Automated calculation of the distal contractile integral in esophageal pressure topography with a region-growing algorithm

Background The distal contractile integral (DCI) is an index of contractile vigor in high‐resolution esophageal pressure topography (EPT) calculated as the product of amplitude, duration, and span of the distal esophageal contraction. The aim of this study was to develop an automated algorithm calculating DCI. Methods The DCI was calculated conventionally using ManoView? (Given Imaging, Los Angeles, CA, USA) software in EPT studies from 72 controls and 20 patients and compared to the calculation using a MATLAB? (Version 7.9.0, R2009b; The MathWorks Inc., Natick, MA, USA) ‘region‐growing’ algorithm. This algorithm first established the spatial limits of the distal contraction (the proximal pressure trough to either the distal pressure trough or to the superior margin of the lower esophageal sphincter at rest). Pixel‐by‐pixel horizontal line segments were then analyzed within this span starting at the pressure maximum and extending outward from that point. The limits of ‘region‐growing’ were defined either by the spatial DCI limits or by encountering a pressure <20 mmHg. The DCI was then calculated as the total units of mmHg s cm greater than 20 mmHg within this domain. Key Results Excellent correlation existed between the two methods (r = 0.98, P < 0.001). The DCI values obtained with the conventional calculation were slightly but significantly greater than with the region‐growing algorithm. Differences were attributed to the inclusion of vascular pressures in the conventional calculation or to differences in localization of the distal limit of the DCI. Conclusions & Inferences The proposed region‐growing algorithm provides an automated method to calculate DCI that limits inclusion of vascular pressure artifacts and minimizes the need for user input in data analysis.     

The contractile deceleration point: an important physiologic landmark on oesophageal pressure topography

Background This study aimed to correlate oesophageal bolus transit with features of oesophageal pressure topography (OPT) plots and establish OPT metrics for accurately measuring peristaltic velocity. Methods About 18 subjects underwent concurrent OPT and fluoroscopy studies. The deglutitive Contractile Front Velocity (CFV) in OPT plots was subdivided into an initial fast phase (CFV_fast) and subsequent slow phase (CFV_slow) separated by a user‐defined deceleration point (CDP). Fluoroscopy studies were analyzed for the transition from the initial rapidly propagated luminal closure associated with peristalsis to slow bolus clearance characteristic of phrenic ampullary emptying and to identify the pressure sensors at the closure front and at the hiatus. Oesophageal pressure topography measures were correlated with fluoroscopic milestones of bolus transit. Oesophageal pressure topography studies from another 68 volunteers were utilized to develop normative ranges for CFV_fast and CFV_slow. Key Results A distinct change in velocity could be determined in all 36 barium swallows with the fast and slow contractile segments having a median velocity of 4.2 cm s^?1 and 1.0 cm s^?1, respectively. The CDP noted on OPT correlated closely with formation of the phrenic ampulla making CFV_fast (mean 5.1 cm s^?1) correspond closely to peristaltic propagation and CFV_slow (mean 1.7 cm s^?1) to ampullary emptying. Conclusions & Inferences The deceleration point in the CFV on OPT plots accurately demarcated the early region in which the CFV reflects peristaltic velocity (CFV_fast) from the later region where it reflects the progression of ampullary emptying (CFV_slow). These distinctions should help objectify definitions of disordered peristalsis, especially spasm, and improve understanding of impaired bolus transit across the oesophagogastric junction.     

Refining the criterion for an abnormal Integrated Relaxation Pressure in esophageal pressure topography based on the pattern of esophageal contractility using a classification and regression tree model

Background The Integrated Relaxation Pressure (IRP) is the esophageal pressure topography (EPT) metric used for assessing the adequacy of esophagogastric junction (EGJ) relaxation in the Chicago Classification of motility disorders. However, because the IRP value is also influenced by distal esophageal contractility, we hypothesized that its normal limits should vary with different patterns of contractility. Methods Five hundred and twenty two selected EPT studies were used to compare the accuracy of alternative analysis paradigms to that of a motility expert (the ‘gold standard’). Chicago Classification metrics were scored manually and used as inputs for MATLAB? programs that utilized either strict algorithm‐based interpretation (fixed abnormal IRP threshold of 15 mmHg) or a classification and regression tree (CART) model that selected variable IRP thresholds depending on the associated esophageal contractility. Key Results The sensitivity of the CART model for achalasia (93%) was better than that of the algorithm‐based approach (85%) on account of using variable IRP thresholds that ranged from a low value of >10 mmHg to distinguish type I achalasia from absent peristalsis to a high value of >17 mmHg to distinguish type III achalasia from distal esophageal spasm. Additionally, type II achalasia was diagnosed solely by panesophageal pressurization without the IRP entering the algorithm. Conclusions & Inferences Automated interpretation of EPT studies more closely mimics that of a motility expert when IRP thresholds for impaired EGJ relaxation are adjusted depending on the pattern of associated esophageal contractility. The range of IRP cutoffs suggested by the CART model ranged from 10 to 17 mmHg.     

Manometric features of eosinophilic esophagitis in esophageal pressure topography

Background Although most of the patients with eosinophilic esophagitis (EoE) have mucosal and structural changes that could potentially explain their symptoms, it is unclear whether EoE is associated with abnormal esophageal motor function. The aims of this study were to evaluate the esophageal pressure topography (EPT) findings in EoE and to compare them with controls and patients with gastro‐esophageal disease (GERD). Methods Esophageal pressure topography studies in 48 EoE patients, 48 GERD patients, and 50 controls were compared. The esophageal contractile pattern was described for ten 5‐mL swallows for each subject and each swallow was secondarily characterized based on the bolus pressurization pattern: absent, pan‐esophageal pressurization, or compartmentalized distal pressurization. Key Results Thirty‐seven percent of EoE patients were classified as having abnormal esophageal motility. The most frequent diagnoses were of weak peristalsis and frequent failed peristalsis. Although motility disorders were more frequent in EoE patients than in controls, the prevalence and type were similar to those observed in GERD patients (P = 0.61, chi‐square test). Pan‐esophageal pressurization was present in 17% of EoE and 2% of GERD patients while compartmentalized pressurization was present in 19% of EoE and 10% of GERD patients. These patterns were not seen in control subjects. Conclusions & Inferences The prevalence of abnormal esophageal motility in EoE was approximately 37% and was similar in frequency and type to motor patterns observed in GERD. Eosinophilic esophagitis patients were more likely to have abnormal bolus pressurization patterns during swallowing and we hypothesize that this may be a manifestation of reduced esophageal compliance.     

High‐resolution esophageal pressure topography is superior to conventional sleeve manometry for the detection of transient lower esophageal sphincter relaxations associated with a reflux event

Background Transient lower esophageal sphincter relaxations (TLESRs) are the main mechanism underlying gastro‐esophageal reflux and are detected during manometric studies using well defined criteria. Recently, high‐resolution esophageal pressure topography (HREPT) has been introduced and is now considered as the new standard to study esophageal and lower esophageal sphincter (LES) function. In this study we performed a head‐to‐head comparison between HREPT and conventional sleeve manometry for the detection of TLESRs. Methods A setup with two synchronized MMS‐solar systems was used. A solid state HREPT catheter, a water‐perfused sleeve catheter, and a multi intraluminal impedance pH (MII‐pH) catheter were introduced in 10 healthy volunteers (M6F4, age 19–56). Subjects were studied 0.5 h before and 3 h after ingestion of a standardized meal. Tracings were blinded and analyzed by the three authors according to the TLESR criteria. Key Results In the HREPT mode 156 TLESRs were scored, vs 143 during sleeve manometry (P = 0.10). Hundred and twenty‐three TLESRs were scored by both techniques. Of all TLESRs (177), 138 were associated with reflux (78%). High‐resolution esophageal pressure topography detected significantly more TLESRs associated with a reflux event (132 vs 119, P = 0.015) resulting in a sensitivity for detection of TLESRs with reflux of 96% compared to 86% respectively. Analysis of the discordant TLESRs associated with reflux showed that TLESRs were missed by sleeve manometry due to low basal LES pressure (N = 5), unstable pharyngeal signal (N = 4), and residual sleeve pressure >2 mmHg (N = 10). Conclusions & Inferences The HREPT is superior to sleeve manometry for the detection of TLESRs associated with reflux. However, rigid HREPT criteria are awaited.     

Physiology of diffuse esophageal spasm (DES) – when normal swallows are not normal

Background Diffuse esophageal spasm (DES) is characterized on manometry by a combination of simultaneous contractions and normal swallows. The aim of this study was to examine the manometric characteristics of simultaneous and ‘normal’ swallows in patients with DES patients compared with normal controls. Methods Manometric studies from 69 patients with DES and 20 controls were analysed to determine the proportion of normal, hypertensive, ineffective and simultaneous contractions, and the velocity of propagation along the esophagus, the duration and amplitude of contraction and the relaxation characteristics (nadir and duration) of the lower esophageal sphincter. Key Results The propagation velocity was the only significant difference between normal swallows and simultaneous contractions in DES patients (middle third: 49.2 VS 101.2 mm s⁻¹, P ≤ 0.001 lower third: 44.1 VS 88.7 mm s⁻¹, P ≤ 0.001). ‘Normal’ swallows in patients with DES had a greater velocity of propagation than those in age‐matched control subjects (middle third: 49.2 VS 37.0 mm s⁻¹, P = 0.02, lower third: 44.1 VS 23.3 mm s⁻¹, P ≤ 0.001). Conclusions & Inferences As expected, simultaneous contractions of DES patients differ from ‘normal’ swallows in DES patients mainly regarding the velocity of propagation of contraction but are similar in amplitude, however ‘normal’ swallows of DES patients are also more rapidly propagated along the esophagus than normal swallows of a control group suggesting that all swallows in DES are affected to some degree by the same process.     

Normative values and inter‐observer agreement for liquid and solid bolus swallows in upright and supine positions as assessed by esophageal high‐resolution manometry

Background High‐resolution manometry (HRM) with spatiotemporal representation of pressure data is a recent advance in esophageal measurement. At present, normal values are available for 5 mL water swallows in the supine position. This study provides reference values for liquid and solid bolus swallows in the upright seated and supine positions. Methods A total of 23 asymptomatic volunteers (11M : 12F, age 20–56) underwent HRM (Manoscan 360; Sierra Scientific Instruments) with 5 mL water and 1 cm³ bread swallows in the upright and supine positions. Normal values for primary parameters associated with effective bolus transport [proximal transition zone length (PTZ, assesses peristaltic coordination], contraction front velocity (CFV), distal contractile index (DCI) and integrated relaxation pressure (IRP)] are presented. For each parameter, median values along with the 5–95th percentile range are reported. Inter‐observer agreement between independent observers is reported using the intra‐class correlation coefficient. Key Results A higher proportion of swallows were peristaltic for liquids than solids in both the upright and supine positions (both P < 0.05). As workload increases with solid bolus and on moving from the upright to the supine position the esophageal contractile response resulted in a shorter PTZ, a slower CFV, and a more vigorous DCI. Also IRP increased during solid bolus transit (all P < 0.01). There was significant agreement between independent observers for HRM parameters. Conclusions & Inferences Normative values for esophageal function for solids as well as liquids and in the ‘physiologic’, upright position will optimize the utility of HRM studies. The high level of inter‐observer agreement indicates that these can be applied as reference values in clinical practice.