Initial evaluation should include imaging, particularly noncontrast computed tomography or magnetic resonance imaging.
22,23 These imaging modalities allow visualization of the malformation and can reveal cardiac compression, cardiac displacement, and the presence of atelectasis or tracheobronchial compression.
22 Computed tomographic images should be obtained on both inspiration and expiration because the severity of the defect may substantially worsen when a patient exhales (
Figure 2).
24 Imaging is used to calculate the index of severity at the lowest level of the pectus malformation, generally using the Haller index or the correction index. The Haller index is calculated using the width of the chest divided by the distance between the posterior surface of the sternum and the anterior surface of the spine.
25 A Haller index score is normal at 2.5 to 2.7 and severe at 3.25 or greater.
25,26 The correction index uses an equation of (
b−
a)/
b×100, in which
a is the minimum distance between the anterior spine and the posterior surface of the sternum, and
b is the maximum distance between the anterior spine and most anterior internal rib.
15,27 It yields a percentage that the chest would need to be corrected to achieve normal dimensions, with a normal level being 10% or less.
15 The correction index better assesses patients with a more barrel-shaped chest who have a Haller index score that is falsely low.
15,27