Safety evaluation of a leadless transcatheter pacemaker for magnetic resonance imaging use

Background Increased magnetic resonance imaging (MRI) adoption and demand are driving the need for device patients to have safe access to MRI. Objective The aim of this study was to address the interactions of MRI with the Micra transcatheter pacemaker system. Methods A strategy was developed to evaluate potential MRI risks including device heating, unintended cardiac stimulation, force, torque, vibration, and device malfunction. Assessment of MRI-induced device heating was conducted using a phantom containing gelled saline, and Monte Carlo simulations incorporating these results were conducted to simulate numerous combinations of human body models, position locations in the MRI scanner bore, and a variety of coil designs. Lastly, a patient with a Micra pacemaker who underwent a clinically indicated MRI scan is presented. Results Compared to traditional MRI conditional pacemakers, the overall risk with Micra was greatly reduced because of the small size of the device and the absence of a lead. The modeling results predicted that the nonperfused temperature rise of the device would be less than 0.4°C at 1.5 T and 0.5°C at 3 T and that the risk of device heating with multiple device implants was not increased as compared with a single device. The clinical case study revealed no MRI-related complications. Conclusion The MRI safety assessment tests conducted for the Micra pacemaker demonstrate that patients with a single device or multiple devices can safely undergo MRI scans in both 1.5- and 3-T MRI scanners. No MRI-related complications were observed in a patient implanted with a Micra pacemaker undergoing a clinically indicated scan.