Patient Orientation Affects Lead-Tip Heating of Cardiac Active Implantable Medical Devices during MRI

To evaluate changes in patient orientation to mitigate radiofrequency-induced lead-tip heating (LTH) during MRI.

LTH was evaluated for device type, lead path, and distance to the isocenter of a 1.5-T MRI system. LTH for 378 conditions in both head-first (HF) and feet-first (FF) orientations was measured for nine MRI-unsafe cardiac active implantable medical devices (AIMDs) placed along three (two anatomic, one planar) left-sided lead paths at nine landmark locations. The devices were exposed to 5 minutes of continuous radiofrequency energy at 4 W/kg whole-body specific absorption rate.

LTH was greater in HF than in FF orientation for the planar and one anatomic lead path (P < .05). LTH was significantly affected by lead path, distance to isocenter, and patient orientation (all P < .05), but not by cardiac AIMD device type. Maximum LTH was observed in an HF orientation for the planar lead path when the lead tip was at isocenter (right ventricular [RV] lead: 32.0 °C ± 16.3 [standard deviation], right atrial [RA] lead: 16.1°C ± 9.3). In the FF orientation, LTH was significantly reduced (RV lead: 1.6°C ± 1.4; mean RA lead: 0.5°C ± 1.0; P = .008).

LTH for supine FF patient orientations among patients with anterior left-sided cardiac AIMDs can be significantly lower than LTH for supine HF orientations. There was no scenario in which LTH was significantly worse in the FF position. Changing patient orientation is a simple method to reduce radiofrequency-induced LTH.© RSNA, 2019See also the commentary by Litt in this issue.