MRI Safety in Patients with Remote Stent Placement
Patients with remotely placed stents can safely undergo MRI at any time after stent placement, regardless of stent location (coronary, carotid, or other vascular territories), with no waiting period required. 1, 2
Safety Profile by Stent Type
Coronary Artery Stents
- Current coronary stents are MRI-safe at field strengths up to 3 Tesla and do not pose migration or thrombosis risks. 1, 2
- No waiting period is necessary after coronary stent placement before performing MRI, despite older manufacturer recommendations suggesting an 8-week delay. 3, 4
- Studies demonstrate no increased cardiac events (death, myocardial infarction, or stent thrombosis) when MRI is performed as early as the day of stent placement. 3, 5
- Both bare metal stents (BMS) and drug-eluting stents (DES) are safe for immediate MRI scanning. 4, 5
Carotid and Intracranial Stents
- Carotid artery stents are MRI-safe, though almost all sternal wires, clips, stents, occlusion devices, and prosthetic valves within the chest are safe in a 1.5T magnet. 6
- For carotid stent follow-up, noninvasive imaging including MRI is reasonable at 1 month, 6 months, and annually after revascularization. 6
- Intracranial stents (such as the WingSpan stent with lower metal density) result in minimal artifact on MRI. 6
Other Vascular Stents
- Nickel-titanium alloy stents (commonly used in airways and other vessels) are not at risk of dislodgement or heating during MRI. 7
- Stainless steel stents may shift in a magnetic field depending on the specific steel type used, requiring verification of the specific stent model. 7
Technical Imaging Considerations
Artifact Production
- Coronary stents cause local artifacts that prevent visualization of the coronary lumen in the immediate stent region, but this affects image quality, not safety. 1, 2
- For coronary artery evaluation specifically, cardiac CT is superior to cardiac MRI for assessing stent patency and integrity. 1
- Artifacts extend approximately 16 mm on T1-weighted spin echo sequences and 23 mm on gradient echo sequences around the stent. 5
Field Strength
- MRI systems with field strength up to 3 Tesla are safe for patients with coronary and other vascular stents. 8, 5
- Higher field strengths do not increase the risk of stent migration, heating, or thrombosis. 4, 5
Pre-MRI Screening Protocol
Essential Safety Checks
- All patients must be screened using a standardized checklist for MRI contraindications, including verification of implant type, location, and material. 6, 9
- Obtain the patient's implant pass and verify the device's MRI safety classification: MRI unsafe (absolute contraindication), MRI conditional (relative contraindication with specific conditions), or MRI safe (no contraindication). 6, 9
- Remove all metallic items including jewelry, clothing with zippers or buttons, and transdermal patches containing metal. 6, 9
Critical Distinctions
- While vascular stents are MRI-safe, cardiac pacemakers and implantable cardioverter-defibrillators generally remain contraindications for MRI. 1, 2
- Ferromagnetic cerebral aneurysm clips and steel fragments near the brain or retina remain absolute contraindications. 6, 9
Common Pitfalls to Avoid
- Do not delay clinically indicated MRI based on outdated manufacturer recommendations about waiting 8 weeks after stent placement. 3, 4
- Do not confuse the safety profile of vascular stents with that of active cardiac devices (pacemakers, defibrillators), which have different risk profiles. 1, 2
- For stainless steel stents specifically, verify the exact steel composition, as some types may have ferromagnetic properties. 7
- When imaging near the stent location, recognize that artifact will limit visualization of the immediate stent area, but alternative imaging (CT) can be used if stent patency assessment is needed. 6, 1