ESOPHAGUS
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ORIGINAL CONTRIBUTIONS
nature publishing group
Refractory Heartburn: Comparison of Intercellular
Space Diameter in Documented GERD vs. Functional
Heartburn
Marcelo F. Vela, MD, MSCR1, Brandon M. Craft, MD1, Neeraj Sharma, MD1, Janice Freeman, RN1 and Debra Hazen-Martin, PhD2
OBJECTIVES:
Refractory heartburn despite acid suppression may be explained by ongoing gastroesophageal reflux
disease (GERD) or functional heartburn (FH), i.e., symptoms without evidence of GERD. Impedance–
pH monitoring (impedance–pH) detects acid and nonacid reflux and is useful for evaluating acidsuppressed, refractory patients. Intercellular space diameter (ISD) of esophageal epithelium measured by transmission electron microscopy (TEM) is a marker of epithelial damage present in both
erosive and nonerosive reflux disease. ISD has not been used to study refractory heartburn or FH. Our
aim was to compare ISD in healthy controls and refractory heartburn patients with GERD and FH.
METHODS:
In refractory heartburn patients (heartburn more than twice/week for at least 2 months despite proton
pump inhibitor (PPI) b.i.d.), erosive esophagitis and/or abnormal impedance–pH (increased acid
exposure or positive symptom index) defined GERD; normal esophagogastroduodenoscopy (EGD)/
impedance–pH defined FH. Asymptomatic, healthy controls had normal EGD and pH-metry. Mean
ISD in each subject, determined by blinded TEM of esophageal biopsies, was the average of 100
measurements (10 measurements in each of 10 micrographs).
RESULTS:
In all, 11 healthy controls, 11 FH, and 15 GERD patients were studied. Mean ISD was significantly
higher in GERD compared with controls (0.87 vs. 0.32 μm, P = 0.003) and FH (0.87 vs. 0.42 μm,
P = 0.012). Mean ISD was similar in FH and controls (0.42 vs. 0.32 μm, P = 0.1). The proportion
of patients with abnormal ISD was significantly higher for GERD compared with FH (60 vs. 9%,
P = 0.014).
CONCLUSIONS: ISD is increased in refractory heartburn patients with GERD but not those with FH. Our findings
suggest that measurement of ISD by TEM might be a useful tool to distinguish GERD from FH in
patients with refractory heartburn.
Am J Gastroenterol 2011; 106:844–850; doi:10.1038/ajg.2010.476; published online 21 December 2010
INTRODUCTION
Gastroesophageal reflux disease (GERD) is a common disorder.
Heartburn or acid regurgitation is experienced on a weekly basis
by nearly 20% of the US population, with an annual prevalence of
up to 59% (1). The current standard approach for a patient presenting with heartburn, the most typical symptom of GERD, is
to empirically prescribe proton pump inhibitors (PPIs), as long
as there are no alarm signs (dysphagia, bleeding, weight loss) that
would otherwise mandate esophagogastroduodenoscopy (EGD).
However, we are seeing increasing numbers of patients in whom
heartburn persists despite these medications. The reported proportion of patients with heartburn who do not respond to PPIs
varies among studies, partly because of differing definitions of
failure, dissimilar patient groups, and different dosing (q.d. or
b.i.d.). It has been estimated that failure to control symptoms
occurs in up to 40% of patients receiving a PPI once per day (2),
and ~25% of these patients may respond to an increase to twicedaily dosing (3).
In patients with persistent heartburn despite maximal PPI therapy, EGD is indicated as it will diagnose erosive esophagitis (EE,
which provides evidence of acid reflux) and exclude nonreflux
esophageal pathology (4). If EGD is negative, as is most often the
case, reflux monitoring to quantify reflux and assess its association with the patient’s symptoms is indicated. In acid-suppressed
1
Gastroenterology and Hepatology, Medical University of South Carolina, Charleston, South Carolina, USA; 2Pathology and Laboratory Medicine, Medical
University of South Carolina, Charleston, South Carolina, USA. Correspondence: Marcelo F. Vela, MD, MSCR, Section of Gastroenterology and Hepatology, Baylor
College of Medicine and Michael E. DeBakey VA Medical Center, 2002 Holcombe Boulevard (111D), Houston, Texas 77030, USA. E-mail: [email protected]
Received 6 October 2010; accepted 16 November 2010
The American Journal of GASTROENTEROLOGY
VOLUME 106 | MAY 2011 www.amjgastro.com
patients with ongoing heartburn, impedance–pH monitoring on
medication may be preferable as it enables detection of both acid
and nonacid reflux (i.e., pH ≥ 4, also termed weakly acidic reflux)
(5). Reflux monitoring in these patients may demonstrate that the
persistent symptoms are attributable to ongoing acid or nonacid
reflux, or no relationship between reflux and the patient’s complaint of heartburn. In patients with refractory heartburn, normal
EGD, and negative reflux monitoring, a diagnosis of functional
heartburn (FH) can be made (6). The treatment approach is different for patients with true underlying GERD as opposed to FH.
Therefore, making this distinction is important.
Dilation of intercellular space diameter (ISD) of the esophageal epithelium, measured by transmission electron microscopy
(TEM), has been shown to be an early morphological marker of
tissue damage in a GERD animal model that assessed permeability
and ISD in rabbit esophageal epithelium (7). Increased ISD was
subsequently demonstrated in esophageal biopsies from GERD
patients (8). A recent study found that symptomatic patients with
abnormal acid exposure, with or without EE, have increased ISD
on electron microscopy (9). In addition, treatment with acid suppression resulted in normalization of intercellular spaces and resolution of symptoms in a group of patients with heartburn and
abnormal acid exposure on pH monitoring (10). Measurement of
ISD to assess patients with persistent heartburn on PPI has not
been evaluated. Furthermore, whether dilation of the intercellular
spaces is found in patients with FH is not known.
The primary aim of our study was to compare ISD measured by
TEM of esophageal epithelium in healthy controls and two groups
of patients with refractory heartburn: (i) those with objective evidence of GERD on EGD and/or 24-h impedance–pH monitoring, (ii) those with FH (normal EGD and impedance–pH). Our
hypothesis was that ISD measured by electron microscopy is
higher among refractory heartburn patients with GERD compared
with those with FH or healthy controls. A secondary aim was to
compare the proportion of patients with abnormal ISD (defined
based upon normal values from the healthy controls) in patients
with GERD and FH.
METHODS
Study subjects
Eligible patients included subjects ≥18 years of age with persistent heartburn (substernal burning pain or discomfort) at least
three times per week while on PPI b.i.d., with or without a night
time H2-receptor antagonist for at least 2 months. Patients were
recruited from the outpatient gastroenterology clinic at the
Medical University of South Carolina. Healthy controls had no
previous or current history of heartburn or reflux symptoms,
no previous or current GERD medication use, negative 24-h pH
study, and normal EGD. Controls were recruited by advertisements in the Medical University Campus. The criteria for exclusion from the study were previous esophageal or gastric surgery,
esophageal cancer, eosinophilic esophagitis, achalasia, esophageal spasm, and conditions precluding standard EGD under conscious sedation.
© 2011 by the American College of Gastroenterology
Patients were categorized according to the findings of EGD
and impedance–pH. Patients with EE on EGD and/or abnormal
impedance–pH were categorized as GERD. An abnormal impedance–pH monitoring study was defined by increased esophageal
acid exposure time (AET) (11) and/or a positive symptom index
(SI), i.e., > 50% heartburn events associated with a reflux episode
(12). Those in whom both EGD and impedance–pH monitoring
were normal were considered FH.
The study protocol was approved by the Medical University of
South Carolina Institutional Review Board, and informed consent
was obtained from each subject.
Study conduct
Patients with refractory heartburn underwent EGD and 24-h
ambulatory impedance–pH monitoring while on their acidsuppressive medication. During EGD, esophageal biopsies were
obtained to rule out eosinophilic esophagitis by light microscopy;
additional distal esophagus biopsies were stored for subsequent
electron microscopy analysis. The two tests were generally performed during the same week, and no more than 2 weeks apart.
Based upon the findings of EGD and impedance–pH, the stored
biopsies of at least 11 consecutive patients with GERD and FH
were examined by electron microscopy for assessment of ISD in
a blinded fashion.
Healthy controls underwent ambulatory pH monitoring off
medication. If distal esophageal acid exposure was normal (percent time pH < 4 of < 4.2, 6.3, and 1.2% for the total, upright, and
recumbent periods, respectively (13)), they proceeded to EGD. If
EGD was normal, distal esophagus biopsies were obtained in 11
consecutive healthy controls for determination of ISD by TEM.
Study procedures
Impedance–pH monitoring. Patients were asked to continue their
acid-suppressive medication before and during impedance–pH
monitoring. On the day of testing, patients came to the laboratory after fasting for least 4 h. Impedance–pH monitoring was
performed with a 2.1-mm transnasal catheter with six impedance
measuring segments and one pH electrode (Sandhill Scientific,
Denver, CO). This enabled pH monitoring 5 cm above the lower
esophageal sphincter, and impedance measurements at 3, 5, 9, 15,
and 17 cm above the lower esophageal sphincter. The catheter was
connected directly to a data logger (Sleuth System; Sandhill Scientific) for continuous recording of pH and impedance. Patients
were discharged and returned for removal of the catheter 24 h after placement. Patients entered meal times, heartburn events, and
body position directly into the data logger as well as in a paper
diary during the 24-h recording.
The impedance–pH tracing was analyzed by the Autoscan
software (Sandhill Scientific), followed by manual editing. Meals
were excluded from the analysis. Impedance changes detected
reflux episodes, and pH changes defined the episode as acid (pH
decreased to < 4.0) or nonacid (pH remained ≥4.0), as previously
described (14). Normal distal esophageal acid exposure for these
patients on acid suppression was defined as percent time pH < 4
of < 1.3, 1.5, and 0.5% for the total, upright, and recumbent periods,
The American Journal of GASTROENTEROLOGY
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Vela et al.
respectively, based upon existing data in acid-suppressed healthy
controls (11). A SI (no. of heartburn episodes associated with
reflux/total no. of heartburn episodes) ≥50% was considered
to be positive (12).
EGD. EGD was performed under conscious sedation, using standard technique. When EE was present, it was graded according to
the Los Angeles classification (15). During EGD, esophageal biopsies were obtained to rule out eosinophilic esophagitis (these
were examined by light microscopy after routine hematoxylin and
eosin staining). Additionally, in all study subjects, four biopsies
were obtained from 5 cm above the esophagogastric junction; this
site was chosen as a way to standardize the sampling location in
the distal esophagus, following the approach of previous studies
(16). Biopsy samples were placed in glutaraldehyde and stored in
a refrigerator for subsequent TEM.
TEM. Distal esophageal biopsy specimens were fixed in osmium
tetroxide, dehydrated in graded alcohol, and embedded in araldite. Ultrathin sections from copper grids were poststained with
uranyl acetate and lead citrate. The specimens were examined and
photographed with a JEOL JEM1010 transmission electron microscope (JEOL, Tokyo, Japan) at ×5,000 magnification. A total
of 10 randomly selected fields from the suprabasal epithelial layer
were photographed for each patient for subsequent ISD measurement by computer-assisted morphometry, using the NIH ImageJ
software (National Institutes of Health, Bethesda, MD). Mean ISD
in μm was calculated by averaging the diameters in 10 random
transects (drawn perpendicular to the neighboring membranes)
in each of 10 photographs, for a total of 100 measurements, as
previously described by Tobey et al. (8). Measurement of ISD was
carried out in a blinded fashion, without knowledge of the subjects’ study group (healthy controls, GERD, or FH).
Statistics
Sample size was calculated in order to allow detection of a difference of at least 0.5 μm in the mean ISD among the three study
groups as compared by analysis of variance, assuming a s.d. of
0.4, based on previous studies (9). Based on an α of 0.05 and a
β of 0.80, it was determined that 11 patients were needed in each
group.
Mean ISD among the three study groups was compared by
analysis of variance with significance defined as P < 0.05. This was
followed by pair-wise comparisons through t-tests, with significance defined as P < 0.017 based upon Bonferroni correction for
multiple comparisons. The proportions of GERD and FH patients
with increased ISD were compared by Fisher’s exact test, with significance defined as P < 0.05.
RESULTS
A total of 30 patients with refractory heartburn and 15 healthy
controls were recruited; 26 patients and 11 controls completed the
study (Figure 1). Four patients were excluded: two did not complete the impedance–pH study, one underwent impedance–pH
The American Journal of GASTROENTEROLOGY
monitoring on q.d. instead of b.i.d. PPI, and one completed all
studies but electron microscopy was not obtained because of an
error in sample processing. Four healthy controls were excluded:
three had increased acid exposure on pH-metry, and one had an
esophageal nodule on EGD. Esophageal biopsies examined by
light microscopy were negative for eosinophilic esophagitis in all
patients. Of the 26 refractory heartburn patients who completed
the study, 11 were classified as having FH on the basis of normal
EGD and 24-h impedance–pH monitoring on medication. The
other 15 patients were classified as having GERD: 2 had EE, 2 had
increased distal esophageal AET (↑AET), 7 had a positive SI, 1
had both EE and ↑AET, and 3 had both positive SI and ↑AET.
One patient did not undergo impedance–pH monitoring (lost to
follow-up after EGD), but was classified as having GERD based
upon the presence of EE.
There were no age or gender differences among the three study
groups (Table 1). Hiatus hernia was more frequent in GERD
patients compared with healthy controls (47 vs. 0%, P = 0.01);
there was no difference in frequency of hiatus hernia in GERD
compared with FH.
Examples of electron micrographs showing normal and increased
ISD are shown in Figure 2. Mean ISD for the three study groups is
shown in Figure 3. ISD was significantly higher in GERD patients
compared with controls (0.87 vs. 0.32 μm, P = 0.003) and FH (0.87
vs. 0.42 μm, P = 0.012). There was no difference in mean ISD for
FH compared with controls (0.42 vs. 0.32 μm, P = 0.1).
The upper limit of normal ISD, defined by the 95th percentile
in the 11 healthy controls, was 0.68 μm. Using this cutoff, the proportion of patients with abnormal ISD was significantly higher
for GERD compared with FH (60 vs. 9%, P = 0.014). The results
of EGD and impedance–pH monitoring in GERD patients with
normal and abnormal ISD are shown in Table 2. It is noteworthy
that of the 15 GERD patients, 8 had EE or increased acid exposure
(alone or in combination), and 3 of these 8 patients had a positive SI. The other seven patients had a positive SI as the sole criteria for diagnosis of GERD. Six of the eight (75%) GERD patients
with esophagitis or abnormal acid exposure had an increased ISD,
and mean ISD for this group was 1.12 μm. In contrast, three of the
seven (42%) patients with only positive SI had increased ISD, and
mean ISD for this group was 0.59 μm.
DISCUSSION
Measurement of ISD in esophageal epithelium by electron microscopy has not been previously used in the evaluation of patients
who fail to respond to acid suppression, including those with FH.
In this prospective, blinded study we found that in comparison
with healthy controls, ISD was increased in refractory heartburn
patients with true underlying GERD (documented by EGD and/
or impedance–pH reflux monitoring), but not in those with FH
(i.e., normal EGD and impedance–pH). Therefore, our data suggest that measurement of ISD is a useful tool to distinguish GERD
from FH in patients with heartburn that persists despite treatment
with a PPI. These results have potentially important implications
in both the clinical and research arena.
VOLUME 106 | MAY 2011 www.amjgastro.com
Electron Microscopy in Patients With Refractory Heartburn
Abnormal EGD
or impedance–pH
Normal EGD
and pH-metry
Excluded
Impedance–pH not completed = 2
Excluded
Abnormal pH-metry = 3
Impedance–pH on q.d. PPI = 1
Abnormal EGD = 1
EM not completed = 1
Functional
heartburn
n = 11
Healthy
controls
n = 11
GERD
n = 15
EE = 2
↑AET = 2
SI-positive = 7
EE + ↑AET = 1
SI-positive + ↑AET = 3
Figure 1. Study subject recruitment. A total of 30 patients with refractory heartburn were recruited for the study; 11 were classified as having functional
heartburn on the basis of normal esophagogastroduodenoscopy (EGD) and 24-h impedance–pH monitoring on medication (impedance–pH), and 15
were classified as having gastroesophageal reflux disease (GERD) because of erosive esophagitis (EE), increased acid exposure time (↑AET), or a positive
symptom index (SI-positive), either alone or in combination. Four patients were excluded (two did not complete the impedance–pH study, one underwent
impedance–pH monitoring on q.d. instead of b.i.d. proton pump inhibitor (PPI), and one patient completed all studies but electron microscopy (EM) was
not obtained because of an error in sample processing). A total of 15 healthy controls were recruited; 4 were excluded (3 had increased acid exposure on
pH-metry, and 1 had an esophageal nodule on EGD).
Table 1. Study subject characteristics
Healthy controls
Functional
heartburn
GERD
No. of subjects
11
11
15
Mean age
(years)
41
47
46
Percent female
73%
82%
73%
No. with hiatus
hernia (%)
0 (0%)
3 (27%)
7 (46%)*
GERD, gastroesophageal reflux disease.
*P = 0.01 vs. controls.
In the clinical realm, the implications for management are that
patients who are classified as having FH (on the basis of normal
ISD) may benefit from non-GERD treatments such as visceral
analgesia with tricyclic agents (6), cognitive behavioral therapy
(17), or possibly hypnotherapy (18). In contrast, the presence of
increased ISD in refractory heartburn patients may suggest incompletely treated GERD. For these patients, therapies should aim to
improve reflux control, the options for which include further acid
suppression, pharmacological inhibition of transient lower esophageal sphincter relaxations with agents such as baclofen (a GABA-B
agonist) (19), or possibly antireflux surgery. Alternatively, it may be
attractive to approach these patients through treatment that is specifically directed at mitigating the dilation of intercellular spaces. A
recent small animal study published only in abstract form showed
that antioxidants, such as vitamin C and N-acetylcysteine, may
© 2011 by the American College of Gastroenterology
Normal
Increased intercellular space
diameter
Figure 2. Electron micrographs showing normal intercellular space
diameter (ISD) in a healthy volunteer (left) and increased ISD in a
gastroesophageal reflux disease (GERD) patient.
prevent intercellular space dilation in esophageal epithelium that is
exposed to weakly acidic solutions containing bile acids, designed
to mimic refluxate of acid-suppressed patients (20). Of course, the
usefulness of ISD as a marker of GERD in refractory heartburn
patients needs to be confirmed by additional studies.
The implications for research are that in terms of the pathophysiology of persistent symptoms despite acid suppression,
in some patients this form of treatment may be insufficient to
achieve epithelial healing (i.e., normalization of ISD). In support
of this notion is the fact that experimental short exposure of the
esophageal mucosa to not only acid (pH = 2) but also weakly acidic
(pH = 5) solutions resulted in dilation of intercellular spaces in
The American Journal of GASTROENTEROLOGY
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Healthy controls
n = 15
Refractory heartburn
n = 30
Normal EGD
and impedance–pH
847
Vela et al.
The upper limit of normal mean ISD (defined by the 95th percentile in the healthy controls) of 0.68 μm found in our study is
similar to previously reported values of 0.74 and 0.45 μm (9,16).
Earlier studies also found mean ISD in groups of untreated GERD
patients to range between 1.0 and 2.04 μm (8,10,16), somewhat
higher than the mean ISD of 0.87 μm in the GERD patients from
our study. It is possible that our GERD patients with refractory
heartburn had a partial response to acid suppression, as earlier
data have shown normalization of ISD in patients who achieve
symptom resolution after treatment with a PPI (10). Based upon
the upper limit of normal for mean ISD from our healthy controls, ISD was increased in 9 of 15 (60%) GERD patients and 1 of
11 (9%) FH patients. This would suggest that an increased ISD is
highly predictive of true underlying GERD as opposed to FH in
patients with refractory heartburn. On the other hand, six GERD
patients had normal ISD, implying that ISD may be normal even
when other tests suggest the presence of GERD. It is worth noting that eight patients were classified as having GERD because of
EE or increased acid exposure (see Table 2), whereas in the other
seven patients with GERD, the diagnosis was made based upon a
positive SI in the absence of EE or increased acid exposure. Mean
group ISD was higher and the proportion of patients with abnormal ISD was greater for patients with esophagitis or increased acid
exposure compared to those with only a positive SI as a marker
of GERD. However, the study was not designed or powered to
compare ISD in these subgroups of patients. Of course, EE and
increased acid exposure are considered more robust indicators
an animal model (21). It is noteworthy that weakly acidic reflux
is what one would expect the pH of refluxate to be in acid-suppressed patients. This finding was recently confirmed in healthy
human volunteers, in whom increased ISD was demonstrated following esophageal perfusion with acid and weakly acidic solutions
(22). This increased ISD could theoretically be implicated in the
persistence of symptoms in patients with refractory heartburn.
The reasons explaining why ISD normalizes in some, but not all,
patients after acid suppression will require further study. Another
potential implication for clinical investigation is that if additional
studies reinforce the value of ISD assessment in GERD patients,
this measure could provide a robust end point that can be used in
clinical trials examining the treatment of GERD, especially those
with refractory symptoms.
Intercellular
space diameter (μm)
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2
1.5
1
0.5
0
Controls
n = 11
Functional
heartburn
n = 11
GERD
n = 15
Figure 3. Scatter plot of mean intercellular space diameter (ISD) in μm for
the three study groups. GERD, gastroesophageal reflux disease.
Table 2. Results of EGD, impedance–pH, and TEM in GERD patients
EGD findings
GERD patient
1
Impedance–pH findings
TEM findings
Hiatus hernia (cm)
EE gradea
AET
SI
ISD (µm)
Increased ISD
5
D
Increased
No sym
0.94
Yes
b
2
5
B
b
1.17
Yes
3
2
D
Normal
Negative
1.77
Yes
4
2
0
Increased
No sym
1.18
Yes
5
6
0
Increased
Negative
1.45
Yes
6
0
0
Increased
Positive
0.32
No
7
3
0
Increased
Positive
1.87
Yes
8
0
0
Increased
Positive
0.24
No
9
4
0
Normal
Positive
1.13
Yes
10
0
0
Normal
Positive
0.24
No
11
0
0
Normal
Positive
1.09
Yes
12
0
0
Normal
Positive
0.24
No
13
0
0
Normal
Positive
0.94
Yes
14
0
0
Normal
Positive
0.27
No
15
0
0
Normal
Positive
0.18
No
AET, distal esophageal acid exposure time; EE, erosive esophagitis; EGD, esophagogastroduodenoscopy; GERD, gastroesophageal reflux disease; ISD, intercellular space
diameter; No sym, symptoms not reported during 24-h impedance–pH monitoring; SI, symptom index; TEM, transmission electron microscopy.
a
Esophagitis grade based upon the Los Angeles classification (15).
b
Patient did not undergo impedance–pH testing but was classified as having GERD based upon the presence of EE.
Bold entries signify that the particular measure is abnormal.
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of GERD compared with the SI, which has limitations (23). This
brings up the difficulty posed by the lack of a gold standard for
diagnosing GERD in endoscopy-negative patients, and it raises the
possibility that some of the patients in our study with normal ISD
in fact do not have GERD, presenting instead with a falsely positive
impedance–pH test because of a positive SI. Whether this is the
case, as opposed to the opposite (GERD documented by impedance–pH and a falsely negative assessment by electron microscopy
showing normal ISD), cannot be determined from our study. This
question can only be answered by future outcome trials designed
to assess and compare the ability of increased ISD vs. a positive SI
to predict response to treatment in GERD patients.
The strengths of our study include detailed characterization of
the study groups, adequate sample size, and blinded ISD assessment. All healthy controls were asymptomatic, and the possibility
of “silent GERD” was further excluded by EGD and 24-h pH monitoring. Patients with refractory heartburn were evaluated by the
best currently available diagnostic modalities (EGD and impedance–pH monitoring). The previously described differences in
ISD between patients and controls are large (9), thus allowing for
adequate power with a relatively small sample size. Determination
of ISD was performed in a blinded fashion, without knowledge of
the subjects’ underlying diagnosis.
A limitation of the study is that it does not provide information about whether increased ISD is specific to GERD, because
we did not have a group of patients with other esophageal disorders (e.g., eosinophilic esophagitis) for comparison. Some have
suggested that ISD may not be specific for GERD (24), although
data regarding this issue are limited. Increased ISD has been
shown to be present as the result of exposure to acute stress in an
animal model (25). Therefore, it would have been preferable to
include a validated measure of anxiety and stress to account for
this variable. Previously published clinical trials have supported
the presence of increased ISD as a marker of GERD, by finding
that it was present in patients with abnormal acid exposure but
negative EGD (8,9), that ISD normalized in parallel with the resolution of heartburn after PPI treatment (10), and that it could
be induced by esophageal perfusion with acid and weakly acidic
solutions in healthy controls (22). Whether obtaining biopsies
closer to the esophagogastric junction would result in improved
accuracy cannot be determined by our study because our samples are restricted to 5 cm above the esophagogastric junction.
Like others previously (16), we chose this location as a standardized approach for sampling the distal esophagus. Future studies
should compare ISD at different esophagus locations in patients
with GERD and FH.
Regarding the clinical applicability of our results, electron
microscopy is not widely available outside academic institutions.
However, if ISD is confirmed as a useful marker of GERD, it can
be used as a gold standard in future studies examining newer,
more user-friendly, and widely available diagnostic modalities;
for instance, new endoscopic imaging modalities such as confocal
endomicroscopy or narrow band imaging with magnification.
In conclusion, this prospective, blinded study showed increased
ISD in refractory heartburn patients with underlying GERD but
© 2011 by the American College of Gastroenterology
not in those with FH. Our findings suggest that measurement of
ISD by TEM might be a useful tool to distinguish GERD from FH
in patients with refractory heartburn.
CONFLICT OF INTEREST
Guarantor of the article: Marcelo F. Vela, MD, MSCR.
Specific author contributions: Marcelo F. Vela: study concept,
design and supervision, data analysis, drafting of manuscript, had
access to the data and made the decision to publish the findings;
Brandon M. Craft: analysis of electron micrographs; Neeraj Sharma:
analysis of impedance–pH data; Janice Freeman: acquisition and
analysis of impedance–pH data; Debra Hazen-Martin: electron
microscopy analysis of esophageal biopsies.
Financial Support: Dr Vela: American College of Gastroenterology
Junior Faculty Development Award; American Gastroenterological Association June and Don Castell Award in Esophageal Clinical
Research Award.
Potential competing interests: Dr Vela: Speakers bureau: Sandhill
Scientific, Given Imaging/Sierra Scientific, and Takeda. Advisory
board: AstraZeneca and Given Imaging/Sierra Scientific. All other
authors declare no conflict of interest.
Study Highlights
WHAT IS CURRENT KNOWLEDGE
3The persistence of heartburn despite pharmacological acid
suppression may be explained by ongoing gastroesophageal
reflux disease (GERD) or functional heartburn (FH).
3In patients with refractory heartburn, distinguishing GERD from
FH is important as the management approach is different.
3Dilation of the intercellular space diameter (ISD) in
esophageal epithelium, measured by transmission
electron microscopy, is a morphological marker of GERD
present in both erosive and nonerosive reflux disease.
WHAT IS NEW HERE
3ISD is higher in GERD compared with FH and healthy
controls; ISD is similar in FH and controls.
3Measurement of ISD by transmission electron microscopy
might be a useful method to distinguish GERD from FH in
patients with refractory heartburn.
3As a tool to discriminate GERD from FH, ISD measurements
could potentially be used to guide therapy: additional reflux
control for GERD, and non-GERD treatments for FH (e.g.,
visceral analgesia).
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