A computer-implemented electrocardiographic data processor with time stamp correlation is provided. A monitoring circuit includes a persistent memory and power supply that powers an encoder that determines a differential voltage between a current discrete digital voltage value and a prior voltage value. The differential voltage is stored into the persistent memory in a digitized data stream representative of analog cardiac action potential signals. Digitally-encoded voltage values and time stamps are retrieved from the persistent memory. A post-processing application executes. A set of output voltages and voltage differences that each correspond to lower and upper bounds of voltage is stored. Each retrieved voltage value is compared to the voltage bounds and the voltage differences within which each retrieved voltage value falls is identified. The output voltages corresponding to the voltage differences is selected. A display depicts the output voltages as reproduced analog cardiac action potential signals and correlates the time stamps.