title: The figure-of-eight artifact in the echocardiographic assessment of percutaneous disc occluders: impact of imaging depth and device type.
abstract: OBJECTIVE
  Echocardiography is increasingly important in the guidance and follow-up of percutaneous transcatheter device closures. It was recently shown that the Amplatzer left atrial appendage occluder frequently presents as a figure-of-eight artifact due to interaction of device mesh and ultrasound waves. It remains unknown whether this can be translated to other types of disc occluders. Furthermore, the morphology of this figure-of-eight artifact appears to be different in the transesophageal and transthoracic image of the same device. The aim of this study was to evaluate the echocardiographic appearance of different types of disc occluders, and to clarify differences in morphology of the figure-of-eight artifact.
  
  
  METHODS
  A mathematical model of an epitrochoid curve was used for numerical simulation of disc occluder appearance at various imaging depths. In addition, an in vitro setup was used for echocardiographic analysis of different types of disc occluders at adjustable imaging depth and position.
  
  
  RESULTS
  Mathematically, decreasing the imaging depth resulted in a more asymmetric figure-of-eight, i.e. with small upper part and wide lower part. In vitro results were in close agreement with the mathematical results. In addition, in vitro a figure-of-eight artifact was obtained in all different types of disc occluder devices.
  
  
  CONCLUSIONS
  Different types of percutaneous disc occluders all present as a figure-of-eight artifact on echocardiography when imaged from a coronal imaging position. The morphology of the artifact depends on the imaging depth, with a more asymmetric figure-of-eight morphology at smaller probe-to-device distance. This clarifies the differences observed between transesophageal and transthoracic imaging.
authors.affiliation: Department of Cardiology, Ziekenhuis Oost-Limburg, Genk, Belgium; Faculty of Medicine and Life Sciences, Hasselt University, Hasselt, Belgium.
authors.forename: Philippe B
authors.initials: PB
authors.lastname: Bertrand
authors.forename: Lars
authors.initials: L
authors.lastname: Grieten
authors.forename: Christophe J P
authors.initials: CJ
authors.lastname: Smeets
authors.forename: Frederik H
authors.initials: FH
authors.lastname: Verbrugge
authors.forename: Wilfried
authors.initials: W
authors.lastname: Mullens
authors.forename: Mathias
authors.initials: M
authors.lastname: Vrolix
authors.forename: Maximo
authors.initials: M
authors.lastname: Rivero-Ayerza
authors.forename: David
authors.initials: D
authors.lastname: Verhaert
authors.forename: Pieter M
authors.initials: PM
authors.lastname: Vandervoort
mesh_terms: D016477:Artifacts; D004452:Echocardiography / Q000295:instrumentation* / Q000379:methods*; D019544:Equipment Failure Analysis; D019047:Phantoms, Imaging; D011474:Prosthesis Design; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D055989:Septal Occluder Device
keywords: echocardiography; in vitro testing; mathematical modeling; percutaneous closure devices; ultrasound physics