Coronary and Peripheral Vascular Stents
This statement makes it clear that almost all commercially available coronary stent products have been tested and have been stated to be magnetic resonance (MR) safe. Whereas earlier peripheral artery stents (prior to 2007) may be weakly magnetic, all stent products are otherwise safe at ≤3T MRI, and some investigators have confirmed that MR can be performed the same day the stent is placed.
For those peripheral arterial stents that are weakly magnetic, a safety consideration becomes necessary, but magnetic field exposure after 6 weeks is generally considered to be fine.
Therefore, both bare metal stents and drug-coated stents are MR safe.
Mechanical Valves
According to the 2007 AHA statement, almost all commercially available prosthetic heart valves and rings are MR-safe and can be MRI’d at ≤3T at any time.
In addition, the “wire” that holds the sternum in place has also been shown to be MR safe, but there may be local thermal effects due to regional variability in materials.
Therefore, mechanical flaps are also safe.
Cardiac Suturing and Sealing Devices
Most suturing and blocking devices are MR safe. The instructions will indicate whether they have been tested.
Inferior vena cava filters
Most inferior vena cava filters are MR safe, but for a few weakly magnetic devices, such as Cook’s Gianturco bird nest or Boston Scientific’s Greenfield filter, guidelines recommend a 6-week interval between MR exams.
Floating catheters
Patients with Swan-Ganz catheters should not undergo MRI. Although in vivo testing has confirmed that MR images can be obtained safely, there are still possible risks associated with the catheter, guidewire, etc., and MRI is not recommended.
Temporary Pacemakers
Temporary pacing leads retained in the epicardium are MR safe. However, neither extracorporeal pacing with adhesive electrodes nor transvenous temporary pacing is recommended for MR examination.
Pacemakers and ICDs
According to foreign studies, about 50-75% of patients with pacemaker implantation may later require MRI scans. However, in order to avoid interference with the pacemaker due to magnetic fields, a large number of patients with pacemaker implants have been prohibited from undergoing MRI scans in the past.
The greatest risk of MR examinations is the possible displacement of the device, changes in the procedure, interference with the work of the pacemaker itself, or the thermal effects of the electrodes.
Pacemaker and lead systems that can be safely used in MRI systems are available.
IABP
Although no systematic safety evaluation has been performed, the 2007 statement clearly states that IABP is an absolute contraindication to MR.