[Determination of first signs of pacemaker failure. Oscilloscopic study before and after removal].

An oscilloscopic study aimed at determining the first signs of pacemaker failure was carried out in vitro after removal in 95 cases. Using a differential apparatus with a 1 megahertz passing band, the following parameters were measured: interspike interval, amplitude, duration and morphology of the spike. During the course of the study, signs of pacemaker failure were seen in 66 cases. It may be concluded that the interspike interval represents the easiest and most precise measurement, making it possible alone to detect dysfunction in 70 per 100 of cases. However, in 30 per 100 of cases, represented by certain types of pacemaker, its alteration is preceded by a decrease in voltage. Whilst the latter may be precisely and easily measured in vitro, the same does not apply when the pacemaker is in situ and only large changes may be taken to be significant and interpreted in relation to the number of batteries in the model studied. Study of the vectrocardiogram should be added to the measurements mentioned above, any sudden change in axis of the spike being an argument in favour of a fault in the conductor. In the future, measurement of the area of the spike, a reflection of the energy delivered the histogram of the RR intervals giving an idea of the respective durations of function and of inhibition in demand models will provide additional information.