Clinical safety of ProMRI implantable cardioverter-defibrillator systems during head and lower lumbar magnetic resonance imaging at 1.5 Tesla

Abstract

Magnetic resonance imaging (MRI) has long been contraindicated in patients with implanted pacemakers, defibrillators, and cardiac resynchronisation therapy (CRT) devices due to the risk of adverse effects through electromagnetic interference. Since many recipients of these devices will have a lifetime indication for an MRI scan, the implantable systems should be developed as 'MRI-conditional' (be safe for the MRI environment under predefined conditions). We evaluated the clinical safety of several Biotronik ProMRI ('MRI-conditional') defibrillator and CRT systems during head and lower lumbar MRI scans at 1.5 Tesla. The study enrolled 194 patients at 22 sites in Australia, Canada, and Europe. At ≥9 weeks after device implantation, predefined, non-diagnostic, specific absorption rate (SAR)-intensive head and lower lumbar MRI scans (total ≈30 minutes per patient) were performed in 146 patients that fulfilled pre-procedure criteria. Three primary endpoints were evaluated: freedom from serious adverse device effects (SADEs) related to MRI and defibrillator/CRT (leading to death, hospitalisation, life-threatening condition, or potentially requiring implanted system revision or replacement), pacing threshold increase, and sensing amplitude decrease, all at the 1-month post-MRI clinical visit. No MRI-related SADE occurred. Lead values remained stable, measured in clinic and monitored daily by the manufacturer home monitoring technology.

Figure 1

Flow chart of the study. FU: follow-up; MRI: magnetic resonance imaging.

Figure 2

Isocentres at eye and hip level of magnetic resonance imaging scans, the available area for the scans (≈50 cm × 50 cm), and the scan exclusion zone. The size of the usually quadratic field of view varied with body region, scanner manufacturer (Siemens, Philips, GE), and the type of scan sequence (Table 2). The most common field of view was 23 cm × 23 cm, resulting in greater magnetic field gradients and thus more compelling testing conditions than it would be for a larger (e.g. 50 cm × 50 cm) field of view.