Abstract 621: MRI-related Heating at Cardiac Pacemaker Leads in vivo
Introduction: Currently, MRI is considered a contraindication in pacemaker patients. One main reason is the potential for RF-related heating to appear at pacemaker leads during MRI, as proven in several in vitro investigations. On the other hand, several recent clinical studies found little evidence for adverse events due to pacemaker lead heating in MRI, therefore suggesting relatively small patient risk using modern pacemakers. We aimed at developing a setup for reproducible and precise temperature measurements at the tip of cardiac pacemaker leads in vivo to further substantiate patient hazards.
Methods/Results: Pacemaker leads were equipped with MRI-compatible fluoroptic temperature probes incorporated inside the lead. Feasibility of the measurement method was confirmed in phantom measurements. To determine temperature evolution at the lead tip in vivo, the leads were implanted in the RA/RV/CS in mini pigs (~50kg). Temperature recordings were performed using various scenarios and pulse sequences at 1.5T. The measurement system revealed to be able to precisely measure the temperature evolution at the lead tip in MRI both in vitro and in vivo. A passive fixation lead implanted in the RA from the left jugular vein showed a temperature increase of 14.3K during MRI (30s, 2.1W/kg). Adding a RV lead only slightly affected the amount of heating. Heating was particularly high with the lead placed in the coronary sinus (>15K). Heating of RV leads with the device implanted in either the left and right pectoral region was compared, showing significant heating in both configurations. After euthanizing the pigs, heating increased for further ~15%, suggesting that blood flow hampers but insufficiently prevents unintended heating at cardiac pacemaker leads.
Conclusion: In this study, a new technology for in vivo measurements of unintended heating at pacemaker lead tips in MRI was developed. The preliminary investigations in several configurations prove that significant lead tip heating in vivo can be in the same range as shown for in vitro experiments before. Ongoing investigations focus on the various aspects affecting implant heating in vivo to better specify the risk of relevant heating and, therefore, adverse events in cardiac pacemaker patients undergoing MRI.