A program to measure time intervals between R wave peaks in real-time mode

Assuming a sampling rate of electrocardiograms of 200/s, the time interval between two successive analog-to-digital conversions is 5 ms. We present a program which recognizes R wave peaks of electrocardiograms and measures R-R time intervals within this critical period. The program is written in assembly language and run on a PDP-12. The cycle time is 1.6 microseconds and most instructions require one to three cycles for execution in the computer used. Since the whole sequence of this program is executable in about 160 microseconds, electrocardiograms recorded on a data recorder can be analysed 31 times faster than recording speed. For application of this routine, we present a program for displaying an R-R interval histogram and a joint interval histogram.