Rectal pacing: Pacing parameters required for rectal evacuation of normal and constipated subjects

Background and purpose. Our previous studies have demonstrated that rectal electric waves start at the rectosigmoid junction (RSJ) and spread caudad a long the rectum, A rectosigmoid pacemaker was postulated to exist at the RS J, We also demonstrated that electric waves in rectal inertia are so scarce that a "silent" electrorectogram is recorded; the myoelectric activity in such cases was stimulated by an artificial pacemaker placed at the RSJ, For this article we investigated the pacing parameters necessary for rectal ev acuation in rectal inertia patients. Methods. The study comprised 24 patients with rectal inertia divided into t wo groups: study group (10 women, 6 men; mean age, 38.9 +/- 10.6 years) and control group (6 women, 2 men; mean age, 36.3 +/- 9.8 years), The main com plaint was infrequent defecation and straining at stools, Eight healthy vol unteers (6 women, 2 men; mean age, 37.2 +/- 9.4 years) with normal stool fr equency were included in the study. Through a sigmoidoscope, an electrode w as hooked to the RSJ (stimulating) and two electrodes were hooked to the re ctal mucosa (recording). Rectal electric activity was recorded before (basa l activity) and during electric stimulation of the RSJ electrode with an el ectrical stimulator delivering constant electric current of 5-mA amplitude and 200-ms pulse width. Results. In the healthy volunteers, rectal pacing effected increases in fre quency, amplitude, and velocity from a mean of 2.3 +/- 0.9 to 6.2 +/- 1.8 c ycles/min (P < 0.01), 1.2 +/- 0.6 to 1.7 +/- 0.8 mV (P < 0.05), and 4.1 +/- 1.2 to 6.3 +/- 1.7 cm/s (P < 0.05), respectively. No waves were recorded f rom rectal inertia patients at rest. Rectal pacing of the study group showe d pacesetter potentials with a mean frequency of 2.1 +/- 1.2 cycles/min, am plitude of 0.9 +/- 0.1 mV, and velocity of 3.3 +/- 1.6 ms. The control grou p, in whom the pacemaker was not activated, showed no electric activity. Conclusions. Rectal pacing succeeded in producing myoelectric activity in p atients with rectal inertia. It is therefore suggested that this method be applied for rectal evacuation in patients with inertia constipation. (C) 20 00 Academic Press.