Cardiac occluders and closure devices are implants used to treat patients with patent ductus arteriosus (PDA), atrial septal defect (ASD), ventricular septal defect (VSD), or patent foramen ovale (PFO) heart conditions.
For implants that have been evaluated relative to the use of 1.5-T MR systems, as long as the proper size occluder or closure device is used, the amount of retention provided by the folded-back, hinged arms of the device is sufficient to keep it in place, acutely.
Eventually, tissue growth covers the cardiac occluder or closure device and facilitates retention.
Certain metallic PDA, ASD, VSD occluders and PFO closure devices tested for magnetic qualities were made from either 304V stainless steel or MP35N. Occluders made from 304V stainless steel were found to be "weakly" ferromagnetic, whereas those made from MP35N were nonferromagnetic in association with a 1.5-Tesla MR system.
Patients with cardiac occluders made from MP35N (i.e., a nonferromagnetic alloy) may undergo MR procedures at 1.5-Tesla or less any time after placement of these implants. However, patients with cardiac occluders made from 304V stainless steel (i.e., a "weakly ferromagnetic" material) are advised to wait a minimum of six weeks after placement of these devices before undergoing MRI procedures. This wait period permits tissue ingrowth to provide additional retentive forces for the occluders made from weakly ferromagnetic materials.
If there is any question about the integrity of the retention aspects of a metallic cardiac occluder made from a ferromagnetic material, the patient or individual should not be allowed into the MR environment or to undergo an MR procedure.
MRI Information at 3-Tesla and PDA, ASD, VSD Occluders and PFO Closure Devices. Various PDA, ASD, VSD occluders and PFO closure devices have been evaluated at 3-Tesla (see The List). All of these tested to date are considered to be acceptable for patients referred for MR examinations based on findings for deflection angles, torque, MRI-related heating and the intended in vivo uses of these specific devices.
Shellock FG, Morisoli SM. Ex vivo evaluation of ferromagnetism and artifacts for cardiac occluders exposed to a 1.5-Tesla MR system. J Magn Reson Imaging 1994;4:213-215.
Shellock FG, Crues JV, Editors. MRI Bioeffects, Safety, and Patient Management. Biomedical Research Publishing Group, Los Angeles, CA, 2014.
Shellock FG, Valencerina S. Septal repair implants: Evaluation of MRI safety at 3-Tesla. Magnetic Resonance Imaging 2005;23:1021-1025.