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, 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, it is generally not of clinical importance. Rarely, however, the network may be associated with serious complications such as thrombus formation, embolus entrapment, arrhythmia, tumor development, and catheter entrapment. 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.