer organizer. At the high-resolution Scale II, combined serial changes in all elements of the ECG are determined to provide complete information about the dynamics of the signal. This scale is implemented using a powerful processor, a network of computers or the Internet. The system can be used for personal or group self-evaluation, emergency or routine ECG analysis, or continuous event, stress-test or bed-side monitoring.