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CLINICAL GASTROENTEROLOGY AND HEPATOLOGY 2005;3:49–54

linical Response to Gastric Electrical Stimulation in Patientsith Postsurgical Gastroparesis

ICHARD MCCALLUM,* ZHIYUE LIN,* PAUL WETZEL,* IRENE SAROSIEK,*nd JAMESON FORSTER‡

epartments of *Medicine and ‡Surgery, University of Kansas Medical Center, Kansas City, Kansas

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ackground & Aims: The aim of this study was to reporthe long-term clinical response to high-frequency gastriclectrical stimulation (GES) in 16 patients with postsur-ical gastroparesis who failed standard medicalherapy. Methods: Clinical data collected at baseline andfter 6 and 12 months of GES included (1) severity andrequency of 6 upper gastrointestinal (GI) symptoms bysing a 5-point symptom interview questionnaire andotal symptom score, (2) health-related quality of lifencluding physical composite score and mental compos-te score, (3) 4-hour standardized gastric emptying of aolid meal by scintigraphy, and (4) nutritional status.esults: The severity and frequency of all 6 upper GIymptoms, total symptom score, physical compositecore, and mental composite score were significantly im-roved after 6 months and sustained at 12 months (P <

05). All patients had delayed gastric emptying at baseline.astric emptying was not significantly faster at 12 months,lthough 3 normalized. At implantation, 7 of 16 patientsequired nutritional support with a feeding jejunostomyube; after GES, 4 were able to discontinue jejunal feeding.he mean number of hospitalization days was significantlyeduced by a mean 25 days compared with the prior year.ne patient had the device removed after 12 monthsecause of infection around the pulse generator.onclusions: Long-term GES significantly improved upperI symptoms, quality of life, the nutritional status, andospitalization requirements of patients with postsurgicalastroparesis. Although vagal nerve damage or disruptionas part of the underlying pathophysiology, GES therapyas still effective and is a potential treatment option for

he long-term management of postsurgical gastroparesis.controlled clinical trial of GES for PSG patients (who are

efractory to medical therapy) is indicated given thesencouraging results.

ostsurgical gastroparesis (PSG), identified as achronic form of gastric atony in the absence of

echanical obstruction that results from disruption ofhe normal mechanisms that govern gastric motility,evelops in up to 10% of patients who undergo vagot-

my (either deliberate or inadvertent) as part of their

pper gastrointestinal (GI) surgery.1–3 The incidencencreases to as high as 50% in those with chronic gastricutlet obstruction before surgery.4,5 Other surgeries thatre associated with delayed gastric emptying (GE) in-lude Billroth I and II antral resections, Roux-en-Y gas-rojejunostomy, fundoplication, esophagectomy with co-on or gastric pull-up, and pylorus-preserving Whipplerocedure.6 Associated symptoms include nausea, vom-ting, early satiety, abdominal pain, and weight loss.evere gastroparesis might result in recurrent hospital-zations, malnutrition, and significant mortality.1,7

Symptomatic management of PSG includes dietaryanipulation and the combination of prokinetic and

ntiemetic agents.3,8,9 However, only metoclopramidend erythromycin are commercially available in thenited States, and both have side effects that make them

ntolerable for more than 40% of patients.10 Without anntrum, medical therapies are less successful, and medi-ations might not be reliably absorbed because of bezoarormation.6,11 In severe cases, patients might be placedn a liquid caloric diet. For patients who fail theseherapies, surgical interventions are often contemplat-d.11 These include tube gastrostomy for gastric decom-ression and jejunostomy for enteral feedings. Total gas-rectomy is reserved for intractable vomiting and weightoss after all other options have failed. This is usually inhe patient after partial gastric resection with either aillroth I or II with or without a Roux-en-Y reconstruc-

ion.Recently, gastric electrical stimulation (GES) has been

nvestigated as a new approach for treatment of medicallyefractory gastroparesis.12,13 Several studies have shownhat GES by an implantable device with high-frequency

Abbreviations used in this paper: GE, gastric emptying; GES, gastriclectrical stimulation; HQOL, health-related quality of life; MCS, mentalomposite score; PCS, physical composite score; PSG, postsurgicalastroparesis; TPN, total parenteral nutrition.

© 2005 by the American Gastroenterological Association1542-3565/05/$30.00

PII: 10.1053/S1542-3565(04)00605-6

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50 MCCALLUM ET AL. CLINICAL GASTROENTEROLOGY AND HEPATOLOGY Vol. 3, No. 1

12 cycles/min) and low-energy stimulation parameters330 �s and 5 mA) produced a significant and sustainedmprovement in symptoms and nutritional status in

ost patients with intractable symptomatic gastropare-is.14–18 On the basis of the WAVESS data,16 the USood and Drug Administration approved GES with highrequency and low energy parameters (ENTERRA Ther-py System; Medtronic, Minneapolis, MN) in March000 under a Humanitarian Device Exemption forymptomatic relief in patients with diabetic and idio-athic gastroparesis, but not for postsurgical etiologies.19

here are only 2 preliminary reports of GES therapy inatients with PSG.20,21 However, these 2 studies areerformed in a small group of PSG patients with variousurations of GES therapy, thus underpowering the sta-istical analysis of the clinical effects of GES. In thisresent report, we analyzed the clinical response after 12onths of GES therapy in patients with PSG, including

ymptoms, health-related quality of life (HQOL), nutri-ional status, and GE.

MethodsPatients

There were 16 patients (15 women and 1 man; meange, 46 years; range, 21–66 years) who underwent GES im-lantation for documented refractory PSG between 2000 and003 at the University of Kansas Medical Center, Kansas City,ansas. The key inclusion criteria were (1) documented diag-osis of gastroparesis for more than 1 year and refractoriness tontiemetics and prokinetics; (2) more than 7 emetic episodeser week; (3) in the setting of fundoplication where patientsan not vomit then chronic daily nausea was the criterion; and4) delayed GE (gastric retention greater than 60% at 2 hoursnd greater than 10% at 4 hours) based on a 4-hour standard-zed radionuclide solid meal.22 Patients were excluded if theyad organic obstruction or pseudo-obstruction, primary eatingr swallowing disorders, chemical dependency, positive preg-ancy test result, or psychogenic vomiting. The study protocolas approved by the Human Subjects Committee at Univer-

ity of Kansas Medical Center, and written consent forms werebtained from all subjects before the study.

Study Protocol

This study consisted of (1) a baseline (the 4-weekeriod before surgery) evaluation of medical history and upperI symptoms, GE test, HQOL, assessment of nutritional

tatus, pregnancy testing, and blood chemistries to determinehe qualification for enrollment; (2) surgical placement of theES system by laparotomy as previously described if the

tomach is intact15,16 or position of the 2 electrodes in theuscularis propria of the greater curvature at 2 and 3 cm

roximal to the gastric anastomosis in the case of antrectomy;

3) removal of any parenteral nutrition, gastric decompression a

evices, or gastrically placed jejunal feeding tubes and (4) inases of malnutrition placement of a feeding jejunostomy tubef not already in place; and (5) follow-up at 6 and 12 monthsfter implantation to repeat baseline measurements. In addi-ion, adverse events, including hospitalizations, were moni-ored throughout the follow-up period. The detailed descrip-ions of the GES system and surgical and stimulationechniques have been published previously.15,16

Assessment of Symptoms

Each patient completed a Symptoms Interview Form ataseline and at 6- and 12-month follow-up visits. This formssessed the symptoms of gastroparesis occurring during theast 2 weeks before the interview for severity and frequency ofomiting, nausea, early satiety, bloating, postprandial fullness,nd epigastric pain. The severity of each symptom was gradedy the patients as 0, absent; 1, mild (not influencing the usualctivities); 2, moderate (diverting from, but not urging mod-fications of, usual activities); 3, severe (influencing usual ac-ivities, severely enough to urge modifications); and 4, ex-remely severe (requiring bed rest). Also the frequency of eachymptom was graded as 0, absent; 1, rare (1/wk); 2, occasional2–3/wk); 3, frequent (4–6/wk); and 4, extremely frequent�7/wk). The sum of the severity ratings of the 6 symptomubscores comprised the overall total symptom score (TSS) foreverity, and the sum of the frequency ratings of the 6 symp-om subscores comprised the overall TSS for frequency.

Assessment of Health-Related Quality ofLife

HQOL was assessed by using the previously validatedF-36 Health Status Survey (acute) questionnaire.23 Two sum-ary scores were derived from the 8 subscores of the SF-36

uestionnaire and reported as the physical composite scorePCS) and the mental composite score (MCS). PCS and MCSre norm-based measures for which the mean � standardeviation for the general US population is 50 � 10.24

Measurement of Gastric Emptying

GE scintigraphy was performed in the morning after anvernight fast as previously described22 with prokinetics stoppedor at least 3 days. This standardized method for GE consists of acrambled egg substitute (120 g of Free Cholesterol & Fat Freegg; Sunny Fresh Foods, Inc, Monticello, MN) (60 kcal) labeledith 99m Tc sulfur-colloid (1 mCi), 2 slices of whole wheat bread

120 kcal), 30 g jelly (75 kcal), and 120 mL of water.22 The mealas a total caloric value of 255 kcal (nutritional composition: 72%arbohydrate, 24% protein, 2% fat, and 2% fiber). Anterior andosterior images of the stomach were taken immediately afterating and then hourly for 4 hours. Gastric retention of gammaounts was calculated by the Department of Nuclear Medicine bysing geometric and decay correction. Delayed GE was defined ashe percentage of gastric retention equal to or greater than 60%

t 2 hours and equal to or greater than 10% at 4 hours or both.22

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Statistical Analysis

The symptom subscores, TSS, PCS, MCS, bodyeight, and hospitalization days, reported as means � stan-ard error, at baseline and at 6 and 12 months of GES wereompared by analysis of variance and paired t test analysis. The

ilcoxon signed rank test was used for paired comparison ofE. Results of GE are reported as median and interquartile

ange. Statistical significance was assigned for P value �.05.

ResultsBaseline Demographics

The mean duration of gastroparetic symptomsas 5.6 years (range, 1–33 years). On average the pa-

ients had lost 13.6 kg (range, 0–27.2 kg) and wereospitalized for a mean of 31 days (range, 0–200 days) inhe year before the GES. Six patients were enterallyupplemented through a variety of feeding tubes, and 2ere receiving total parenteral nutrition (TPN). Fifteenatients had delayed solid GE at baseline (Table 1). Theemaining patient could not complete the GE studyecause of vomiting, but she was included in this studyn the basis of her clinical history and prior abnormal GEesults from an outside medical center. The specific sur-ical procedures that preceded their symptoms and doc-mented gastroparesis in these 16 PSG patients are asollows: Nissen fundoplication (5), vagotomy and pylo-oplasty (3), Billroth I and vagotomy (2), Billroth II andagotomy (2), cholecystectomy (1), spinal surgery (2),

able 1. Patient Demographics and Baseline Measures

Patientno. Age (y) Sex BMI (kg/m2)

Years ofgastroparesis

1 66 F 25.2 22 60 F 18.0 43 64 F 17.2 334 31 M 30.8 35 45 F 23.5 106 46 F 33.2 47 57 F 20.4 1.58 21 F 14.0 3.59 37 F 33.8 1.5

10 49 F 31.8 211 34 F 21.3 112 27 F 22.7 1.513 36 F 28.2 3.514 53 F 18.0 1515 58 F 25.9 216 49 F 18.6 1.5

46 � 3 23.9 � 1.6 5.6 � 2.0

OTE. GE results (% retention) are reported as median and interquarMI, body mass index; J-tube, jejunostomy tube; N/A, not available;

nd esophagectomy with colonic interposition (2). d

Upper Gastrointestinal Symptoms

The results of upper GI symptoms are summa-ized in Table 2. In comparison with baseline, all 6 meanymptom severity subscores (vomiting, nausea, early sa-iety, bloating, postprandial fullness, and epigastric pain)ecreased �50% at 6 months of GES. The mean severityf nausea and epigastric pain also decreased �50% at 12onths compared to baseline. Both total symptom se-

erity and frequency were significantly reduced at 6onths of GES and sustained at 12 months compared to

he initial baseline (P � .05). In reviewing the Symptomnterview Form at 12 months of follow-up, 10 patients63%) had a �50% decrease in TSS.

Health-Related Quality of Life

At baseline, mean PCS and MCS scores (28.6 and9.7, respectively; Table 2) were substantially below theS norm (50 � 10),23 and both scores significantly

mproved at 6 and 12 months (P � .05). The majority ofhe improvement was observed within the first 6 months.pecifically, the MCS increased to 49.1 at 6 months,pproaching normal.

Hospitalizations

Hospitalizations for gastroparesis symptoms aver-ged 31 � 13 days (range, 0–200 days) for the yearefore receiving GES therapy. This average significantly

Gastric retentionat 4 hr (%)

1 y before GES

Nutritionalsupport

Days inhospital

Weight loss(lb)

35 0 3588 16 3022 0 3056 30 30 J-tube32 50 20 J-tube33 0 043 16 40 TPN34 7 14 J-tube57 40 4028 0 50

N/A (vomited) 100 4875 0 40 TPN78 200 60 J-tube93 30 30 J-tube52 0 0 J-tube75 0 0

52.0(34.0–75.0)

31 � 13 30 � 4

nge. All other measures are reported as means � standard errors.total parenteral nutrition.

tile ra

ecreased to 6 � 2 days (range, 0–29 days) (P � .05)

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52 MCCALLUM ET AL. CLINICAL GASTROENTEROLOGY AND HEPATOLOGY Vol. 3, No. 1

uring the first year of GES, and 8 patients (50%)equired no hospital admissions.

Gastric Emptying

Although both 2- and 4-hour median gastric reten-ion at 6 and 12 months was numerically less than that ataseline, they were not statistically different (Table 2). Ofhe 13 patients who completed the GE test at 12 months,

(23%) did normalize their GE, whereas all others re-ained delayed including 4 patients (31%) whose gastric

etention actually worsened. Of the 3 patients with no GEesults at 12 months, one did not finish because of vomitinghour after eating test meal, one was too sick to undergo

he test, and one was interviewed by telephone.

Nutritional Status

At implantation, 7 of 16 patients required nutri-ional support in the form of a feeding jejunostomy tube.f these 7 patients, 4 were able to discontinue the

ejunal feeding at 2, 4, 6, and 11 months after GES, andstill required supplemental feeding at 12 months.

verage body weight increased by more than 3 kg at 6onths and continued at 12 months (60.8 � 4.7 kg vs

4.2 � 4.5 kg vs 64.5 � 4.3 kg, respectively; P � .05ompared to baseline).

Adverse Events Related to Gastric ElectricalStimulation Therapy

One patient had the device removed after 12

able 2. Summary of Results of Upper GI Symptom SeverityAfter Receiving GES Therapy

Severity score (0–4) Baseline (n � 16)

omiting 2.0 � 0.5ausea 3.4 � 0.2arly satiety 2.9 � 0.2loating 3.1 � 0.2ostprandial fullness 2.9 � 0.2pigastric pain 2.6 � 0.3SS of severity (0–24) 17.1 � 0.7Frequency score (0–4) Baseline (n � 16)omiting 2.1 � 0.5ausea 3.9 � 0.1arly satiety 3.7 � 0.2loating 3.4 � 0.2ostprandial fullness 3.5 � 0.2pigastric pain 2.7 � 0.4SS of frequency (0–24) 19.2 � 0.7HQOL Baseline (n � 16)

CS 28.6 � 2.1CS 39.7 � 3.1Gastric retention (%) Baseline (n � 15)

t 2 hours (range) 81.0 (70.0–92.0)t 4 hours (range) 52.0 (34.0–75.0)

P � .05 compared to baseline.

onths because of infection in the pocket of the pulse T

enerator. One patient had the implanted GES systemeplaced at 23 months postoperatively as a result of hernvolvement in an accident because the electrodes wereetached from the gastric muscle by the trauma. Herymptoms reappeared 7 days after the accident, and theoad impedance was found to be increased and exceed thepper limit. The abdominal x-ray showed dislodgmentf the proximal lead from its original location in theastric smooth muscle. On re-exploration, there wasonfirmation that one of the leads had become detached.he device and electrodes were replaced, and her symp-

oms improved very soon after replacement of the GESystem, and the load impedance returned to normal.

DiscussionThe patients in this study had a variety of surgical

rocedures. However, the outcome was documentedSG, characterized by delayed GE and postprandial nau-ea and vomiting. Although the operations differed, allad undergone a procedure that involved either a knownagotomy or the potential for accidental injury to theagus verve. They all had failed to respond to prokineticgents, and ultimately they had a GES system implantednd received high frequency GES for at least 1 year.

Previous studies have investigated the efficacy of highrequency GES in improvement of upper GI symptomsnd quality of life in patients with severe gastroparesis as

result of diabetes or with idiopathic etiology.14–18

Frequency, HQOL, and GE at Baseline, 6 and 12 Months

6 mo of GES (n � 16) 12 mo (n � 16)

0.5 � 0.2a 1.1 � 0.3a

1.4 � 0.3a 1.4 � 0.2a

1.3 � 0.3a 1.7 � 0.4a

1.3 � 0.3a 1.6 � 0.4a

1.3 � 0.4a 1.6 � 0.3a

1.1 � 0.3a 0.8 � 0.3a

6.9 � 1.3a 8.6 � 1.5a

6 mo of GES (n � 16) 12 mo (n � 16)0.6 � 0.3a 1.2 � 0.3a

1.8 � 0.3a 1.8 � 0.3a

1.3 � 0.3a 2.2 � 0.4a

1.6 � 0.4a 1.7 � 0.4a

1.8 � 0.4a 1.8 � 0.4a

1.1 � 0.3a 1.3 � 0.4a

7.9 � 1.3a 9.8 � 1.5a

6 mo of GES (n � 16) 12 mo (n � 15)40.2 � 1.9a 37.7 � 2.7a

49.1 � 3.6a 49.6 � 3.2a

6 mo (n � 12) 12 mo (n � 13)67.0 (51.0–87.0) 66.0 (51.0–90.0)34.0 (25.0–65.0) 40.0 (19.0–73.0)

and

here are only 2 preliminary publications reporting the

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January 2005 ELECTRICAL STIMULATION FOR POSTSURGICAL GASTROPARESIS 53

esults of GES in patients with PSG.20,21 The first onlyncluded 5 PSG patients followed for up to 6 months,nd there was no statistical analysis included in thattudy.20 The second reported our initial experience with2 PSG patients with various follow-up times (3onths–1 year).21 Therefore, the present study is the

rst to investigate the effects of high frequency GES in aelatively large group of patients with PSG for more than12-month period. Our results showed that long-termES improved the upper GI symptoms and HQOL asell as nutritional support and the need for hospitaliza-

ions. These results are consistent with previous studiesn the effects of GES in patients with diabetic or idio-athic gastroparesis.14–18

The mean gastric retention measured by a standard-zed 4-hour scintigraphy of a solid meal was not signif-cantly reduced at 6 or 12 months. The 4-hour gastricetention at 6 and 12 months was still 4 times normalalue, ie, markedly delayed. This observation is in agree-ent with previous reports,16,18 indicating no associa-

ion between changes in symptoms and GE in patientsith gastroparesis treated with high frequency GES.

ndividually, only 23% of patients evaluated at 12onths of GES had their 2- or 4-hour gastric retention

educed to a normal value. In contrast, McCallum et al.25

howed that low frequency and high energy GES for aeriod of 1–3 months significantly improved GE andeturned the majority of patients with gastroparesis67%) to normal, as well as reversing gastric dysrhyth-ia with enhancement of the gastric slow waves. Theajor difference between these 2 studies was the stimu-

ation parameters used. This suggests in the future thatifferent stimulation parameters will be needed to re-erse dysmotility in PSG.

The mechanisms by which the upper GI symptoms inSG patients were improved with GES remain to belucidated. Short-pulse GES, similar to the parameterssed in this study, was evaluated in a canine model bysing vasopressin to induce gastric dysrhythmias andomiting in both intact and vagotomized dogs.26 Short-ulse stimulation produced a significant reduction inomiting in intact animals but not in those with acuteagotomy. This observation might suggest that the an-iemetic effect of short-pulse stimulation was vagallyediated. The results of this present study and earlier

linical observations,17,20,25 however, indicate that GESs also effective in relieving symptoms in patients withSG, including those with vagotomy, suggesting thathe effects of GES might not be solely vagally mediated.

Diabetic patients with gastroparesis have benefited

ymptomatically from GES therapy in a double-blind

rial16 utilizing GES in the same parameters as our trial,s well as in another study utilizing different parameterslow frequency and high energy) in which stimulation ofastric smooth muscle also improved GE.25 The ad-anced diabetic patients treated in both of these reportsrequently had accompanying vagal dysfunction. Thisrovides further evidence that GES is still effective evenithout normal vagal nerve innervation or function.This study was not placebo controlled, so we cannot rule

ut that the impressive response observed after GES mightepresent a placebo response. In diabetic and idiopathicatients, a double-blind study did show that 1-month GESesulted in significantly better symptom improvement than-month sham,16 and further reports indicated that thisymptomatic response to GES is sustained in the majority ofnitial responders.17,18 Also in the present study our pa-ients had failed all medical therapy, and the ability of GESherapy to induce a sustained clinical improvement anduality of life for more than 12 months exceeds any placeboxpectations or possibilities.

In our initial study of high frequency GES in patientsith gastroparesis, we performed serosal recordings of gas-

ric electrical activity and concluded that high frequencyES did not normalize dysrhythmias while still achieving

ymptom reduction.27 Mechanisms other than motor stim-lation have been proposed to explain the reductions inausea and vomiting and include adrenergic and cholinergicunctions,28 fundic relaxation,29 GI hormones,30 and affer-nt brain stem pathways.31 It would have to be hypothe-ized in our patients that the afferent pathways to the brainre explained by regrowth of the vagal nerve fibers or theevelopment of collaterals, or that afferent signals are as-ending via the sympathetic nervous system.

In conclusion, long-term GES significantly improvedhe severity and frequency of upper GI symptoms, qual-ty of life, and nutritional and hospitalization status ofatients with postsurgical gastroparesis refractory toedical therapy. Although vagal nerve damage was part

f the underlying pathophysiology in these patients, GESherapy was still effective and is a potential treatment forhe long-term management of postsurgical gastroparesis.

controlled clinical trial of GES for PSG patients (whore refractory to medical therapy) is indicated given thesencouraging results.

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Address requests for reprints to: Richard W. McCallum, MD, Depart-ent of Medicine, Mail stop: 1058, University of Kansas Medical Center,

901 Rainbow Blvd, Kansas City, KS 66160. e-mail: rmccallu@kumc.edu;ax: (913)-588-3856.

Portions of the study were presented in abstract format at themerican Gastroenterological Association meeting in 2004.The authors would like to acknowledge the following individuals for

heir contributions: Sara Durham, Suzanne Denton, and Katherineoeser as well as faculty, fellows, and nursing staff in the Division ofastroenterology, Janet Kelly, RN, the operating room staff, and sur-ical residents. We also wish to acknowledge Dr Twillman in psychol-gy and pain management and the faculty and staff of the Nuclearedicine Department. We also thank Warren Starkebaum, PhD, at

edtronic as well as the Medtronic Gastroenterology Group.