Vector volume analysis of the lower esophageal sphincter in achalasia and the effect of balloon dilation.

Assessment of the effect of balloon dilation of the lower esophageal sphincter in achalasia currently relies on symptom scores, radiologic studies, or manometry. We have used vector volume analysis which constructs a three-dimensional (3D) pressure profile to examine the effects of balloon dilation on the sphincter. Studies were performed in 26 normal subjects and in 11 patients with achalasia in whom vector volume was determined before and/or after balloon dilation. Vector volume analysis was performed using a multilumen manometry catheter with eight side-reading ports. The catheter was withdrawn through the sphincter using a continuous pull-through technique. A 3D pressure profile was constructed. Vector volume of the lower esophageal sphincter shows a marked radial and linear asymmetry in normal subjects. 3D pressure profiles showed a symmetrical increase in lower esophageal sphincter pressure in untreated achalasia. Mean vector volumes pre and postdilation fell from 254 to 88 cm3 respectively. This was associated with a fall in the mean radial symmetry index from 0.83 to 0.76. Improvement in dysphagia occurred in those patients in whom pressure fell to 15 mmHg or below in at least three adjacent segments. This technique may be a useful tool in the assessment of patients with achalasia and postdilation results may help to predict the long-term outcome of treatment.