Multichannel intraluminal impedance for the assessment of post-fundoplication dysphagia

Devices for esophageal function testing

BACKGROUND AND AIMS

Esophageal function testing is an integral component of the evaluation of refractory GERD and esophageal motility disorders. This review summarizes the current technologies available for esophageal function testing, including the functional luminal imaging probe (FLIP), high-resolution esophageal manometry (HRM), and multichannel intraluminal impedance (MII) and pH monitoring.

METHODS

We performed a MEDLINE, PubMed, and MAUDE database literature search to identify pertinent clinical studies through March 2021 using the following key words: esophageal manometry, HRM, esophageal impedance, FLIP, MII, and esophageal pH testing. Technical data were gathered from traditional and web-based publications, proprietary publications, and informal communications with pertinent vendors. The report was drafted, reviewed, and edited by the American Society for Gastrointestinal Endoscopy Technology Committee and approved by the Governing Board of the American Society for Gastrointestinal Endoscopy.

RESULTS

FLIP is a high-resolution impedance planimetry system used for pressure and dimension measurement in the esophagus, pylorus, and anal sphincter. FLIP provides complementary information to HRM for esophageal motility disorders, especially achalasia. The Chicago classification, based on HRM data, is a widely adopted algorithmic scheme used to diagnose esophageal motility disorders. MII detects intraluminal bolus movement and, combined with pH measurement or manometry, provides information on acid and non-acid gastroesophageal reflux and bolus transit in patients with refractory GERD and for preoperative evaluation for anti-reflux procedures.

CONCLUSIONS

Esophageal function testing techniques (FLIP, HRM, and MII-pH) have diagnostic and prognostic value in the evaluation of esophageal motility disorders and refractory GERD. Newer technologies and classification systems have enabled an increased understanding of these diseases.

Evaluation of antireflux surgery using multichannel intraluminal impedance-pH measurement in neurologically impaired patients

PURPOSE

This study aimed to evaluate esophageal function before and after antireflux surgery (ARS) in neurologically impaired (NI) patients using 24 h multichannel intraluminal impedance (MII)-pH measurement.

METHODS

Seven NI patients (age, 0-33 years; median, 13 years) were assessed before and after ARS using 24 h MII-pH. We described reflux parameters such as pH reflux index, bolus exposure index, number of acidic and nonacidic reflux episodes, mean acid clearance time and median bolus clearance time, and esophageal motility parameters in dry swallows such as bolus presence time (BPT), total bolus transit time (TBTT), and total propagation velocity (TPV).

RESULTS

The postoperative reflux parameters such as pH reflux index, acid clearance time, bolus exposure index, and the number of acidic reflux episodes significantly decreased (P < 0.05) compared with the preoperative ones. The esophageal motility parameters including all sites of BPTs, TBTT, and TPV did not change in the MII-pH measurement after ARS (P = non-significant).

CONCLUSION

ARS effectively reduced gastro-esophageal reflux (GER) in NI patients without the impairment of esophageal motility by MII-pH measurement. MII-pH was useful to detect the subtype of GER before and after ARS and appeared to be appropriate for evaluating esophageal motility.

Impedance as an adjunct to manometric testing to investigate symptoms of dysphagia: What it has failed to do and what it may tell us in the future

Dysphagia is a common reason for referral for investigations of oesophageal motility. Impedance measurement has now been incorporated into commercially available diagnostic manometry systems for more than a decade. This innovation, which offered the ability to record patterns of bolus transport without the need for simultaneous radiology, has for the most part failed to live up to expectations, offering few additional diagnostic insights. This review examines the potential pitfalls related to how impedance patterns are currently analysed and introduces and discusses the new concept of pressure-flow analysis integrating pressure and impedance measurements to derive new metrics linked to the pressures occurring within and around the bolus as it is being transported.

Evaluating esophageal bolus transit by impedance monitoring

The function of the esophagus is transporting nutrients from the oropharyngeal cavity to the stomach. This is achieved by coordinated contractions and relaxation of the tubular esophagus and the upper and lower esophageal sphincter. Multichannel intraluminal impedance monitoring offers quantification of esophageal bolus transit and/or retention without the use of ionizing radiation. Combined with conventional or high-resolution manometry, impedance measurements complement the quantification of esophageal body contraction and sphincter relaxation, offering a more comprehensive evaluation of esophageal function. Further studies evaluating the utility of quantifying bolus transit will help clarify the role and position of impedance measurements.

Pre and post-operative evaluation of gastroesophageal reflux and esophageal motility in neurologically impaired children using combined pH–multichannel intraluminal impedance measurements

BACKGROUND

Gastroesophageal reflux disease (GERD) in patients with neurological impairment (NI) has not been fully studied before and after fundoplication procedure because their characteristics such as generalized gastrointestinal dysmotility, non-acid reflux, and the proximal reflux due to feeding of enteral nutrition via a nasogastric tube prevent their GERD from being detected by 24 h pH monitoring. The aim of this study was to elucidate whether multichannel impedance-pH measurement (pH/MII) is able to detect the subtypes of GERD and the differences in the reflux episodes of the severity of GERD, the ingestion pathway, and before and after fundoplication. The second aim was to determine whether a trial evaluation of dry swallows was able to be used to assess the esophageal motility of NI patients as an alternative examination.

PATIENTS AND METHODS

The 24 h pH/MII was conducted on 20 NI children [15 were the patients before Nissen's fundoplication (BN), of whom, six were fed orally (FO) and nine were fed via nasogastric tube (NGT), and five were the patients after Nissen's fundoplication (AN)]. All reflux episodes were evaluated and compared between patients with pathological GERD (PG) and non-pathological GERD (NG) and between patients who had FO and NGT and patients between BN and AN. Dry swallows were conducted to evaluate the esophageal motility. The average bolus presence time (BPT) and total bolus transit time (TBTT) were compared between the PG and NG, FO and NGT, and the BN and AN subgroups.

RESULTS

A total of 1,064 reflux episodes were detected by pH/MII. Of those, 303 (28.5 %) were non-acid-related and 477 episodes reached the proximal esophagus. Of the 12 patients (57.1 %) showing pathological GERD, two cases (16.7 %) demonstrated predominantly weakly acidic PG. More than half of the reflux episodes of PG patients reached to the proximal esophagus. The numbers of total reflux and proximal reflux episodes in the PG were significantly higher than those in NG patients. The number of proximal reflux episodes in the FO group was significantly higher than that in the NGT groups, whereas NGT patients showed more non-acidic reflux episodes than FO patients. A trial evaluation of dry swallows demonstrated no significant differences in this study.

CONCLUSION

The pH/MII was useful to detect the subtype of GERD in NI patients which could not be detected by 24 h pH monitoring. It can, therefore, be considered to have first priority for testing NI patients who are suspected to be suffering from GERD.

Dysphagia postfundoplication: more commonly hiatal outflow resistance than poor esophageal body motility

BACKGROUND

Historically, risk assessment for postfundoplication dysphagia has been focused on esophageal body motility, which has proven to be an unreliable prediction tool. Our aim was to determine factors responsible for persistent postoperative dysphagia.

METHODS

Fourteen postfundoplication patients with primary dysphagia were selected for focused study. Twenty-five asymptomatic post-Nissen patients and 17 unoperated subjects served as controls. Pre- and postoperative clinical and high-resolution manometry parameters were compared.

RESULTS

Thirteen of the 14 symptomatic patients (92.9%) had normal postoperative esophageal body function, determined manometrically. In contrast, 13 of 14 (92.9%) had evidence of esophageal outflow obstruction, 9 of 14 (64.3%) manometrically, and 4 of 14 (28.6%) on endoscopy/esophagram. Median gastroesophageal junction integrated relaxation pressure was significantly greater (16.2 mm Hg) in symptomatic than in asymptomatic post-Nissen patients (11.1 mm Hg, P = .05) or unoperated subjects (10.6 mm Hg, P = .02). Sixty-four percent (9/14) of symptomatic patients had an increased mean relaxation pressure. Dysphagia was present in 9 of 14 (64.3%) preoperatively, and elevated postoperative relaxation pressure was independently associated with dysphagia.

CONCLUSION

These data suggest that postoperative alterations in hiatal functional anatomy are the primary factors responsible for post-Nissen dysphagia. Impaired relaxation of the neo-high pressure zone, recognizable as an abnormal relaxation pressure, best discriminates patients with dysphagia from those without symptoms postfundoplication.

Dysphagia and gastroesophageal junction resistance to flow following partial and total fundoplication

BACKGROUND

Esophageal peristalsis and basal gastroesophageal junction (GEJ) pressure correlate poorly with dysphagia.

AIM

To determine intraluminal pressures that reflect GEJ function and to determine manometric correlates for dysphagia before and after fundoplication.

METHODS

The relationships between maximal intrabolus pressure, residual GEJ relaxation pressure and peak peristaltic pressure for water swallows were determined in normal volunteers and patients with reflux disease before and after fundoplication. GEJ anatomy was assessed by radiological, endoscopic and surgical criteria, whilst dysphagia was measured with a validated composite dysphagia score.

RESULTS

Dysphagia was significantly associated with lower peak peristaltic pressure in the distal esophagus and the presence of a hiatus hernia preoperatively, as well as higher residual pressure on GEJ relaxation postoperatively. Peak distal peristaltic pressure and residual GEJ relaxation pressure were predictors of intrabolus pressure after total fundoplication (p<0.002). Residual GEJ relaxation pressure was four times higher after 360° fundoplication (N=19) compared to 90° fundoplication (N=14, p<0.0001). Similarly, intrabolus pressure was elevated 2.5 times after 360° fundoplication and nearly doubled after 90° fundoplication and both were significantly different from controls (N=22) and reflux disease patients (N=53, p<0.0001).

CONCLUSIONS

Gastroesophageal junction impedance to flow imposed by fundoplication is associated with dysphagia when there is suboptimal distal esophageal contraction strength and relatively high residual GEJ relaxation pressure.

Swallow evaluation during multichannel intraluminal impedance and pH: an alternate method to assess esophageal transit

BACKGROUND

Twenty-four-hour multichannel intraluminal impedance and pH (MII-pH) esophageal monitoring allows detection of both acid and nonacid gastroesophageal reflux episodes. The MII-pH catheter contains 6 impedance segments placed 3, 5, 7, 9, 15, and 17 cm above the lower esophageal sphincter (LES), plus a pH electrode at 5 cm. Multichannel intraluminal impedance and esophageal manometry (MII-EM) allows both functional and manometric evaluation of the esophagus. The MII-EM catheter contains 4 impedance measuring segments (5, 10, 15, and 20 cm above LES) and 5 solid state pressure transducers (within the LES and 5, 10, 15, and 20 cm above LES). Five milliliter saline boluses are given in the recumbent position when performing an MII-EM study. In our laboratory, all patients have an MII-EM study performed before an MII-pH study. In many laboratories, MII-pH is done without earlier MII-EM.

AIM

To assess accuracy of swallows given before ambulatory MII-pH monitoring in detecting esophageal transit abnormalities.

MATERIALS AND METHODS

Hundred consecutive adult patients, prospectively studied (64 female; mean age = 52.6 y), presenting to our laboratory for MII-EM and 24-hours MII-pH study, also received 10 saline swallows in the recumbent position at the beginning of the MII-pH study. Impedance for these swallows was assessed for the presence of complete or incomplete transit; defined as presence of bolus entry in the 17 cm segment and bolus exit in the 15, 9, and 5 cm segments; defined by a rise in impedance above 50% between baseline and the nadir, and remaining above this value for at least 5 seconds. Of 10 swallows, the presence of 8 or more complete swallows satisfies the MII-EM criterion for diagnosis of complete transit. These findings were blindly compared with those of the 10 saline swallows on the MII-EM study.

RESULTS

In 93% of patients, the MII-pH swallows gave identical transit diagnosis to the MII-EM. In 2 patients, the diagnosis changed from incomplete transit on MII-EM to complete on MII-pH, and in 5 patients from complete transit on MII-EM to incomplete on MII-pH. With both methods, there were 64 patients with complete transit and 29 with incomplete transit. Thus, MII-pH swallows had a sensitivity of 94% and a specificity of 93% for detection of esophageal transit abnormalities.Comparing the swallow diagnosis for each patient, we found that there was a highly significant correlation (P < 0.0001) for the number swallows with complete (Pearson r = 0.89) and incomplete bolus transits (Pearson r = 0.89). There was also a significant correlation (P < 0.0001) in bolus transit time between both methods (Pearson r = 0.64).

CONCLUSIONS

Use of 10 saline swallows at the beginning of MII-pH studies is accurate, missing bolus transit abnormality in only 2 of 100 patients. It is also highly sensitive and specific for detection of esophageal transit abnormalities. This method allows detection of patients in whom further evaluation of esophageal function may be warranted.

High resolution manometry and multichannel intraluminal impedance oesophageal manometry in clinical practice

The past decade has seen new technological advances in the investigation of oesophageal motility disorders. Multichannel intraluminal impedance monitoring has been used as an adjunct to conventional manometry in the assessment of oesophageal function, independent of radiography. High resolution manometry provides additional information over conventional manometry, and its topographic analysis makes interpretation of studies easier. Both utilities in non-obstructive dysphagia have been used ultimately in research; however, more studies are addressing their clinical application.

Does combined multichannel intraluminal esophageal impedance and manometry predict postoperative dysphagia after laparoscopic Nissen fundoplication?

Laparoscopic Nissen fundoplication (LNF) is an effective treatment for gastroesophageal reflux disease; however, some patients develop dysphagia postoperatively. Manometry is used to evaluate disorders of peristalsis, but has not been proven useful to identify which patients may be at risk for postoperative dysphagia. Multichannel intraluminal impedance (MII) evaluates the effective clearance of a swallowed bolus through the esophagus. We hypothesized that MII combined with manometry may detect those patients most at risk of developing dysphagia after LNF. Between March 2003 and January 2007, 74 patients who agreed to participate in this study were prospectively enrolled. All patients completed a preoperative symptom questionnaire, MII/manometry, and 24-h pH monitoring. All patients underwent LNF. Symptom questionnaires were administered postoperatively at a median of 18 months (range: 6-46 months), and we defined dysphagia (both preoperatively and postoperatively) as occurring more than once a month with a severity >or=4 (0-10 Symptom Severity Index). Thirty-two patients (43%) reported preoperative dysphagia, but there was no significant difference in pH monitoring, lower esophageal sphincter pressure/relaxation, peristalsis, liquid or viscous bolus transit (MII), or bolus transit time (MII) between patients with and without preoperative dysphagia. In those patients reporting preoperative dysphagia, the severity of dysphagia improved significantly from 6.8 +/- 2 to 2.6 +/- 3.4 (P < 0.001) after LNF. Thirteen (17%) patients reported dysphagia postoperatively, 10 of whom (75%) reported some degree of preoperative dysphagia. The presence of postoperative dysphagia was significantly more common in patients with preoperative dysphagia (P= 0.01). Patients with postoperative dysphagia had similar lower esophageal sphincter pressure and relaxation, peristalsis, and esophageal clearance to those without dysphagia. Neither MII nor manometry predicts dysphagia in patients with gastroesophageal reflux disease or its occurrence after LNF. The presence of dysphagia preoperatively is the only predictor of dysphagia after LNF.

Randomized controlled trial of laparoscopic Nissen versus Lind fundoplication for gastro-oesophageal reflux disease

OBJECTIVE

To compare the effect of laparoscopic Nissen and Lind fundoplication on gastro-oesophageal reflux disease by means of a prospective randomized controlled trial.

MATERIAL AND METHODS

One hundred and twenty-one patients were randomized to undergo either Nissen (61) or Lind (60) fundoplication. Initial enrollment and subsequent clinical appointments were undertaken 1, 3, 6 and 12 months after the procedure using a standardized questionnaire. Ambulatory pH monitoring and manometry were undertaken both preoperatively and at approximately 3 months post-procedure.

RESULTS

The mean operating time was similar in both groups (44.8 versus 45 min). One operation in the Lind group was converted to open surgery. Postoperative dysphagia symptoms at 3 and 6 months were higher in the Nissen fundoplication group than in the Lind group (3 months p=0.003; 6 months p=0.020). The time taken to return to work was statistically longer in the Nissen group: at 1 month, 9 of 40 versus 2 of 45 patients had not returned to full activities (p=0.013). Three individuals required re-operation in the Nissen group and 4 individuals in the Lind group because of dysphagia caused by mechanical obstruction. Both procedures demonstrated good Visick scores at 12 months; the Nissen group having 33 (97%) patients with a Visick score of 1 or 2, and the Lind group having 38 (100%) patients with a Visick score of 1 or 2.

CONCLUSIONS

Both operations provide good quantitative and qualitative control of gastro-oesophageal reflux. Operation time and postoperative comparators were similar in both groups. There were no statistically significant differences between the groups at 1 year.

Long-term outcomes of revisional surgery following laparoscopic fundoplication

Background

A small proportion of patients who have laparoscopic antireflux procedures require revisional surgery. This study investigated long-term clinical outcomes.

Methods

Patients requiring late revisional surgery following laparoscopic fundoplication for gastro-oesophageal reflux were identified from a prospective database. Long-term outcomes were determined using a questionnaire evaluating symptom scores for heartburn, dysphagia and satisfaction.

Results

The database search found 109 patients, including 98 (5·6 per cent) of 1751 patients who had primary surgery in the authors' unit. Indications for surgical revision were dysphagia (52 patients), recurrent reflux (36), mechanical symptoms related to paraoesophageal herniation (16) and atypical symptoms (five). The median time to revision was 26 months. Outcome data were available for 104 patients (median follow-up 66 months) and satisfaction data for 102, 88 of whom were highly satisfied (62·7 per cent) or satisfied (23·5 per cent) with the outcome. Patients who had revision for dysphagia had a higher incidence of poorly controlled heartburn (20 versus 2 per cent; P = 0·004), troublesome dysphagia (16 versus 6 per cent; P = 0·118) and a lower satisfaction score (P = 0·023) than those with recurrent reflux or paraoesophageal herniation.

Conclusion

Revisional surgery following laparoscopic fundoplication can produce good long-term results, but revision for dysphagia has less satisfactory outcomes.

Review article: intra-oesophageal impedance monitoring for the assessment of bolus transit and gastro-oesophageal reflux

BACKGROUND

Intra-oesophageal impedance monitoring can be used to assess the clearance of a swallowed bolus (oesophageal transit) and to detect gastro-oesophageal reflux independent of its acidity.

AIM

To discuss the clinical application of the impedance technique for the assessment of bolus transit and gastro-oesophageal reflux.

METHODS

Review of the literature on intra-oesophageal impedance monitoring of bolus transit and gastro-oesophageal reflux.

RESULTS

Using impedance criteria, normal oesophageal bolus clearance can be defined as complete clearance of at least 80% of liquid boluses and at least 70% of viscous boluses. Impedance recording identifies oesophageal function abnormalities in non-obstructive dysphagia patients and in patients with postfundoplication dysphagia. The impedance technique seems to be less suitable for the most severe end of the dysphagia spectrum like achalasia. Intra-oesophageal impedance monitoring detects reflux events independent of the pH of the refluxate, which allows identification of non-acid reflux episodes. In addition, use of impedance monitoring enables assessment of the composition (liquid, gas, mixed) and proximal extent of the refluxate. Combined impedance-pH monitoring is more accurate than pH alone for the detection of both acid and weakly acidic reflux. Furthermore, addition of impedance monitoring to pH increases the yield of symptom association analysis both in patients off and on proton pump inhibitor therapy.

CONCLUSIONS

Intra-oesophageal impedance monitoring is a feasible technique for the assessment of bolus transit and gastro-oesophageal reflux. Combined impedance-manometry provides clinically important information about oesophageal function abnormalities and combined impedance-pH monitoring identifies the relationship between symptoms and all types of reflux events regarding acidity and composition.

Impedance detected abnormal bolus transit in patients with normal esophageal manometry. Sensitive indicator of esophageal functional abnormality?

When used in combination with manometry, multichannel intraluminal impedance better characterizes the established manometric abnormalities into those with and without associated transit defects. However, the significance of the finding of normal manometry and abnormal impedance is not known. The objective of this study is to evaluate the clinical relevance of abnormal impedance associated with normal manometry during esophageal function testing in patients with a variety of esophageal symptoms. All patients referred for esophageal function testing during a 27-month period underwent combined multichannel intraluminal impedance and esophageal manometry studies including 10 liquid and 10 viscous swallows in supine position. From 576 patients with normal esophageal body manometry we identified 158 patients (27%) with abnormal impedance. The primary symptom in these 158 patients was compared to that in 146 consecutive patients with normal manometry and normal impedance selected from the original 576 patients. Abnormal bolus transit was found with viscous, liquid and both type swallows in 60%, 19% and 21% of the patients respectively. Of patients with abnormal bolus transit, 23% presented with dysphagia compared to 10% of normal transit patients (p = 0.0035). In conclusion, abnormal impedance even in patients with normal manometry may be a sensitive indicator of esophageal functional abnormality as represented by the symptom of dysphagia in these patients. Abnormal transit was more frequently identified with viscous than liquid swallows. Prospective studies to further clarify impedance detected transit defects in patients with normal manometry and the role of viscous swallows in diagnostic testing are warranted.

Total fundoplication does not obstruct the esophageal secondary peristalsis: investigation with pre- and postoperative 24-hour pH-multichannel intraluminal impedance

AIM

To determine the impact of total fundoplication on the spontaneous esophageal clearance, known as secondary peristalsis.

BACKGROUND

Although there is general agreement that total fundoplication is not an obstacle to bolus swallowing (primary peristalsis), whether it is an obstacle to spontaneous esophageal clearance (secondary peristalsis) is still not clear. Based on 24-hour monitoring, multichannel intraluminal impedance was used to calculate the time of spontaneous bolus clearance (BCT).

METHODS

Mean BCT was prospectively calculated in 15 consecutive patients before and after total fundoplication. BCT was calculated in seconds including all the gastroesophageal reflux episodes, whereas bolus swallows (solid meals and liquid swallows) were excluded from the analysis.

RESULTS

BCT was extrapolated from 1,057 episodes in the 623 h of study. Overall, BCT did not change after surgery (13.6 +/- 4 vs. 15.2 +/- 10 s; p = nonsignificant) and in the upright (12.2 +/- 3 vs. 16.5 +/- 7 s; p = nonsignificant) and recumbent position (22.9 +/- 9 vs. 23.0 +/- 9 s; p = nonsignificant).

CONCLUSIONS

In this study total fundoplication did not affect the BCT by combined 24-hour ph monitoring and multichannel intraluminal impedance.

Return of esophageal function after treatment for achalasia as determined by impedance-manometry

BACKGROUND

Treatment for achalasia is aimed at the lower esophageal sphincter (LES), although little is known about the effect, if any, of these treatments on esophageal body function (peristalsis and clearance). We sought to measure the effect of various treatments using combined manometry (peristalsis) with Multichannel Intraluminal Impedance (MII) (esophageal clearance).

METHODS

We enrolled 56 patients with Achalasia referred to the University of Washington Swallowing Center between January 2003 and January 2006. Each was grouped according to prior treatment: 38 were untreated (untreated achalasia), 10 had undergone botox injection or balloon dilation (endoscopic treatment), and 16 a laparoscopic Heller myotomy. The preoperative studies for 8 of the myotomy patients were included in the untreated achalasia group. Each patient completed a dysphagia severity questionnaire (scale 0-10). Peristalsis was analyzed by manometry and esophageal clearance of liquid and viscous material by MII.

RESULTS

Mean dysphagia severity scores were significantly better in patients after Heller Myotomy than in either of the other groups (2.0 vs. 5.3 in the endoscopic group and 6.5 in untreated achalasia, p < 0.05). Peristaltic contractions were observed in 63% of patients in the Heller myotomy group, compared with 40% in the endoscopic group and 8% in untreated achalasia (p < 0.05 for both treatment groups vs. untreated achalasia). Liquid clearance rates were significantly better in both treatment groups: 28% in Heller myotomy and 16% in endoscopic treatment compared to only 5% in untreated achalasia (p < 0.05). Similarly, viscous clearance rates were 19% in Heller myotomy and 11% in endoscopic treatment, vs. 2% in untreated achalasia (p < 0.05). In the subset of patients who underwent manometry/MII both pre- and postoperatively, peristalsis was observed more frequently postoperatively than in preop studies (63% of patients exhibiting peristalsis vs. 12%), as was complete clearance of liquid (35% of swallows vs. 14%) and viscous boluses (22% of swallows vs. 14%). These differences were not significant, however. In the patients who had a myotomy the return of peristalsis correlates with effective esophageal clearance (liquid bolus: r = 0.46, p = 0.09 and viscous bolus: r = 0.63, p < 0.05). There is no correlation between peristalsis and bolus clearance in the endoscopic treatment group.

CONCLUSIONS

With treatment Achalasia patients exhibit some restoration in peristalsis as well as improved bolus clearance. After Heller Myotomy, the return of peristalsis correlates with esophageal clearance, which may partly explain its superior relief of dysphagia.