The final study group consisted of 117 generators. These generators were divided into 2 groups based upon the pacing mode used. There were 64 generators that were used for epicardial pacing and 53 for endocardial pacing. Group 1 was further subdivided based upon patient age at the time of generator implant. Age 4 years was chosen as the dividing age as above this age the resting heart is relatively constant and considerably lower than before age 4 years based upon heart rates of nirmal children. For those in group 1 who were less than 4 years there were 34 generators with a median patient implant age of 1.2 years. For those greater than 4 years old at implant there were 30 generators with a median implant age of 10.4 years. For the group 2 the median implant age was 14.8 years with a minimal implant age of 3.6 years.