This study aimed to investigate whether baseline EKG measures of vagal efficiency/insufficiency could predict responders to PENFS therapy. Data were drawn from a 4-week prospective, randomized controlled trial comparing PENFS to a sham device in adolescents with functional abdominal pain disorders.

Baseline findings

1. Vagal efficiency was not predictive of pain at baseline.
2. Treatment and sham groups did not differ in baseline pain.

Post-PENFS treatment

1. There was no change in sham or treatment group subjects with high vagal efficiency.
2. Treatment group subjects with low and moderate baseline vagal efficiency had reduced pain scores after 3 weeks of treatment with active PENFS.

Significance

1. Adolescents with functional abdominal pain and reduced VE have greater improvement in abdominal pain after only 3 weeks of PENFS compared with sham.
2. Functional abdominal pain disorders may involve abnormal autonomic control.

The effects of PENFS therapy may be strongest in those individuals with suboptimal autonomic control (vagal insufficiency).