Output programmability and reduction of secondary intervention after pacemaker implantation

Six hundred one new or initial pacemaker implants between Jan. 1, 1972, and Dec. 31, 1979, consisted of 289 output-programmable pulse generators and 312 fixed-output generators. Standard leads were used in all instances. Of the 289 output-programmable pulse generators, 4.5% (13) required revision for failure to capture the heart in the postimplant period; of the 312 fixed-output units. 9.6% (30) required revision (p = 0.015). In 41 patients the early threshold was above standard output (5 V. 10 mamp, 0.5 msec), and in six of them approximately 6 months were required to return to stable threshold levels below standard output. In the remainder, threshold rose above standard output and was managed by increased output of the output-programmable pulse generators, either briefly or permanently. We conclude that output programmability allows reduction in secondary intervention after implantation and that threshold evolution may occupy a period as long as 6 months.