CARDIAC PACING PROBLEMS IN INFANTS AND CHILDREN - RESULTS OF A 4-YEARPROSPECTIVE-STUDY

To evaluate cardiac pacing thresholds and the safety of a 2.5 V amplit ude setting, we prospectively studied 29 pediatric patients during a m ean follow-up of 16.4 months. Exit block (EB) at 2.5 V was confirmed d uring threshold analysis in 26% of 58 leads. No new cases were detecte d by threshold analysis after 20 weeks postimplantation. Exit block at 2.5 V occurred 4 times more frequently with ventricular than with atr ial leads (39% vs 8%) and 11 times more frequently with epicardial tha n with endocardial leads (47% vs 4%). There was no relationship betwee n intraoperative thresholds and EB during follow-up pacemaker checkups . The mean pulse width threshold (PWT) for endocardial ventricular lea ds was lower for steroid-tip than for non-steroid-tip leads (0.08 + 0. 01 msec vs 0.28 + 0.04 msec). Exit block did not occur with steroid-ti p leads. We conclude that during the first 20 weeks after implantation , a 2.5 V amplitude is not safe in children paced by means of nonstero id epicardial ventricular leads. Our approach to pacing in children in cludes (1) 5.0 V amplitude for epicardial leads during the first 20 we eks after implantation and (2) use of endocardial steroid-tip leads wh enever possible.