A Microcomputer System for On‐Line Study of Atrioventricular Node Accommodation

An automated on-line programmable stimulator and interval measurement system was developed to study atrioventricular node (AVN) accommodation. This dedicated microcomputer system measures and stores the stimulus-to-His bundle (S-H) interval from His bundle electrogram (HBE) recordings. Interval measurements for each beat are accurate to within 500 microsecond. This user-controlled system has been used to stimulate at any rate up to 6.5 Hz and to measure intervals up to 125 ms in isolated perfused guinea pig hearts. A built-in timer-reset mechanism prevents failure of the system in the absence of a His potential (i.e., 2:1 AV block). It may be modified for use in clinical studies or other experimental systems and has the ability to measure other physiological intervals. The system provides the precision in pacing and accuracy in the measurement of AVN conduction time that is necessary for meaningful analysis of AVN accommodation and has the simplicity of design and use that is not available in previously described systems. Furthermore, this computer system can be used not only in studies involving AV conduction, but also in any setting where programmed stimulation and interval measurement and recording need to be performed simultaneously.