Strategy for Safe Performance of Extrathoracic Magnetic Resonance Imaging at 1.5 Tesla in the Presence of Cardiac Pacemakers in Non–Pacemaker-Dependent Patients

Abstract

Background-The purpose of the present study was to evaluate a strategy for safe performance of extrathoracic magnetic resonance imaging (MRI) in non-pacemaker-dependent patients with cardiac pacemakers. Methods and Results-Inclusion criteria were presence of a cardiac pacemaker and 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 pacemaker patients who underwent a total of 115 MRI examinations at 1.5T. To minimize radiofrequency-related lead heating, the specific absorption rate was limited to 1.5 W/kg. All pacemakers were reprogrammed before MRI: If heart rate was Ͻ60 bpm, the asynchronous mode was programmed to avoid magnetic resonance (MR)-induced inhibition; if heart rate was Ͼ60 bpm, sense-only mode was used to avoid MR-induced competitive pacing and potential proarrhythmia. Patients were monitored with ECG and pulse oximetry. All pacemakers were interrogated immediately before and after the MRI examination and after 3 months, including measurement of pacing capture threshold (PCT) and serum troponin I levels. All MR examinations were completed safely. Inhibition of pacemaker output or induction of arrhythmias was not observed. PCT increased significantly from pre-to post-MRI (Pϭ0.017). In 2 of 195 leads, an increase in PCT was only detected at follow-up. In 4 of 114 examinations, troponin increased from a normal baseline value to above normal after MRI, and in 1 case (troponin pre-MRI 0.02 ng/mL, post-MRI 0.16 ng/mL), this increase was associated with a significant increase in PCT. Conclusions-Extrathoracic MRI of non-pacemaker-dependent patients can be performed with an acceptable risk-benefit ratio under controlled conditions and by taking both MR-and pacemaker-related precautions.

Magnetic resonance imaging in patients with a pacemaker system designed for the magnetic resonance environment

“…16, These findings of potential RF-related thermal injury are further supported by in-vitro experiments 4,18,19 and in-vivo animal studies. 3,4 The leads of this new pacemaker system were modified to reduce lead tip heating …”

“…Variations among different lead models can result in different risks of lead tip heating. 15 Publications have shown that substantial increases in PCT 16,17 and serum troponin 16 can be observed after MRI at 1.5T in patients implanted with conventional pacemakers.…”

“…It is notable that in previous studies 5,16 that performed MRI scans on patients with conventional pacemakers in off-label use, cardiac myocardial injury, as indicated by increases in PCT and troponin I levels, was not entirely eliminated, even with strict precautionary measures to minimize the risk of RF lead heating. This trial showed only one increase in PCT from pre-to post-MRI/control visit (control group) >0.…”

MR Imaging in Patients with Cardiac Pacemakers and Implantable Cardioverter Defibrillators

“…Before and after MR examination, statistically significant but very small and clinically irrelevant changes in the pacing capture threshold, impedance, and battery voltage [2] could be observed in pacemaker patients and lengthening of the charging time and a decrease in battery voltage [26] were seen in ICD patients. A small (< 20 %) change in amplitude in the right atrium and right ventricle was observed in approximately 80 % and 90 % of device patients, respectively.…”

Role of the lead structure in MRI‐induced heating: In vitro measurements on 30 commercial pacemaker/defibrillator leads

“…The results of these studies demonstrated that the devices in use today may be more resistant to changes in function during an MR examination. To date, data on more than 1000 patients who underwent clinically driven MRI are available (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11). Even if some adverse events were observed (11), in most cases no serious injuries have been reported in physician-supervised MRI studies during which the patients were carefully monitored, and only minor effects were observed (minor changes in pacing threshold, the need for device reprogramming, possibly battery depletion).…”