DIAPHRAGMATIC MOTION IN PECTUS EXCAVATUM PATIENTS: A COMPARISON WITH HEALTHY SUBJECTS USING A 32-CHANNEL MAGNETIC RESONANCE SYSTEM.

Abstract

Pectus excavatum (PE), or funnel chest, is a congenital chest wall deformity in which the sternum is displaced posteriorly due to abnormal bone and cartilage overgrowth. The condition, with an incidence of 1 in 300 births, often worsens in late adolescence and early adulthood with diminished exercise capacity, chest discomfort, palpitations, easy fatigability, and dyspnea with mild exertion. The etiology of pectus excavatum is unknown; however, several mechanisms have been proposed, including underlying defects of the diaphragm. The aim of this study was to evaluate possible regional abnormalities in diaphragmatic motion in PE using real-time dynamic imaging with magnetic resonance. These data were collected as part of a 3-year study evaluating cardiopulmonary function before and after corrective surgery. Ten patients (pre-corrective surgery, mean age = 22.4) with pectus excavatum deformity and 10 control subjects (mean age = 26) were examined with a two-dimensional GRE sequence, at five frames/sec, using a 1.5-Tesla magnetic resonance system (Avanto, Siemens Medical Solutions, Erlangen, Germany). With the subjects in the supine position, one midcoronal (at the level of trachea bifurcation) slice was obtained during two to five deep respiratory cycles for an average of 50 to 100 measurements. Following data acquisition, image processing was performed on a commercially available image processing workstation (Leonardo, Siemens Medical Solutions) for the largest amplitude respiratory cycle. On sequential images, diaphragmatic displacements were measured for three equally spaced locations (lateral, dome, medial) on each hemidiaphragm to calculate superoinferior diaphragmatic displacement rates. With reference lines on a full expiratory image, the absolute diaphragmatic excursions were calculated as the difference between full inspiratory and full expiratory vertical positions. Pectus excavatum patients had statistically significant (p