[Use of intracardial R-potential measurement at pacemaker implantation (author's transl)].

The dislodgement rate of transvenous, endocardial pacemaker leads ranges between 7 and 11%. To evaluate the stability of the lead position, intraoperative measurements of the intracardial R-potential were performed via the positioned stimulating electrode. The intracardial R-potential demonstrated fluctuating amplitudes while those of the simultaneously recorded surface ECG remained constant. The fluctuations in amplitude were measured as delta-R. In the presence of only slight fluctuations in R-amplitude (delta-R 2.10 mV, SD = +/- 1.08 mV) the position of 250 electrodes was documented to be securely fixed. In the case of 23 electrodes with marked fluctuations in R-amplitude (delta R 6.68 +/- 1.7 mV) intraoperative dislocation occurred in spite of adequate positioning on fluoroscopy and low thresholds. In five patients failure of the pacing function occurred postoperatively; in this group the mean measured value of delta-R was 5.66 mV. Particularly small fluctuations in delta-R were observed in association with cork-screw electrodes and those which had been stabily positioned for a number of years; the mean value for the latter groups was 0.7 +/- 0.3 mV. The uniformity of the intracardial R-amplitude is primarily dependent on the mechanical stability of the electrode tip. Even slight geometrical changes may lead to notable amplitude fluctuations. In this study, measurement of the R-amplitude fluctuations to guide positioning of the electrode permitted a reduction of the dislodgement rate to 2%. Technically, the method does not require complicated instrumentation and is not time-consuming.