May 13, 2016
The last decade has seen significant advances in the diagnosis and management of achalasia, a rare esophageal motility disorder resulting from impaired relaxation of the lower esophageal sphincter (LES) and loss of normal peristalsis. The primary symptoms — dysphagia and regurgitation — may be accompanied by weight loss, chest pain and heartburn.
The diagnosis is suspected based on these symptoms and confirmed by medical tests that have changed the way achalasia is diagnosed and treated, including high-resolution manometry (HRM), esophageal bolus transit assessment by intraluminal impedance and esophageal distensibility assessment with the EndoFLIP probe.
Manometry has evolved as a result of the introduction of high-resolution manometry catheters, the use of esophageal pressure topography (EPT) plots and the development of the Chicago Classification of esophageal motility disorders. Unlike conventional manometry, which relies on a limited number of sensors and displays pressure changes through line tracings, the HRM catheter has 36 closely spaced sensors that allow pressure recordings of both upper and lower esophageal sphincters along with the entire esophageal body in a spatial continuum, without the large gaps created by the conventional catheters.
EPT representations of the three achalasia subtypes
Three unique achalasia subtypes are now recognized in the Chicago Classification, each with a different response to available treatments.
To analyze and interpret the HRM studies, the manometric data is converted into esophageal pressure topography (EPT) plots — color-coded spatiotemporal representations of pressure readings in the esophagus. Based upon metrics derived from analysis of EPT plots, the Chicago Classification uses an algorithmic approach to diagnose esophageal motility disorders. Three unique achalasia subtypes are now recognized in the Chicago Classification, each with a different response to available treatments.
HRM has several advantages, says Marcelo F. Vela, M.D., a gastroenterologist at Mayo Clinic's campus in Arizona and a member of the international group in charge of development and updating of the Chicago Classification, as well as senior author of the most recent American College of Gastroenterology guidelines for achalasia.
"HRM provides a more reliable way to evaluate for achalasia — it has increased the sensitivity of manometry for detection of this motility disorder," he explains. "We used to have a problem with false-negatives with conventional catheters due to pseudorelaxation, a drop in LES pressure that creates the appearance of relaxation when there is esophageal shortening that elevates the LES and leaves this single sensor temporarily in the stomach.
"With EPT plots, we can trace the movements of the LES and adjust the measurements to avoid this issue. In addition to greater sensitivity, the Chicago Classification now allows us to diagnose three distinct manometric subtypes of achalasia, which have been shown to respond differently to treatment." The most recent iteration of the Chicago Classification (Chicago Classification v3.0), was published in Neurogastroenterology & Motility in 2015.
Another important development in HRM testing is the use of multiple rapid swallows to assess smooth muscle peristaltic reserve. "After completing ten single swallows, patients are asked to do a sequence of multiple rapid swallows. Based upon early data, it appears the response to this maneuver can help predict the development of dysphagia after fundoplication surgery — patients who are not able to augment the strength of contraction with multiple rapid swallows are more likely to have difficulty swallowing after anti-reflux surgery," Dr. Vela explains.
Insights into smooth muscle peristaltic reserve are also being applied to other fields; Dr. Vela and colleagues recently published results of a study using multiple rapid swallows to evaluate patients with systemic sclerosis. Their study is currently in press at Clinical Gastroenterology and Hepatology.
Multichannel esophageal impedance
Incorporating multiple impedance electrodes in high-resolution manometry catheters allows the assessment of bolus movement along the length of the esophagus, in both antegrade (swallowing) and retrograde (reflux) direction. A liquid swallow causes impedance to decrease sequentially from the proximal to the distal esophagus, whereas liquid esophageal reflux causes impedance drops that progress in a retrograde manner from distal to proximal esophagus.
During high-resolution esophageal impedance manometry, assessment of bolus transit through impedance complements the motility findings provided by high resolution manometry. In achalasia, preliminary studies show that multichannel esophageal impedance can be used to perform timed emptying of an esophageal bolus, an approach that could potentially replace the frequently used timed barium esophagogram, thus eliminating the need for radiation exposure while adding just five minutes to the manometry protocol.
A more recent and important advance is the development of the endoluminal functional lumen imaging probe (EndoFLIP), which uses impedance planimetry and a pressure sensor to measure the distensibility and cross-sectional area of hollow organs in real time. In achalasia patients, the EndoFLIP probe provides a dynamic assessment of distensibility of the esophagogastric junction (EGJ), which is valuable for evaluation and treatment.
Treated and untreated achalasia
In successfully treated achalasia, patients experience symptom relief with improved esophageal emptying.
"It's an important tool, both for diagnosis as well as during and after treatment," Dr. Vela says. "In patients in whom the diagnosis of achalasia is not clear by manometry, reduced distensibility of the EGJ appears to predict a good response to achalasia therapies. Furthermore, EGJ distensibility measurements performed during myotomy, either laparoscopic or endoscopic, can document whether distensibility has been appropriately increased by the treatment.
"We are now performing EndoFLIP routinely during peroral endoscopic myotomy (POEM) in our achalasia patients. In addition, for patients referred to us because of incomplete response to treatment or recurrence of symptoms after therapy, EndoFLIP measurements can help guide further interventions by identifying those in whom additional therapies to disrupt the EGJ are warranted."
HRM and EPT interpreted through the Chicago Classification, bolus transit assessment by impedance, and distensibility assessment by EndoFLIP are all very good examples of disruptive innovations in the realm of achalasia, he says. "The way we evaluate and treat patients has changed significantly over the last decade."
For more information
Kahrilas PJ, et al. The Chicago Classification of esophageal motility disorders, v3.0. Neurogastroenterology & Motility. 2015;27:160.
Carlson DA, et al. Loss of peristaltic reserve, determined by multiple rapid swallows is the most frequent esophageal motility abnormality in patients with systemic sclerosis. Clinical Gastroenterology and Hepatology. In press.