Alexandra Schmiedel MD, Presenter: Nothing to Disclose

Claas Philip Naehle MD, Abstract Co-Author: Nothing to Disclose

Matthias Hackenbroch MD, Abstract Co-Author: Nothing to Disclose

Carsten Meyer MD, Abstract Co-Author: Nothing to Disclose

Hans Heinz Schild MD, Abstract Co-Author: Nothing to Disclose

Torsten Sommer MD, Abstract Co-Author: Nothing to Disclose

To evaluate a strategy for safe performance of extrathoracic magnetic resonance imaging (MRI) in patients with cardiac pacemakers (PM) who are non-PM dependent.

Inclusion criteria were presence of an cardiac PM and the urgent clinical need for an MRI examination. Pacemaker dependent patients and those requiring examinations of the thoracic region were excluded. The study group consisted of 82 PM patients who underwent a total of 115 MRI exams at 1.5 Tesla. To minimize radiofrequency-related lead heating, the specific absorption rate was limited to 1.5W/kg. All pacemakers were reprogrammed pre-MRI: If heart rate 60 bpm, sense-only mode to avoid MR-induced competitive pacing and potential proarrhythmia. Patients were monitored using ECG and pulse oximetry. All PM were interrogated immediately prior to and after the MRI exam, and after 3 months, including measurement of pacing capture threshold (PCT) and serum troponin I levels.

All MR exams were completed safely. Inhibition of PM output or induction of arrhythmias was not observed. Pacing capture threshold (PCT) increased significantly from pre-MRI to post-MRI (p=0.017). In 2 of 195 leads, an increase in PCT was only detected at 3-month follow-up. In 4 out of 114 examaminations, the troponin level increased from a normal baseline value to above normal afterwards, in one case (troponin pre-MRI 0.02ng/ml, post-MRI 0.16ng/ml) associated with a significant increase of PCT, possibly due to RF related heating of the PM lead tip. In no examination (0/115) a change of programmed PM output was required.

No clinically significant alteration of PM function was observed after 115 MR examinations at 1.5T, although an increase of serum troponin post MRI indicating thermal myocardial injury was found.

Extrathoracic MRI of non-pacemaker dependent patients can be performed with a acceptable risk-benefit-ratio under controlled conditions, and by taking both MR and PM related precautions.

Schmiedel, A, Naehle, C, Hackenbroch, M, Meyer, C, Schild, H, Sommer, T, Strategy for Safe Performance of Extrathoracic MRI at 1.5T in the Presence of Cardiac Pacemakers in Non-Pacemaker Dependent Patients: A Prospective Study with 115 MR Exams.  Radiological Society of North America 2006 Scientific Assembly and Annual Meeting, November 26 - December 1, 2006 ,Chicago IL. http://archive.rsna.org/2006/4437568.html