Integrated Relaxation Pressure (IRP) Distinguishes between Reflux-Predominant and Dysphagia-Predominant Phenotypes of Esophageal “Absent Contractility”

Background: Patients with absent contractility (AC) often suffer from either reflux or dysphagia. It remains unclear what factors determine which phenotype patients present with. We sought to evaluate if high-resolution manometry metrics, especially integrated relaxation pressure (IRP), could explain this. Methods: Cases of AC from three medical centers were reviewed for demographic, clinical, and manometric data. Cases with an IRP between 10–15 mmHg or subsequent diagnosis of achalasia were excluded. Results: 69 subjects were included (mean age 56.1; 71% female). A total of 41 (59.4%) were reflux-predominant. The reflux-predominant group was younger (51.1 vs. 63.5, p = 0.002) and had lower median LES basal pressures (7.5 vs. 12.5 mmHg, p = 0.014) and IRP values (1.5 vs. 5.6 mmHg, p < 0.001) compared to the dysphagia group. When divided into tertiles, the trend in symptoms between LES basal pressure tertiles was not significant. However, the trend for IRP was significant (p < 0.001). For example, in the lowest IRP tertile, 91.3% of subjects were reflux-predominant compared to only 26.1% in the highest tertile, while the dysphagia-predominant group increased from 8.7% to 73.9%. In a regression model controlling for age and using IRP tertile 1 as the reference, having an IRP in tertile 2 increased the likelihood of having dysphagia-predominant disease by 7, while being in tertile 3 increased the likelihood by 22. Conclusions: IRP helps distinguish between the reflux-predominant and dysphagia-predominant phenotypes of AC. This may have therapeutic clinical consequences as procedures such as fundoplication to tighten the LES may benefit patients with reflux and a low IRP, while procedures like peroral endoscopic myotomy (POEM) to disrupt the LES may benefit patients with dysphagia and a relatively high IRP.