Background: 
Cardiac magnetic resonance imaging (MRI), a key method guiding medical diagnosis and therapy, is increasingly performed at 3 Tesla (T) field strength. Growing evidence suggests a relatively safe conductance of 1.5 T MRI in patients with cardiac implantable electronic devices (CIEDs), leading to conditional certification of some CIEDs for MRI. However, data on the safety of MRI imaging at 3 T in patients with CIEDs are scarce.  

Aim: 
We analysed the safety of clinically indicated 3 T MRI in patients with ‘3T MRI-conditional’ and ‘3 T MRI-non-conditional’ CIEDs.

Methods:
We performed a retrospective single-center analysis of consecutive patients with CIEDs labelled by the manufacturer as ‘MRI non-conditional’, ‘1.5 T MRI-conditional’ and ‘3 T MRI-conditional’. Patients underwent clinically indicated 3 T MRI of different thoracic and non-thoracic body regions from April 2020 to October 2021. Devices were interrogated and programmed appropriately before and after scanning. Statistics included median and interquartile range. Measurements of device and lead function and integrity before and after scanning were assessed. Adverse events included all-cause death, arrhythmias, loss of capture, inappropriate anti-tachycardia therapies, electrical reset and lead or generator failure during or shortly after MRI scan.

Results:
Sixty-seven 3 T MRI scans were performed in 46 patients (mean age 69 ± 16.25 years, 43.5% female). 3T MRI scans were performed in patients with ‘non-MRI-conditional’ devices (n=8), ‘1.5 T MRI-conditional’ devices (n=19), and ‘3 T MRI-conditional’ devices (n=40).  Patients were pacemaker-dependent in twelve MRI scans. 

After MRI, lead impedance had changed by 100 Ohms or more in four cases (2 atrial and 2 right ventricular leads). P-wave (-25%) and R-wave (-50%) reduction was noted in one case each. All changes were found in ‘3 T MRI-conditional’ devices. No clinically relevant adverse events occurred.

Conclusion:

3 T MRI was safely conducted in patients with `3 T MRI-conditional’ and ‘non-MRI conditional’ CIEDs in our single-center study. Pending verification in independent series, our data suggest that clinically indicated 3T MRI scans should not be withheld from patients with cardiac pacemakers or defibrillators.