Chiari Network Entanglement and Herniation into the Left Atrium by an Atrial Septal Defect Occluder Device

The Chiari network is a fenestrated membrane consisting of threads and strands in the right atrium. First described in 1897 by anatomist Hans Chiari, 1 it is a congenital remnant of embryonic development resulting from incomplete resorption of the right valve of the sinus venosus. Found in 2% to 3% of the population, 2,3 it is generally not of clinical importance. Rarely, however, the network may be associated with serious complications such as thrombus formation, 2 embolus entrapment, 4 arrhythmia, 5 tumor development, 6 and catheter entrapment. 7 We report the entanglement of an Amplatzer septal occluder device catheter in a prominent Chiari network that was herniated into the left atrium. Transesophageal echocardiographic recognition of this before deployment and guidance during disentanglement is described below. (J Am Soc Echocardiogr 1999;12:601-3.)