Perception of gastro-oesophageal reflux

Recent insights on functional heartburn and reflux hypersensitivity

PURPOSE OF REVIEW

Rome IV experts have proposed that gastroesophageal reflux disease (GERD) should be diagnosed only in patients with abnormal esophageal acid exposure, and that reflux hypersensitivity (RH) and functional heartburn (FH) both should be considered functional conditions separate from GERD. Although past and recent evidence support that FH can be completely distinguished from GERD, the concept that RH is not GERD is highly questionable. This review attempts to provide current data on these issues.

RECENT FINDINGS

Many recent investigations have provided new data on the different pathophysiological features characterizing RH and FH. Major differences have emerged from analyses of impedance-pH monitoring studies using the novel impedance metrics of baseline impedance (an index of mucosal integrity) and the rate of postreflux swallow-induced peristaltic waves (a reflection of the integrity of esophageal chemical clearance).

SUMMARY

The better ability to interpret impedance-pH tracings together with earlier data on the different prevalence of microscopic esophagitis in RH and FH patients, and recent studies documenting poor therapeutic efficacy of pain modulators and good results of antireflux surgery for RH support recategorization of RH within the GERD world. Further research is needed to correctly phenotype patients who have heartburn without mucosal breaks, and to guide their effective management.

Phenotypes of Gastroesophageal Reflux Disease: Where Rome, Lyon, and Montreal Meet

Gastroesophageal reflux disease (GERD) is now one of the most common diagnoses made in a gastroenterology practice. From a conventional pathophysiological perspective, GERD is conceptualized as incompetence of the antireflux barrier at the esophagogastric junction; the more severe that incompetence, the worse the disease. However, it is increasingly clear that many presentations of GERD represent distinct phenotypes with unique predisposing cofactors and pathophysiology outside of this paradigm. Three major consensus initiatives have grappled with this dilemma (the Montreal Consensus, The Rome Foundation, and the Lyon Consensus), each from a different perspective. Montreal struggled to define the disease, Rome sought to characterize its functional attributes, while Lyon examined its physiological attributes. Here, we merge the 3 perspectives, developing the concept that what has come to be known as GERD is actually a family of syndromes with a complex matrix of contributing pathophysiology. A corollary to this is that the concept of one size fits all to therapeutics does not apply, and that although escalating treatment with proton pump inhibitors (PPIs) may be pertinent to healing esophagitis, its applicability beyond that is highly questionable. Similarly, failing to recognize the modulating effects of anxiety, hypervigilance, and visceral and central hypersensitivity on symptom severity has greatly oversimplified the problem. That oversimplification has led to excessive use of PPIs for everything captured under the GERD umbrella and shown a broad spectrum of syndromes less amenable to PPI therapy in any dose. It is with this in mind that we delineate this precision medicine concept of GERD.

Interplay of spinal and vagal pathways on esophageal acid-related anterior cingulate cortex functional networks in rats

Esophageal acid sensory signals are transmitted by both vagal and spinal pathways to the cerebral cortex. The influence and interplay of these pathways on esophageal acid-related functional connectivity has been elusive. Our aim was to evaluate the esophageal acid exposure-related effect on the anterior cingulate cortex (ACC) functional connectivity networks using functional MRI-guided functional connectivity MRI (fcMRI) analysis. We studied six Sprague-Dawley rats for fcMRI experiments under dexmedetomidine hydrochloride anesthesia. Each rat was scanned for 6 min before and after esophageal hydrochloric acid infusion (0.1 N, 0.2 ml/min). The protocol was repeated before and after bilateral cervical vagotomy on the same rat. Seed-based fcMRI analysis was used to examine ACC networks and acid-induced network alterations. Three-factor repeated-measures ANOVA analysis among all four subgroups revealed that the interaction of acid infusion and bilateral vagotomy was mainly detected in the hypothalamus, insula, left secondary somatosensory cortex, left parietal cortex, and right thalamus in the left ACC network. In the right ACC network, this interaction effect was detected in the caudate putamen, insula, motor, primary somatosensory cortex, secondary somatosensory cortex, and thalamic regions. These regions in the ACC networks showed decreased intranetwork connectivity due to acid infusion. However, after bilateral vagotomy, intranetwork connectivity strength inversed and became stronger following postvagotomy acid infusion. Signals transmitted through both the vagal nerve and spinal nerves play a role in esophageal acid-related functional connectivity of the ACC. The vagal signals appear to dampen the acid sensation-related functional connectivity of the ACC networks. NEW & NOTEWORTHY These studies show that esophageal acid-induced brain functional connectivity changes are vagally mediated and suggest that signals transmitted through both the vagal nerve and spinal nerves play a role in esophageal acid-related functional connectivity of the anterior cingulate cortex. This paper focuses on the development of a novel rat functional MRI model fostering improved understanding of acid-related esophageal disorders.

Changes in symptom reflux association using dynamic pH thresholds during ambulatory pH monitoring: an observational cross-sectional study

Symptom reflux association (SRA) assesses symptoms associated with reflux events defined by pH <4.0, but limited symptoms associate with reflux events. We evaluated the impact of alternate pH thresholds on SRA in a large ambulatory pH database. Acid exposure time (AET), reflux events, and associated symptoms (within 2 minutes following a reflux event) were extracted from ambulatory pH studies performed off antireflux therapy (722 patients, 49.1 ± 0.5 years, 66.8% F) over a 7-year period. Symptom association probability (SAP) and symptom index (SI) were calculated at pH 3.5, 4.0, 4.5, and 5. Receiver operating characteristics (ROC) were generated using SRA at any pH as gold standard; areas under the curve (AUCs) were determined. Discordant cases were reanalyzed to determine changes in SRA and predictors of change using multivariate regression. At pH 4.0, 41% had a positive SAP, and 34% had a positive SI. While there was sustained gain in SI positivity from acidic to more weakly acidic pH thresholds, SAP positivity was highest at pH 4.5. On ROC analysis, performance characteristics were best at pH 4.0 (AUC 0.97) for SAP, and at pH 4.5 and 5.0 (AUC 0.92-0.94) for SI. On multivariate logistic regression adjusting for age, gender, and change in AET and reflux events, only number of associated symptoms predicted change in SRA (P < 0.0001). Changing pH thresholds for reflux events augments SRA by increasing reflux events associated with existing symptoms, while symptom recording remains the principal determinant of SRA.

Effect of nortriptyline on brain responses to painful esophageal acid infusion in patients with non-erosive reflux disease

BACKGROUND

Non-erosive reflux disease (NERD) patients generally present with heartburn as the main symptom. Antidepressants might help to relieve heartburn by acting on the esophagus-brain axis. We aimed to assess the effect of nortriptyline on behavioral and brain responses to painful esophageal acid infusion in NERD patients evaluated with functional magnetic resonance imaging (fMRI).

METHODS

In a randomized double-blind crossover design, 20 NERD patients off proton pump inhibitors (36.1 ± 9.3 years, 75% women) were assigned to 21 days of nortriptyline and placebo, in counterbalanced order, with a 21 days washout period in between both treatment periods. Changes in acid-induced brain response on fMRI and heartburn perception were assessed and at the end of each treatment.

KEY RESULTS

Nortriptyline significantly reduced the acid-induced brain response in prefrontal cortex (median [IQR]: -1.9 [-4.5 to -0.1] vs -0.3 [-2.5 to 2.3]; p = 0.050), caudate (-3.0 [-5.1 to -0.01] vs 0.48 [-1.9 to 3.1]; p = 0.029), insula (-2.4 [-4.8 to -0.6] vs -0.2 [-1.5 to 1.5]; p = 0.029), cingulate (-4.2 [-8.8 to -0.1] vs -0.6 [-1.8 to 3.0]; p = 0.017), and hippocampus (-2.7 [-6.0 to 0.5] vs -0.04 [-2.3 to 1.9]; p = 0.006) in comparison with placebo. However, there was no significant difference between nortriptyline and placebo in clinical outcomes and side effects.

CONCLUSIONS & INFERENCES

Nortriptyline decreased the brain response to esophageal acid infusion more markedly than placebo, but without clinical significance.

Current pharmacological management of gastroesophageal reflux disease

Gastroesophageal reflux disease (GERD), a common disorder with troublesome symptoms caused by reflux of gastric contents into the esophagus, has adverse impact on quality of life. A variety of medications have been used in GERD treatment, and acid suppression therapy is the mainstay of treatment for GERD. Although proton pump inhibitor is the most potent acid suppressant and provides good efficacy in esophagitis healing and symptom relief, about one-third of patients with GERD still have persistent symptoms with poor response to standard dose PPI. Antacids, alginate, histamine type-2 receptor antagonists, and prokinetic agents are usually used as add-on therapy to PPI in clinical practice. Development of novel therapeutic agents has focused on the underlying mechanisms of GERD, such as transient lower esophageal sphincter relaxation, motility disorder, mucosal protection, and esophageal hypersensitivity. Newer formulations of PPI with faster and longer duration of action and potassium-competitive acid blocker, a newer acid suppressant, have also been investigated in clinical trials. In this review, we summarize the current and developing therapeutic agents for GERD treatment.

NERD: an umbrella term including heterogeneous subpopulations

Nonerosive reflux disease (NERD) represents the more common phenotypic presentation of GERD and comprises patients who have typical symptoms without any mucosal breaks at endoscopy. However, these patients are markedly heterogeneous from a pathophysiological point of view and should be correctly classified by means of 24 h impedance-pH testing, which enables detection of both acidic and weakly acidic reflux and correlation with symptoms. This technique is able to identify two subsets of NERD (that is, patients with an excess of acid or with a hypersensitive oesophagus to both acid and weakly acidic reflux) and patients with functional heartburn (who do not have any kind of reflux underlying their symptoms and must be excluded from the realm of GERD). The mechanisms of symptom generation are not clear in patients with NERD, but the presence of microscopic oesophagitis, including the dilation of intercellular spaces, seems to have a relevant role. Patients with NERD in whom acid is the main pathogenetic factor respond successfully to PPI therapy, while those with hypersensitive oesophagus to weakly acidic reflux need to be treated with reflux inhibitors or surgery, although the experience in this field is very scant. Patients with functional heartburn should undergo therapy with pain modulators, but large placebo-controlled trials are necessary.

Peripheral and central nervous contribution to gastrointestinal symptoms in diabetic patients with autonomic neuropathy

BACKGROUND & AIMS

Long-term diabetes mellitus (DM) has been associated with neuronal changes in the enteric, peripheral and/or central nervous system. Moreover, abnormal visceral sensation and gastrointestinal (GI) symptoms are seen in up to 75% of patients. To explore the role of diabetic autonomic neuropathy (DAN) in patients with long-standing DM, we investigated psychophysical responses and neuronal activity recorded as evoked brain potentials and dipolar source modelling.

METHODS

Fifteen healthy volunteers and 14 type-1 DM patients with DAN were assessed with a symptom score index characterizing upper GI abnormalities. Multichannel (62) electroencephalography was recorded during painful electrical stimulation of the lower oesophagus. Brain activity to painful stimulations was modelled using Brain Electrical Source Analysis (besa).

RESULTS

Diabetic patients had higher stimulus intensities to evoke painful sensation (p ≤ 0.001), longer latencies of N2 and P2 components (both p ≤ 0.001), and lower amplitudes of P1-N2 and N2-P2 complexes (p ≤ 0.001; p = 0.02). Inverse modelling of brain sources showed deeper bilateral insular dipolar source localization (p = 0.002). Symptom score index was negatively correlated with the depth of insular activity (p = 0.004) and positively correlated with insular dipole strength (p = 0.03).

CONCLUSION

DM patients show peripheral and central neuroplastic changes. Moreover, the role of abnormal insular processing may explain the appearance and persistence of GI symptoms related to DAN. This enhanced understanding of DAN may have future clinical and therapeutical implications.