Inverse relation between patient age and chronic stimulation threshold in permanent endocardial ventricular pacing

The influence of age of the adult pacemaker patient upon postoperative threshold rise and chronic stimulation threshold was investigated by means of noninvasive threshold measurements in a group of 47 patients (aged 50 to 93 years), all provided with porous endocardial ventricular electrodes (Cardiac Pacemakers, Inc.) and Siemens-Elema Vario pulse generators. The voltage threshold recorded at implantation showed no age dependence; however, the threshold rise within 1 month after implantation, maximal recorded threshold, as well as the chronic threshold were inversely related to age--i.e., in older patients lower values were obtained. These results probably reflect a lesser local tissue reaction at the site of the electrode tip in the elderly. In the individual patient no relation could be found between stimulation threshold at implantation and maximal or chronic threshold.