MRI Safety in Post-CABG Patients
MRI is safe to perform in patients with a history of CABG, as coronary artery stents, prosthetic cardiac valves, metal sternal sutures, mediastinal vascular clips, and epicardial pacing wires are not contraindications for MRI. 1
Safety Profile of Post-CABG Hardware
The materials commonly retained after CABG surgery do not pose significant risks during MRI:
- Sternal wires (stainless steel) are safe for MRI scanning, though they may create imaging artifacts that can interfere with interpretation 1, 2
- Mediastinal vascular clips used during surgery are MRI-safe 1, 3
- Epicardial pacing wires (temporary wires cut short at the skin) can be safely scanned and do not produce cardiac arrhythmias or dysfunction during MRI 3
- Coronary artery stents and prosthetic cardiac valves are explicitly not contraindications for MRI 1
Clinical Evidence Supporting Safety
A study of 200 post-cardiac surgery patients who underwent MRI at 1.0 or 1.5 Tesla demonstrated complete safety, with no patients reporting symptoms of arrhythmia or cardiac dysfunction during scanning 3. Among 81 patients monitored with ECG during MRI, no changes from baseline cardiac rhythms were detected 3. This included 51 patients with retained temporary epicardial pacing wires 3.
Important Contraindications to Recognize
While CABG-related hardware is safe, you must screen for these absolute contraindications:
- Permanent pacemakers remain contraindicated for MRI in non-MRI conditional devices, as heating of pacemaker leads is the major safety concern 1
- Implantable cardioverter-defibrillators (ICDs) are contraindicated unless they are MRI-conditional devices 1
- The FDA states there are currently neither "MRI-safe" nor "MRI-compatible" non-conditional pacemakers and ICDs 1
Practical Imaging Considerations
When performing MRI on post-CABG patients:
- Artifact production: Sternal wires and hemoclips create imaging artifacts that may reduce diagnostic quality, particularly when evaluating graft patency 2
- Graft evaluation: MRI can successfully evaluate bypass graft patency, with accuracy rates of 85% for LAD grafts, 91% for RCA grafts, and 97% for circumflex grafts 2
- Field strength: Both 1.0 and 1.5 Tesla MRI systems have been validated as safe in post-CABG patients 3
Pre-Scan Screening Protocol
Before proceeding with MRI in a post-CABG patient, verify:
- Absence of permanent pacemaker or ICD (unless MRI-conditional) 1, 4
- Chest radiograph confirmation of retained metallic materials to anticipate artifact locations 3
- Risk-benefit analysis ensuring the diagnostic benefit outweighs any theoretical risks 1
Common Pitfalls to Avoid
- Do not assume all cardiac devices are contraindications—CABG hardware specifically is safe 1
- Do not confuse temporary epicardial pacing wires (safe) with permanent pacemaker systems (contraindicated) 1, 3
- Do not delay necessary MRI imaging in post-CABG patients without pacemakers/ICDs, as the procedure is well-validated as safe 3, 4