Alexandra Schmiedel MD, Presenter: Nothing to Disclose

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

Katharina Strach MD, Abstract Co-Author: Nothing to Disclose

Carsten Meyer, Abstract Co-Author: Nothing to Disclose

Hans H. Schild MD, Abstract Co-Author: Research Consultant, Dainippon Sumitomo Pharma Co, Ltd

Torsten Sommer MD, Abstract Co-Author: Research Consultant, Medtronic, Inc, Minneapolis, MN

To evaluate safety and feasibility of extrathoracic magnetic resonance imaging (MRI) in patients with implantable cardioverters/defibrillators (ICD).

Patient examinations: Inclusion criteria were presence of an ICD and the urgent clinical need for an MRI exam. Patients requiring examinations of the thoracic region were excluded. The study group consisted of 10 ICD patients who underwent a total of 10 MRI exams at 1.5 Tesla. To minimize radiofrequency-related lead heating, the specific absorption rate was limited to 1.5W/kg. All ICD were reprogrammed pre-MRI: 1. Therapy delivery was inactivated and arrhythmia detection was activated. 2. The pacing mode was reprogrammed to VVI 40bpm. 3. SAR was limited to 1.5W/kg to minimize RF exposure of the ICD system. Patients were monitored using ECG and pulse oximetry. All ICD 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.

Patient examinations: All MR exams were completed safely. There was no significant change in PCT (p>0.05), pacing lead impedance (p>0.05) and shock impedance (p>0.05). Battery voltage decreased significantly (p0.05). MRI did not affect the programmed data of the ICD nor the feasibility of interrogating, programming or telemetry. During the MRI exam 50% (5 of 10) of the ICD revealed oversensing of the RF-fields as ventricular fibrillation at post-MRI PM interrogation, but no therapy delivery was attempted by the devices.

Our initial experience indicates that extrathoracic MR imaging at 1.5T in patients with ICD might be feasible and safe in carefully selected cases when appropriate strategies are used: 1. Deactivation of therapy delivery. 2. Reprogramming the pacing mode to VVI 40 bpm. 3. Limitation of SAR to 1.5 W/kg of sequences used.

Extrathoracic MRI of ICD 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, Strach, K, Meyer, C, Schild, H, Sommer, T, Strategy for Safe Performance of Extrathoracic MRI at 1.5T in Patients with Implantable Cardioverters/Defibrillators.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5015542.html