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After all test swallows are classified, an esophageal motility diagnosis can be generated according to the Chicago Classification, which provides a hierarchical framework (Figure 8.5) [4]. Because peristalsis may be altered in response to EGJ outflow obstruction, the presence or absence of an EGJ outflow obstruction (median IRP exceeding the upper limit of normal) is the initial branch point in the diagnostic classification scheme. If EGJ outflow obstruction is associated with 100% failed or premature (spastic) swallows, a diagnosis of achalasia is achieved. Achalasia is then subclassified as type I, II, or III (Figure 8.6), which has both prognostic and treatment implications. Type II (with panesophageal pressurization) has the greatest likelihood of treatment success, while type III (spastic) has the lowest treatment success rate (Table 8.2) [42–45]. With respect to therapy, myotomy – particularly a calibrated endoscopic myotomy – is the preferred initial therapeutic option in type III achalasia, whereas pneumatic dilation or myotomy may be equally effective with type I or II [43, 46].

In the circumstance that the IRP is abnormally high but the associated contractile pattern does not meet the criteria for achalasia, EGJ outflow obstruction is diagnosed. This diagnosis is clinically heterogeneous with a spectrum of potential diagnoses including evolving achalasia, subtle mechanical obstruction, extra‐luminal obstruction, hiatal hernia, opiate effect, and clinically insignificant recording artifact [15,47–51]. Hence, a cautionary approach to management and complementary testing is advised. This may involve adjunctive and provocative manometric maneuvers as well as non‐manometric tests such as a barium esophagram, cross‐sectional imaging, or functional luminal imaging probe testing. Emphasizing this point, two series published in the past few years found that many patients with EGJ outflow obstruction were minimally symptomatic or asymptomatic, that in 20–40% of cases the “disorder” resolved spontaneously, and that only 12–40% ended up being treated as achalasia [48, 52].

Figure 8.5 The Chicago Classification of esophageal motility diagnoses [4]. An esophageal motility diagnosis can be determined by a hierarchical classification scheme: (i) evaluate for esophagogastric junction (EGJ) outflow obstruction; (ii) evaluate esophageal contractile and pressurization patterns. Both “failed” and “weak” swallows are considered “ineffective” swallows. DCI, distal contractile integral. DL, distal latency. IRP, integrated relaxation pressure.

Source: Based on Kahrilas, Bredenoord, Fox, et al. [4].

Figure 8.6 Achalasia subtypes. All three subtypes are characterized by elevated integrated relaxation pressure. (A) Type I achalasia: absent contractility and no pressurization. (B) Type II achalasia: absent contractility and pan‐esophageal pressurization (*). (C) Type III achalasia: premature swallows; the distal latency (arrow) was 3.8 seconds.

Source: Used with permission from the Esophageal Center at Northwestern University. Data from Pandolfino, Kwiatek, and Nealis [42].

With a normal IRP, the percentage of premature, hypercontractile, and failed swallows can be applied to identify major disorders of peristalsis, which are patterns of contractility not observed in asymptomatic control subjects. Distal esophageal spasm (DES) is defined when ≥ 20% of swallows are premature [4, 39]. Hypercontractile (or jackhammer) esophagus is defined when ≥ 20% of swallows are hypercontractile but not premature [36]. Absent contractility is designated when 100% of swallows are failed. However, when absent contractility is observed, particularly if the median IRP is marginally normal (or if panesophageal pressurization is present), a diagnosis of achalasia should be strongly considered [4, 53, 54].

A minor disorder of peristalsis is established if the median IRP is normal, a major disorder of peristalsis is excluded, and either ≥ 50% of swallows are weak or failed (ineffective esophageal motility, IEM) or ≥ 50% of swallows have large peristaltic breaks (fragmented peristalsis). Both of these diagnoses are associated with impaired esophageal bolus clearance and can be seen in patients presenting with dysphagia or reflux symptoms. However, these diagnoses can also be observed in asymptomatic controls; thus the clinical relevance of minor disorders of peristalsis is variable [55].

Table 8.2 Summary of publications describing achalasia outcomes by HRM achalasia subtypes. PD, pneumatic dilation; LHM, laparoscopic Heller’s myotomy; Botox, botulinum toxin injection

Publication	N (treatment type)	Type I	Type II	Type III
Pandolfino 2008 [42]	99 (PD, LHM, Botox)	56% (n = 21)	96% (n = 49)	29% (n = 29)
Salvador 2010 [45]	246 (LHM)	85% (n = 96)	95% (n = 127)	69% (n = 23)
Pratap 2011 [44]	51 (PD)	63% (n = 24)	90% (n = 24)	33% (n = 3)
Rohof 2013 [43]	176 (RCT: PD, LHM)	86% (PD) 81% (LHM) (n = 44)	100% (PD) 95% (LHM) (n = 114)	40% (PD) 86% (LHM) (n = 18)

Finally, if no major motility disorder or minor disorder of peristalsis is diagnosed, a diagnosis of normal motility is reached. However, HRM is not a perfect test, and in the circumstance of a highly symptomatic patient, additional evaluation may remain warranted before pursuing an alternative management pathway directed at a functional gastrointestinal syndrome. Considerations may include complementary evaluation with adjunctive and provocative manometric maneuvers, or additional imaging (e.g. barium esophagram or a functional luminal imaging probe study).

More detailed discussion of specific esophageal motility disorders can be found in Chapters 13 and 14 of this text.