His Bundle Electrogram

RECENTLY, a simple technic for electrode catheter recording of consistent and stable His bundle activity was described, first in the dog" 2 and then in man.3 In the short time since the introduction of this technic there have been numerous reports utilizing His bundle recordings. These studies have confirmed many of the earlier ingenious deductions made by clinical electrocardiographers utilizing the surface electrocardiogram alone. The His bundle electrogram, in conjunction with the surface electrocardiogram, has provided a more accurate means of localizing the site of conduction abnormality in patients with various forms of heart block.4 '9 In addition, this technic has been utilized to study various physiologic20-24 and pharmacologic25-28 interventions, arrhythmias,29-31 and the Wolff-ParkinsonWhite syndrome.32 33 Published reports have contained a variety of terms applied to the various intervals representing conduction through the atrioven-