Stainless Steel Sternal Wires Are MRI Safe
Yes, stainless steel wires used for sternal closure after cardiac surgery are safe for MRI and are not a contraindication to scanning. Multiple studies and guidelines confirm that metal sternal sutures do not pose significant safety risks during MRI examinations 1.
Safety Evidence
The most comprehensive recent evidence comes from an 8-year retrospective study that found no major adverse events in patients with retained metallic materials after cardiac surgery undergoing MRI 2. A landmark 1997 study of 200 patients with postoperative metallic materials (including sternal wires) found no ECG changes, arrhythmias, or cardiac dysfunction during MRI at 1.5T or 1.5T 3. These findings have been consistently replicated, establishing sternal wires as safe for MRI 1.
Important Distinction: Sternal Wires vs. Epicardial Pacing Wires
Do not confuse sternal closure wires with temporary epicardial pacing wires - these are different devices with different safety profiles:
- Sternal wires: Safe for MRI, not a contraindication 3, 1
- Epicardial pacing wires: The 2021 Canadian guidelines state that "the risk of thermal-mediated cardiovascular injury is likely even lower for active or retained epicardial leads, especially those used for temporary pacing after cardiac surgery" 4, and recent studies show very low event rates (one minor sensory event in 51 scans) 5, 2
Heating Considerations
While a 2020 simulation study demonstrated theoretical RF-induced heating with wire-based sternal closure (peak temperature rises of 9.4°C at 1.5T and 5.8°C at 3T in phantom models) 6, these theoretical concerns have not translated into clinically significant adverse events in real-world practice. The extensive clinical experience spanning decades shows no documented thermal injuries from sternal wires during MRI.
Image Quality Impact
Sternal wires may create artifact on MRI images, particularly in cardiac imaging, but this is an image quality issue, not a safety concern 6. The artifacts do not preclude diagnostic imaging in most cases.
Practical Recommendations
- Proceed with MRI at 1.5T or 3T in patients with sternal wires without special precautions beyond standard MRI safety protocols
- No need for device team involvement or special monitoring (unlike cardiac implantable electronic devices)
- Document presence of sternal wires on pre-scan checklist but do not delay or cancel scanning
- Consider artifact location when planning imaging sequences if cardiac or thoracic imaging is needed
Common Pitfall to Avoid
The most common error is confusing sternal wires with cardiac pacemakers or ICDs, which do require special protocols and device team involvement 4. Sternal wires are passive metallic structures without electronic components and pose fundamentally different (minimal) risks.