Introduction
Oesophagectomy is a complex procedure performed for malignant and benign conditions.
Procedural variations exist, dependent on patient and disease factors, with the stomach
typically being used for reconstruction. Postoesophagectomy conduit dysfunction is
common, including delayed gastric conduit emptying (DGCE) (approximately 30 per cent),
gastro-oesophageal reflux disease (approximately 80 per cent) and other chronic symptoms
without a mechanical cause
1,2
. Emerging evidence implicates abnormal gastric electrophysiology as a contributing
factor
3–5
.
Although conduit dysfunction is multifactorial, dysmotility is a common contributing
mechanism. However, it is clinically challenging to distinguish patients with dysmotility
as opposed to alternative causes for symptoms (for example obstruction or pyloric
dysfunction), as current tests such as endoscopy, fluoroscopy, radionuclear imaging
and manometry have limited accuracy, and/or are invasive or involve radiation. A safe
and accurate test is needed to reliably assess conduit motility to inform correct
therapy.
Gastric Alimetry® (Auckland, New Zealand) is a new non-invasive test to evaluate gastric
electrophysiology and function at high resolution, recently receiving regulatory approvals
for clinical use
6
. This technique has been extensively validated
3,7,8
and is being applied in medical disorders, but has yet to be used for postoperative
patients. This study therefore evaluated the feasibility of applying Gastric Alimetry
after oesophagectomy to assess conduit motility.
Methods
Patients who underwent oesophagectomy in Auckland, New Zealand, within the last 3
years were invited to participate following ethical approval (AH1125). Patients were
excluded if they were undergoing chemotherapy/radiotherapy, had not undergone postoperative
computed tomography (CT) or suffered mechanical obstruction. Clinical data including
operation notes, imaging, endoscopy and histopathology were evaluated.
Gastric Alimetry was performed under a protocol adapted for oesophagectomy. This device
comprises a high-resolution stretchable electrode array (8 × 8 electrodes; 20 mm spacing;
196 cm2), a wearable Reader, validated iOS app for symptom logging and a cloud-based
reporting platform (
Fig. 1
)
9–11
. Patients were fasted for >6 h before array placement as guided by gastric position
on CT (
Fig. 1a–e
). After a 30 min baseline recording, patients consumed a 218 kcal meal (100 ml nutrient
drink and half an oatmeal energy bar), followed by a 4-hour postprandial recording
with concurrent symptom logging.
Fig. 1
a Array placement in relation to the thoracoabdominal gastric conduit. b Coronal,
sagittal and axial views from CT scans of ID#1 illustrating the location of the stomach
located in the posterior mediastinum, behind the heart, lungs and liver. c Gastric
Alimetry stretchable electrode array. d Gastric Alimetry wearable Reader. e Gastric
Alimetry electrode array and wearable Reader on the patient’s thoracoabdominal region,
per the placement depicted in a. f Spectral map for Case ID#1 illustrating a reduced
principal gastric frequency and BMI-adjusted average amplitude. Patient photo and
imaging are used with patient's written consent. AgCl, silver chloride; TPU, thermoplastic
polyurethane.
Spectral analysis was performed, encompassing four established metrics
12
: principal gastric frequency, BMI-adjusted amplitude, Gastric Alimetry Rhythm Index
(GA-RI; reflecting pacemaker stability), fed:fasted amplitude ratio (ff-AR; indicating
meal response with contractions), with comparison to reference intervals
13
. Frequency was not reported if there was no rhythm (as measured by GA-RI)
10
. Adverse events were recorded. Data were evaluated with descriptive statistics.
Results
Demographic and operative data are reported in
Table S1
. Six patients were recruited (all males; median age 65.5 years; range 58–73). Oesophagectomies
were performed between 6.5 months and 3 years prior, with the standard procedure including
vagotomy and pyloroplasty. Indications were cancer (n = 4), Barrett’s oesophagus (n
= 1) and achalasia (n = 1). One case (ID#6) developed a necrotic gastric conduit prompting
resection, formation of cervical oesophagostomy and feeding jejunostomy on day 6 following
surgery, with subsequent colonic interposition graft with Roux-en-Y reconstruction
8 months later. This case served as a negative control.
All patients except one were largely asymptomatic at the time of testing. The symptomatic
patient (ID#5) reported moderate to severe nausea, vomiting, early satiation, abdominal
pain, reflux and a poor quality of life.
Gastric activity was successfully captured non-invasively in all cases (
Figs. 1
,
2
). Four cases (IDs#1–2, 4–5) had at least one abnormal parameter, all showing reduced
motility profiles (
Fig. 1f
,
Fig. 2a, c–e
). Of these, low or abnormal frequency was the most common abnormality (4/4 cases),
followed by low amplitude in 3/4, low GA-RI in 2/4 and low ff-AR in 1/4 (
Fig. 2e
). The symptomatic patient (ID#5) was found to have abnormalities in all four domains,
with symptoms being maximal when activity was weakest (
Fig. 2d, e
). ID#3 was the only case with normal parameters throughout (
Fig. 2b, e
), who had minimal gastric resection (<4 cm).
Fig. 2
a–d illustrates case ID#2 to ID#5’s spectral maps with associated symptom burden plots.
Quantitative analysis is presented in e with reference intervals as shown. Quantitative
results for case ID#1 shown in
Fig. 1f
are also presented in e. f Spectrogram for the patient with the colonic interposition
graft. g Box and whiskers graph for the quantitative results for case ID#1 to ID#5.
The dashed line represents the lower limit of the reference interval for each Gastric
Alimetry spectral metric. ff-AR, fed:fasted amplitude ratio; GA-RI, gastric alimetry
rhythm index.
In the negative control (ID#6), no gastric activity was identified, but low frequency
burst activity was evidence consistent with immediate colonic activity postprandially
(
Fig. 2f
)
14
.
No adverse reactions occurred.
Discussion
Persistent upper gastrointestinal symptoms in the absence of mechanical obstruction
are common after oesophagectomy. Contributing factors include conduit dysmotility,
hypersensitivity/pain syndromes, dumping syndrome and pyloric dysfunction, which may
overlap and are difficult to differentiate on clinical history and current tests.
This study shows the safety and feasibility of a new test called Gastric Alimetry
for non-invasively evaluating the function of the deep-seated postoesophagectomy gastric
conduit.
Gastric surgery modifies the electrical conduction system that coordinates contractions
15
, with previous studies implicating abnormal electrophysiology in conduit dysfunction
3–5
. However, reliable techniques to assess conduit function have been lacking. Recent
advances have enabled substantial progress in evaluating gastric electrophysiology
in health and disease
7,16,17
. A legacy technique termed electrogastrography (EGG) previously attempted to capture
gastric electrical activity from the skin surface, but was limited by low resolution
and high sensitivity to noise
5
. Gastric Alimetry overcomes these problems by employing a high-resolution array together
with sophisticated signal processing algorithms
9,10
, which were shown to be effective even with conduits positioned in the thorax and
posterior mediastinum. The patient with a total gastrectomy and colonic interposition
graft served as a negative control, further increasing confidence in the current findings.
Previously, Gastric Alimetry has been exclusively performed in patients with normal
gastric anatomies, in whom reference ranges were developed
12,13,17
. Some adjustments to interpretations will therefore be required as the test is applied
to postoperative patients. Specifically, normative values for amplitude will need
to be redefined due to the greater distance between the stomach and the array, and
this work is currently in progress. Additionally, meal sizes were reduced by 50 per
cent versus the standard Gastric Alimetry test to account for the reduced gastric
remnant volume, which is considered adequate to stimulate gastric activity
6
.
Reduced motility parameters were the dominant finding in this post-oesophagectomy
cohort, observed as reductions in frequency, rhythm stability (GA-RI) and meal responses
(ff-AR), except for one patient who had a minimal gastric resection. Reduced frequency
likely reflects resection of the native gastric pacemaker, leading to the development
of a new lower frequency pacemaker
18
. Low GA-RI likely reflects gastric neuromuscular dysfunction due to aberrant pacemaker
recovery
6
, while reduced meal responses could reflect loss of vagal input
15
. While vagotomy is inevitable to allow lymph node harvest in cancer patients, evolving
techniques that offer vagal-sparing oesophagectomies for non-malignant indications
(for example achalasia or stricturing disease) may assist in avoiding vagotomy-associated
complications
19
.
Validated symptom profiling is also performed with the Gastric Alimetry test. While
detailed symptom analysis was not a focus of this feasibility study, symptom profiling
is proving useful elsewhere in distinguishing cases with hypersensitivity and pain
syndromes, particularly when gastric function is normal, and is likely to be valuable
in future postoperative studies
6,11
. Emerging spatial mapping techniques will also allow determination of electrical
propagation patterns in future studies
9
.
With feasibility established, future studies can now be conducted applying this technique
on larger cohorts of patients after oesophagectomy. Such work will enable improved
characterization of pathophysiology and symptom correlations, in order to guide therapeutic
decisions, as is being performed in other gastric disorders
6
. In addition, the new test is also now being evaluated for its potential in gastric
dysfunction after pancreaticoduodenectomy
20
.
Supplementary Material
zrad036_Supplementary_Data
Click here for additional data file.