Predictive value of ST segment elevation in cardiac pacing.

In 366 pacemaker patients the influence of intracardiac ST segment elevation on the fate (displacement or perforation) of permanent cardiac pacemaker electrodes was studied. In one group of patients a retrospective analysis was carried out, the operator being aware of the degree of ST segment elevation and positioning the electrode to avoid very high or vey low values wherever possible. In the second group a prospective trial was carried out. The final electrode position was determined solely by fluoroscopy and electrical threshold, and the ST segment shift measured afterwards. The combined rates of electrode displacement and perforation did not differ between these groups. High levels of ST segment elevation, greater than 10 mV, were found to predispose to electrode perforation. On the other hand, low ST segments did not predict a displacement. It is concluded that the ideal positioning technique should seek a low electrical threshold, a stable position, and avoid high ST elevation.