Changes of Sympathovagal Balance Measured by Heart Rate Variability in Gastroparetic Patients Treated with Gastric Electrical Stimulation

Gastroparesis, a gastric motility disorder characterized by delayed gastric emptying without evidence of mechanical obstruction (Nilsson, 1996), clinically presents as nausea, vomiting, abdominal pain, with a compromised nutritional state. Gastroparesis has multiple etiologies but the dominant ones are diabetes (DM), idiopathic (ID) and post-surgical (P-S). Frequent hospital admissions, and severe symptoms make gastroparesis patients socially restricted (Soykan et al., 1998). Approximately one third of gastroparesis cases are caused by diabetes mellitus. Diabetic gastroparesis may be attributed to impaired motor activity involving gastric hypomotility and unpropagated contractions (lack of peristalsis) and/or impaired myoelectrical activity explained by abnormal frequency of the gastric slow wave (dysrhythmia), low amplitude and/or uncoupling of slow waves (You et al., 1980; Telander et al.,1978; Geldof et al.,1986; Chen et al., 1992). The most common treatment for gastroparesis is the use of prokinetic agents, such as metoclopramide, erythromycin and domperidone. However, only two agents are currently available in the USA, metoclopramide and erythromycin. Side effects from these agents result in up to 40% of patients being unable to tolerate chronic use (Sturm et al., 1999). Those who are refractory or intolerant to prokinetic agents often undergo abdominal surgery for the placement of a feeding jejunostomy tube which is only for nutritional support and does not improve gastric motility (Reardon et al., 1989; Ejskjaer et al., 1999). Gastric electrical stimulation (GES) is an emerging therapy for refractory gastroparesis. Currently two types of GES have been investigated for treatment of gastroparesis: (i) longpulse or high energy with low frequency stimulation and (ii) short-pulse or low energy with high frequency stimulation. Gastric electrical stimulation (GES) with short pulses and low energy (Enterra Device) was FDA approved in 2000 as a therapeutic option in the management of refractory gastroparesis (Familoni et al., 1997; Forster et al., 2001; Abell et al., 2002, 2003). Long-pulse and high energy stimulation, another approach to GES, achieves gastric pacing and represents a promising new treatment for gastric motility disorders (Hocking et al., 1992; McCallum et al., 1998; Lin et al., 1998). In this method, the electrical stimulus is composed of repetitive single pulses with a pulse width in the order of