Effect of esophageal contraction on esophageal wall blood perfusion

Necrotizing Esophagitis: A Big Squeeze?

Necrotizing esophagitis is rare and poorly understood. The etiologies reported in what little has been published (i.e., gastroesophageal reflux exacerbated by gastric outlet obstruction and low-flow ischemia) seem somewhat simplistic and lack any direct evidence. The following paper illustrates a recent clinical case while laying out arguments supporting esophageal spasm as a possible contributing factor.

The Mexican consensus on non-cardiac chest pain

INTRODUCTION

Non-cardiac chest pain is defined as a clinical syndrome characterized by retrosternal pain similar to that of angina pectoris, but of non-cardiac origin and produced by esophageal, musculoskeletal, pulmonary, or psychiatric diseases.

AIM

To present a consensus review based on evidence regarding the definition, epidemiology, pathophysiology, and diagnosis of non-cardiac chest pain, as well as the therapeutic options for those patients.

METHODS

Three general coordinators carried out a literature review of all articles published in English and Spanish on the theme and formulated 38 initial statements, dividing them into 3 main categories: (i)definitions, epidemiology, and pathophysiology; (ii)diagnosis, and (iii)treatment. The statements underwent 3rounds of voting, utilizing the Delphi system. The final statements were those that reached >75% agreement, and they were rated utilizing the GRADE system.

RESULTS AND CONCLUSIONS

The final consensus included 29 statements. All patients presenting with chest pain should initially be evaluated by a cardiologist. The most common cause of non-cardiac chest pain is gastroesophageal reflux disease. If there are no alarm symptoms, the initial approach should be a therapeutic trial with a proton pump inhibitor for 2-4weeks. If dysphagia or alarm symptoms are present, endoscopy is recommended. High-resolution manometry is the best method for ruling out spastic motor disorders and achalasia and pH monitoring aids in demonstrating abnormal esophageal acid exposure. Treatment should be directed at the pathophysiologic mechanism. It can include proton pump inhibitors, neuromodulators and/or smooth muscle relaxants, psychologic intervention and/or cognitive therapy, and occasionally surgery or endoscopic therapy.

Catheter-based high-frequency intraluminal ultrasound imaging is a powerful tool to study esophageal dysmotility patients

High-resolution manometry (HRM) is currently the most important diagnostic test for esophageal motility disorders, providing information on the contraction pattern of the circular muscle layer, which helps classify these esophageal motor diseases. However, with the increasing development of ultrasound, other techniques, such as high-frequency intraluminal ultrasound (HFIUS), have gained importance. This technique uses a flexible shaft with a central wire integrated into a standard endoscope, which facilitates real-time sonography. Its main utility is to provide anatomical information on the structure of the esophageal wall, including both the circular and longitudinal layers that constitute the esophageal muscularis propria. Increasing knowledge about these motility disorders has led to the hypothesis that, in addition to an abnormal contraction pattern of the circular muscle, an overall increased muscle thickness and an abnormal longitudinal muscle contraction could be added as pathophysiological factors. The increase in muscle thickness could be an important indicator of the severity of diseases, such as achalasia, distal esophageal spasm, or hypercontractile esophagus. More studies are required before definitive conclusions can be reached, but HFIUS employed simultaneously with HRM could provide a more complete and precise evaluation of these esophageal motor disorders.

Temporal and spectral properties of esophageal mucosal blood perfusion: a comparison between normal subjects and nutcracker esophagus patients

BACKGROUND

The mechanism of esophageal pain in patients with nutcracker esophagus (NE) and other esophageal motor disorders is not known. Our recent study shows that baseline esophageal mucosal perfusion, measured by laser Doppler perfusion monitoring, is lower in NE patients compared to controls. The goal of our current study was to perform a more detailed analysis of esophageal mucosal blood perfusion (EMBP) waveform of NE patients and controls to determine the optimal EMBP biomarkers that combined with suitable statistical learning models produce robust discrimination between the two groups.

METHODS

Laser Doppler recordings of 10 normal subjects (mean age 43 ± 15 years, 8 males) and 10 patients (mean age 47 ± 5.5 years., 8 males) with NE were analyzed. Time and frequency domain features were extracted from the first twenty-minute recordings of the EMBP waveforms, statistically ranked according to four independent evaluation criterions, and analyzed using two statistical learning models, namely, logistic regression (LR) and support vector machines (SVM).

KEY RESULTS

The top three ranked predictors between the two groups were the 0.5 and 0.75 perfusion quantile values followed by the surface of the EMBP power spectrum in the frequency domain. ROC curve ranking produced a cross-validated AUC (area under the curve) of 0.93 for SVM and 0.90 for LR.

CONCLUSIONS & INFERENCES

We show that as a group NE patients have lower perfusion values compared to controls, however, there is an overlap between the two groups, suggesting that not all NE patients suffer from low mucosal perfusion levels.

Regulation and dysregulation of esophageal peristalsis by the integrated function of circular and longitudinal muscle layers in health and disease

Muscularis propria throughout the entire gastrointestinal tract including the esophagus is comprised of circular and longitudinal muscle layers. Based on the studies conducted in the colon and the small intestine, for more than a century, it has been debated whether the two muscle layers contract synchronously or reciprocally during the ascending contraction and descending relaxation of the peristaltic reflex. Recent studies in the esophagus and colon prove that the two muscle layers indeed contract and relax together in almost perfect synchrony during ascending contraction and descending relaxation of the peristaltic reflex, respectively. Studies in patients with various types of esophageal motor disorders reveal temporal disassociation between the circular and longitudinal muscle layers. We suggest that the discoordination between the two muscle layers plays a role in the genesis of esophageal symptoms, i.e., dysphagia and esophageal pain. Certain pathologies may selectively target one and not the other muscle layer, e.g., in eosinophilic esophagitis there is a selective dysfunction of the longitudinal muscle layer. In achalasia esophagus, swallows are accompanied by the strong contraction of the longitudinal muscle without circular muscle contraction. The possibility that the discoordination between two muscle layers plays a role in the genesis of esophageal symptoms, i.e., dysphagia and esophageal pain are discussed. The purpose of this review is to summarize the regulation and dysregulation of peristalsis by the coordinated and discoordinated function of circular and longitudinal muscle layers in health and diseased states.

Low esophageal mucosal blood flow in patients with nutcracker esophagus

Nutcracker esophagus (NE) is characterized by high-amplitude peristaltic esophageal contractions, and these patients often present with symptoms of "angina-like" or noncardiac chest pain. Tissue ischemia is a known cause of visceral pain, and the goal of our present study was to determine whether esophageal wall blood perfusion (EWBP) is reduced in patients with NE. Fourteen normal subjects (mean age 51 yr, 11 men) and 12 patients (mean age 53 yr, 9 men) with NE and noncardiac chest pain were investigated. The EWBP was measured continuously using a custom-designed laser Doppler probe tethered to a Bravo capsule, which anchored it to the esophageal wall. The baseline EWBP in normal subjects was 651 ± 27 perfusion units. In patients with NE, the baseline EWBP was significantly lower than in the normal subjects (451 ± 32 perfusion units). The EWBP decreased after injection of edrophonium (which increases muscle contractions) and increased following sublingual nitroglycerin administration (which relaxes muscle) in normal subjects, as well as in NE patients. Spontaneous pain events during the recording period were often associated with drops in the EWBP. We propose that low EWBP leads to hypoxia of the esophageal tissue, which may be a mechanism of esophageal pain in patients with NE.

Pathophysiology of gastroesophageal reflux disease: new understanding in a new era

BACKGROUND

The prevalence of gastroesophageal reflux disease (GERD) has increased in the last decades and it is now one of the most common chronic diseases. Throughout time our insight in the pathophysiology of GERD has been characterized by remarkable back and forth swings, often prompted by new investigational techniques. Even today, the pathophysiology of GERD is not fully understood but it is now recognized to be a multifactorial disease. Among the factors that have been shown to be involved in the provocation or increase of reflux, are sliding hiatus hernia, low lower esophageal sphincter pressure, transient lower esophageal sphincter relaxation, the acid pocket, obesity, increased distensibility of the esophagogastric junction, prolonged esophageal clearance, and delayed gastric emptying. Moreover, multiple mechanisms influence the perception of GERD symptoms, such as the acidity of the refluxate, its proximal extent, the presence of gas in the refluxate, duodenogastroesophageal reflux, longitudinal muscle contraction, mucosal integrity, and peripheral and central sensitization. Understanding the pathophysiology of GERD is important for future targets for therapy as proton pump inhibitor-refractory GERD symptoms remain a common problem.

PURPOSE

In this review we provide an overview of the mechanisms leading to reflux and the factors influencing perception, in the light of historical developments. It is clear that further research remains necessary despite the recent advances in the understanding of the pathophysiology of GERD.

Esophageal function testing: beyond manometry and impedance

Manometry and impedance provide only surrogate information regarding longitudinal wall function and are focused on contractile amplitude and lumen content. Ultrasound imaging provides a unique perspective of esophageal function by providing important information regarding longitudinal muscle contraction. Laser Doppler assessment of perfusion may be an important complementary tool to assess abnormal wall blood perfusion as a possible mechanism of pain.

Distal esophageal spasm: an update

Distal esophageal spasm (DES) is an esophageal motility disorder that presents clinically with chest pain and/or dysphagia and is defined manometrically as simultaneous contractions in the distal (smooth muscle) esophagus in ≥20% of wet swallows (and amplitude contraction of ≥30 mmHg) alternating with normal peristalsis. With the introduction of high resolution esophageal pressure topography (EPT) in 2000, the definition of DES was modified. The Chicago classification proposed that the defining criteria for DES using EPT should be the presence of at least two premature contractions (distal latency<4.5 s) in a context of normal EGJ relaxation. The etiology of DES remains insufficiently understood, but evidence links nitric oxide (NO) deficiency as a culprit resulting in a disordered neural inhibition. GERD frequently coexists in DES, and its role in the pathogenesis of symptoms needs further evaluation. There is some evidence from small series that DES can progress to achalasia. Treatment remains challenging due in part to lack of randomized placebo-controlled trials. Current treatment agents include nitrates (both short and long acting), calcium-channel blockers, anticholinergic agents, 5-phosphodiesterase inhibitors, visceral analgesics (tricyclic agents or SSRI), and esophageal dilation. Acid suppression therapy is frequently used, but clinical outcome trials to support this approach are not available. Injection of botulinum toxin in the distal esophagus may be effective, but further data regarding the development of post-injection gastroesophageal reflux need to be assessed. Heller myotomy combined with fundoplication remains an alternative for the rare refractory patient. Preliminary studies suggest that the newly developed endoscopic technique of per oral endoscopic myotomy (POEM) may also be an alternative treatment modality.

Longitudinal muscle of the esophagus: its role in esophageal health and disease

PURPOSE OF REVIEW

The muscularis propria of the esophagus is organized into circular and longitudinal muscle layers. The function of the longitudinal muscle and its role in bolus propulsion are not clear. The goal of this review is to summarize what is known of the role of the longitudinal muscle in health, as well as in sensory and motor disorders of the esophagus.

RECENT FINDINGS

Simultaneous manometry and ultrasound imaging reveal that, during peristalsis, the two muscle layers of the esophagus contract in perfect synchrony. On the contrary, during transient lower esophageal sphincter (LES) relaxation, longitudinal muscle contracts independent of the circular muscle. Recent studies have provided novel insights into the role of the longitudinal muscle in LES relaxation and descending relaxation of the esophagus. In certain diseases (e.g. some motility disorders of the esophagus), there is discoordination between the two muscle layers, which likely plays an important role in the genesis of dysphagia and delayed esophageal emptying. There is close temporal correlation between prolonged contractions of the longitudinal muscles of the esophagus and esophageal 'angina-like' pain. Novel techniques to record longitudinal muscle contraction are reviewed.

SUMMARY

Longitudinal muscles of the esophagus play a key role in the physiology and pathophysiology of esophageal sensory and motor function. Neuro-pharmacologic controls of circular and longitudinal muscle are different, which provides an opportunity for the development of novel pharmacological therapies in the treatment of esophageal sensory and motor disorders.

How reflux causes symptoms: reflux perception in gastroesophageal reflux disease

In gastroesophageal reflux disease (GERD) symptoms arise due to reflux of gastric content into the oesophagus. However, the relation between magnitude and onset of reflux and symptom generation in GERD patients is far from simple; gastroesophageal reflux occurs several times a day in everyone and the majority of reflux episodes remains asymptomatic. This review aims to address the question how reflux causes symptoms, focussing on factors leading to enhanced reflux perception. We will highlight esophageal sensitivity variance between subtypes of GERD, which is influenced by peripheral sensitization of primary afferents, central sensitization of spinal dorsal horn neurons, impaired mucosal barrier function and genetic factors. We will also discuss the contribution of specific refluxate characteristics to reflux perception, including acidity, and the role of bile, pepsin and gas and proximal extent. Further understanding of reflux perception might improve GERD treatment, especially in current partial responders to therapy.

Longitudinal muscle dysfunction in achalasia esophagus and its relevance

Muscularis propria of the esophagus is organized into circular and longitudinal muscle layers. Goal of this review is to summarize the role of longitudinal muscle in physiology and pathophysiology of esophageal sensory and motor function. Simultaneous manometry and ultrasound imaging that measure circular and longitudinal muscle contraction respectively reveal that during peristalsis 2 layers of the esophagus contract in perfect synchrony. On the other hand, during transient relaxation of the lower esophageal sphincter (LES), longitudinal muscle contracts independently of circular muscle. Recent studies provide novel insights, i.e., longitudinal muscle contraction of the esophagus induces LES relaxation and possibly descending relaxation of the esophagus. In achalasia esophagus and other motility disorders there is discoordination between the 2 muscle layers. Longitudinal muscle contraction patterns are different in the recently described three types of achalasia identified by high-resolution manometry. Robust contraction of the longitudinal muscle in type II achalasia causes pan-esophageal pressurization and is the mechanism of whatever little esophageal emptying that take place in the absence of peristalsis and impaired LES relaxation. It may be that preserved longitudinal muscle contraction is also the reason for superior outcome to medical/surgical therapy in type II achalasia esophagus. Prolonged contractions of longitudinal muscles of the esophagus is a possible mechanism of heartburn and "angina like" pain seen in esophageal motility disorders and possibly achalasia esophagus. Novel techniques to record longitudinal muscle contraction are on the horizon. Neuro-pharmacologic control of circular and longitudinal muscles is different, which provides an important opportunity for the development of novel pharmacological therapies to treat sensory and motor disorders of the esophagus.

Esophageal wall blood perfusion during contraction and transient lower esophageal sphincter relaxation in humans

We recently reported that esophageal contraction reduces esophageal wall perfusion in an animal study. Our aim was to determine esophageal wall blood perfusion (EWBP) during esophageal contraction and transient lower esophageal sphincter relaxations (TLESRs) in humans. We studied 12 healthy volunteers. A custom-designed laser Doppler probe was anchored to the esophageal wall, 4-6 cm above the LES, by use of the Bravo pH system so that the laser light beam stay directed toward the esophageal mucosa. A high-resolution manometry equipped with impedance electrodes recorded esophageal pressures and reflux events. Synchronized pressure, impedance, pH, and EWBP recordings were obtained during dry and wet swallows and following a meal. Stable recordings of laser Doppler EWBP were only recorded when the laser Doppler probe was firmly anchored to the esophageal wall. Esophageal contractions induced by dry and wet swallows resulted in 46 ± 9% and 60 ± 10% reduction in the EWBP, respectively (compared to baseline). Reduction in EWBP was directly related to the amplitude (curvilinear fit) and duration of esophageal contraction. Atropine reduced the esophageal contraction amplitude and decreased the EWBP reduction associated with esophageal contraction. TLESRs were also associated with reduction in the EWBP, albeit of smaller amplitude (29 ± 3%) but longer duration (19 ± 2 s) compared with swallow-induced esophageal contractions. We report 1) an innovative technique to record EWBP for extended time periods in humans and 2) contraction of circular and longitudinal muscle during peristalsis and selective longitudinal muscle contraction during TLESR causes reduction in the EWBP; 3) using our innovative technique, future studies may determine whether esophageal wall ischemia is the cause of esophageal pain/heartburn.