A new method has been developed for on-line noninvasive recording of the electrical activity within the P-R segment of the electrocardiogram (KG). The electrocardiogram is obtained using a bipolar chestwall lead. After amplication the signal is processed by a minicomputer. The signal-to-noise ratio of the signal is improved using the averaged response technique. Special care was taken to facilitate on-line man-machine communications. The user can monitor the averaging process with the aid of a point plot display of the data and a set of switches. The method was tested by comparing intracardiac electrograms of IO patients with their own surface recorded ECG's. This simplified and fast method gives the user information about conduction abnormalities in a noninvasive way. The method is evaluated in the clinic.
Intracardiac electrocardiography and electrical pacing are important diagnostic tools in the analysis of disturbances in the electrical conduction system of the human heart.
Recently a catheter technique (1, 2) for recording the His bundle activity as apparent in the P-R segment of the electrocardiogram, was introduced, and many studies on this specialized conduction system have been done. However the catheter technique has limitations, which complicate the use of the technique as a routine test. These limitations are (3) : (1) the facilities of a cardiac catheterization laboratory and a trained staff; (2) its invasive nature and therefore the inability to perform repeated sequential studies.
To circumvent these complications a method has been developed to record the small electrical activities of the His bundle in a noninvasive way (4). Reports that describe these methods have shown the feasibility of noninvasive or almost noninvasive detection of His bundle activities in dogs (5,6) and man (7,8). The method described in this paper, however, can in addition be applied on-line and real-time on human patients.
The small electrical activities within the His-Purkinje system will propagate to the body surface according to volume conductor theory (9). The potential at the chestwall is in the range of l-10 pV. Environmental noise which is in the same order of magnitude prevents a direct measurement of this potential through standard Copyright ' 9 1976 by Academic Press, Inc.