Does Gastric Retention Pattern Affect Outcome of Gastric Peroral Endoscopic Myotomy for Patients with Gastroparesis? A Preliminary Study

Abstract

Introduction: Gastroparesis is a disease of impaired gastric motility characterized by nausea, vomiting, early satiety and bloating. Gastric emptying scintigraphy (GES) is primarily used for diagnosis. Gastric per-oral endoscopic pyloromyotomy (G-POEM or POP) has emerged as a novel technique for treating gastroparesis with up to an 80% success rate. As this procedure involves pyloromyotomy, we hypothesize that responders to this therapy are characterized by a more distal retention pattern on GES when compared with non-responders. Methods: This is a retrospective study with IRB approval. We used standardized 4-hour GES as per the SNMMI procedure guideline to quantify proximal and distal retention using the incisura as an anatomical landmark, separating two regions (Figures 1 and 2). Baseline and post-procedure symptom severity were measured using the Gastroparesis Cardinal Symptoms Index (GCSI). Responders were defined by a reduction of at least 1 point in total GCSI and a 25% reduction in at least 2 of the 3 symptom subscales. We compare treatment response and symptom profile in each patient to total gastric half-emptying time (T1/2), proximal gastric T1/2 and a ratio comparing the proximal to total gastric T1/2, which we call retention index (RI). RI serves as a proxy for retention location, with a larger value representing more proximal disease.749_A Figure 1. Proximal stomach selection on gastric emptying scintigraphy in anterior (left) and posterior (right) projections.749_B Figure 2. Distal stomach selection on gastric emptying scintigraphy in anterior (left) and posterior (right) projections.Results: 47 patients underwent G-POEM during the study period. A significant difference (P<0.01) was found in pre-procedure RI between responders and non-responders (Figure 3). A decrease in RI was identified for each patient following the procedure. No significant differences were identified in baseline total or proximal T1/2 between the two groups. No correlations were found between motility patterns and predominant symptoms.749_C Figure 3. Pre-procedure Retention Index vs. Total GCSI Reduction. Note that all responders had RI value greater than 0.84, as indicated by the dashed red line, and all non-responders had RI less than this value.Conclusion: RI was significantly higher in responders. This may represent an important patient selection factor for G-POEM going forwards. A higher RI indicates a more proximal burden of disease. Perhaps the effect of pyloromyotomy goes beyond local distensibility, similarly to how fundic distension can induce antroduodenal motor activity. Larger, prospective studies are warranted to further explore RI as a criterion for G-POEM selection and the correlation between anatomical retention and motor activity. G-POEM has a clear, measurable effect on gastric emptying as shown by the decrease in RI following the procedure. Regional retention patterns may not correlate well with gastroparesis symptoms.