Impedance planimetry

Abstract

Impedance planimetry is an imaging technique that provides in vivo esophageal distensibility data in real time. A catheter equipped with a cylindrical bag is gradually distended with a conductive solution. Impedance and intrabag pressure readings are used to calculate the distensibility index as ratio of the cross-sectional area at the narrowest spot to intrabag pressure. In healthy volunteers esophagogastric junction distensibility, obtained at 40 mL bag filling volume, shows a wide variation of 2.7–7.1 mm2/mmHg. In achalasia patients distensibility is significantly lower (≤1.6 mm2/mmHg) and normalizes after successful treatment. Post-interventional distensibility index values in the range of 4.5–8.5 mm2/mmHg predict good outcome. Impedance planimetry imaging has recently been integrated into a dilatation catheter for treatment of achalasia and a feasibility study reported technical success in all therapeutic interventions using this device. In patients affected by eosinophilic esophagitis distensibility of the esophagogastric junction is lower than in healthy controls and in the tubular esophagus a distension plateau is reached at a narrower luminal diameter, reflecting the remodeling of the esophageal wall in this disease. In patients with small hiatal hernias impedance planimetry is able to display the lower esophageal sphincter and the crural diaphragm as spatially separated regions of reduced distensibility. Each component is more distensible than the single esophagogastric junction in subjects without hiatal hernia. Conflicting data exist regarding esophagogastric junction distensibility in patients with gastroesophageal reflux disease. Two studies found higher and one reported lower values compared to asymptomatic controls. Intra- and postoperative impedance planimetry studies showed that laparoscopic antireflux surgery results in a significant reduction of esophagogastric junction distensibility, being significantly more pronounced after a Nissen than a Toupet fundoplication. Impedance planimetry is the only diagnostic tool available in clinical routine to examine mechanical wall properties in vivo. It complements other diagnostic procedures like endoscopy, videofluoroscopy, and high-resolution (impedance) manometry in the assessment of esophageal function in various disease states and has become a valuable tool for monitoring and tailoring therapeutic interventions.