Real-time beat-to-beat measurement of conduction intervals during cardiac electrophysiological studies

On-line interval measurement during invasive cardiac electrophysiologic testing

A microprocessor-based timer has been developed for routine and research use in cardiac electrophysiologic studies. The cycle length (A-A) and the conduction times through the right atrium (A(HRA)-A(HIS], the AV node (A-H) and the His-Purkinje system (H-V) can be automatically measured beat-to-beat in real-time both during sinus rhythm and during atrial pacing. The design has been refined during three years of use in over 80 clinical studies. A comparison between manual and automatic measurements has been executed for randomly chosen portions of 10 studies. With the manual measurements as reference procedures the sensitivities of the automatic measurements of the A, H and V waves were 0.98, 0.88 and 0.92, respectively, while the specificities were 0.93, 0.92 and 0.93, respectively. For the true positive measurements the correlation coefficients of the intervals were r(A-A) = 0.9998, r(A-H) = 0.987 and r(H-V) = 0.988. The statistical analysis of the differences between manual and automatic readings for the intervals A-A, A-H and H-V yielded mean values of -1 ms, -0.8 ms and 0.6 ms and standard deviations of 3 ms, 4 ms and 4 ms which are smaller than the accuracy of the common manual measurements.

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.