The major objective of this study was to refine the diagnostic criteria for hypercontractile peristalsis, drawing from a large clinical experience with EPT studies. Based on an analysis of 72 control subjects, the threshold DCI value for hypercontractility was established to be a single contraction with a DCI value greater than 8,000 mmHg-s-cm, thereby exceeding any value encountered in control subjects. Thereafter, hypercontractility was subgrouped into that with and without multipeaked contractions. These different groups presented similar characteristics (normal distal contractile latency, normal peristaltic contractile velocity) and similar outcomes. Since the repetitive, high amplitude contractions evoke the action of a jackhammer, we coined the descriptive term Jackhammer Esophagus with the defining criterion of at least one peristaltic contraction with a DCI value greater than 8,000 mmHg-s-cm. In this series of 1,070 consecutive patients encountered in a tertiary esophageal referral practice, Jackhammer Esophagus was decidedly rare, seen in only 44 (4.1%) with the dominant symptom being dysphagia about 70% of the time. The clinical presentation was diverse; some Jackhammer Esophagus cases were clearly associated with mechanical EGJ outflow obstruction, others secondary to reflux disease, and some attributable to primary esophageal muscle hypercontractility.
The development of EPT has greatly clarified our understanding of the segmental architecture of peristalsis (20
). Rather than occurring as a seamless process, peristalsis occurs through the sequential activation of four discrete contractile segments spanning from the proximal striated muscle to the lower esophageal sphincter. After realizing this architecture, Clouse observed that double peaked contractions occurred as a consequence of the overlap and imperfect coordination between the adjacent second and third contractile segments. He further observed that although double peaked contractions could occur normally, they were more likely to occur in swallows with strong contraction in the third segment (18
). Those observations are borne out in the current series, evident by the occurrence of multipeaked contractions in 3% of control subjects and by the dominant localization of hypercontractility to the third contractile segment detailed in . In this paradigm, Jackhammer esophagus is best conceptualized as extreme hypercontractility in the third contractile segment.
The Clouse hypothesis of the genesis of multipeaked contractions detailed above is not universally accepted. Alternatively, it has recently been proposed that multiple peaked swallows might be an artifact (19
). Indeed, the distal esophagus and diaphragm are attached at the EGJ causing them to move in unison during respiration, which could cause the appearance of a multipeaked pattern of contraction attributable to oscillatory movement of the contracting esophagus relative to the sensor recording that contraction. This was proposed by Sampath et al
. in a study of the synchrony between respiration and pressure peaks in patients with multipeaked contractions (19
). Suspended breathing and hyperventilation modified the esophageal contraction waveform morphology accordingly. In view of those observations, we systematically explored the synchrony between multipeaked contractions and respiration. Multipeaked contractions were synchronized with respiration in roughly half of the Jackhammer patients whereas in the other half they were not. There was no apparent clinical difference between these subsets ( and ). Furthermore, although the respiratory oscillation hypothesis may suffice to explain a multipeaked contraction at the spatial margins of the contractile segment in some instances, this explanation is clearly insufficient to explain the extreme oscillations spanning the entire contractile segment illustrated in and .
Hypercontractility may also result from EGJ obstruction. Experimental EGJ obstruction caused esophageal smooth muscle hypertrophy and excitability in the opossum (21
). In humans, gastric banding represents a model of EGJ obstruction and band inflation can induce hypertensive and repetitive esophageal contractions (22
). Finally Gyawali recently showed that patients with EGJ outflow obstruction might exhibit a spastic motor pattern characterized by multipeaked contractions, high distal esophageal amplitude and prolonged contraction duration (23
). This may have been the cause of hypercontractility in some of our patients evident by the abnormal IRP values observed in 8 of them (19%) (). However, there was minimal correlation between DCI and IRP within the Jackhammer group.
The pathophysiology of Jackhammer Esophagus is largely unknown beyond that patients with hypertensive contractions have been noted to have increased esophageal muscle thickness on ultrasound (24
) and exhibit an atropine-sensitive asynchrony between the circular and the longitudinal muscle contraction (25
). Consequently, excess cholinergic drive may be a distinguishing feature. Another argument for a role of the cholinergic pathway in the genesis of mulitpeaked contractions comes from observations in diabetics with autonomic neuropathy. Loo et al.
reported that a higher frequency of multipeaked waves in diabetics with autonomic neuropathy than in diabetics without neuropathy or controls (27
). These multipeaked contractions occurred in a context of normal peristaltic amplitude and were converted to single peaked contractions after atropine injection. We also observed instances of Jackhammer Esophagus in GERD patients consistent with prior reports of hypercontractility in patients with reflux disease (4
). Relatively few patients in our series had pH monitoring studies done, but about 10% had reflux esophagitis on endoscopy and anti-reflux therapy was also associated with the resolution of symptoms in 8 of 15 patients and normalization of EPT studies in 1 of 2 cases who had follow-up studies. Further studies are required to evaluate the respective roles of EGJ obstruction, reflux disease and cholinergic modulation in patients with Jackhammer Esophagus.
This study has some limitations attributable to its retrospective design. No validated dysphagia questionnaire was used leaving us without a precise symptom profile of Jackhammer patients. There was also no controlled approach to treatment of this decidedly rare disorder (only 4.1% of our series). A variety of treatments were proposed based on individual patient characteristics with variable success. This variability emphasizes the heterogeneity of the patient population exhibiting esophageal hypercontractility.
In conclusion, we described an extreme phenotype of esophageal hypercontractility characterized in EPT by the occurrence of at least a single contraction with DCI >8,000 mmHg-s-cm. This phenomenon, branded Jackhammer Esophagus, was never encountered in control subjects and was usually accompanied by a dominant symptom of dysphagia. Further studies are required to define the pathophysiology and treatment of this disorder.