Description of a new clinical syndrome: thoracic constriction without evidence of the typical funnel-shaped depression-the "invisible" pectus excavatum.

Pectus excavatum (PE) is a congenital malformation with a funnel-shaped depression of the sternum that can lead to cardiac symptoms. However, there are patients with thoracic constriction (defined as elevated Haller-Index > 3.25 determined by cardiac magnetic resonance imaging (CMR)) without visible evidence of PE, leading to similar complaints.