Noninvasive recording of His bundle activity with an analog delay device in normal subjects and patients with atrioventricular block.

A simplified and clinically applicable method has been developed for real-time noninvasive recording of the electrical activity of the His bundle in the human heart. A surface electrocardiogram (ECG) was obtained from bipolar precordial leads. The electrical signal within the P-QRS segment of the ECG was amplified with a high gain amplifier and delayed with an analog delay device for QRS-triggered signal averaging. The analog delay device consisted of a bucket brigade device (BBD) with an electrical integrated circuit (IC). After filtering with a band width of 50-300 Hz, the delayed signal was processed by a microcomputer system and the signal-to-noise ratio of the signal was improved by the signal averaging technique. Surface His bundle electrocardiograms (SHE) were measured in normal subjects without conduction disorders and in patients with atrio-ventricular (A-V) block. In the same patients, each SHE was nonsimultaneously compared with an invasive His bundle electrogram (HBE) obtained by the intracardiac catheter technique. The results of this comparison confirmed that the noninvasive method of SHE recording has broad clinical applicability and high utility for the screening of patients with latent A-V block before intracardiac catheterization is performed.