Safety of brain 3-T MR imaging with transmit-receive head coil in patients with cardiac pacemakers: pilot prospective study with 51 examinations

PURPOSE: To evaluate the safety and feasibility of 3-T magnetic resonance (MR) imaging of the brain in patients with implanted cardiac pacemakers (PMs) by using a transmit-receive head coil. MATERIALS AND METHODS: The study protocol was approved by the institutional review board. Signed informed consent was obtained from all subjects. In vitro testing at 3 T was performed with 32 PMs and 45 PM leads that were evaluated for force and torque (by using a floating platform) and radiofrequency (RF)-related heating by using a transmit-receive head coil (maximum specific absorption rate, 3.2 W/kg). Patient examinations at 3 T were performed in 44 patients with a cardiac PM and a strong clinical need; patients underwent a total of 51 MR examinations of the brain by using a transmit-receive head coil to minimize RF exposure of the PM system. An electrocardiograph and pulse oximetry were used for continuous monitoring during MR imaging. The technical and functional PM status was assessed prior to and immediately after MR imaging and at 3 months thereafter. Serum troponin I level was measured before and 12 hours after imaging to detect myocardial thermal injury. PM reprogramming was performed prior to MR imaging depending on the patient's intrinsic heart rate ( or = 60 beats per minute, sense-only mode). RESULTS: For in vitro testing, the maximum translational force was 2150 mN (mean, 374.38 mN +/- 392.75 [standard deviation]), and maximum torque was 17.8 x 10(-3) N x m (mean, [2.29 +/- 4.08] x 10(-3) N x m). The maximum temperature increase was 2.98 degrees C (mean, 0.16 degrees C +/- 0.45). For patient examinations, all MR examinations (51 of 51) were completed safely. There were no significant (P < .05) changes in lead impedance, pacing capture threshold level, or serum troponin I level. CONCLUSION: MR imaging of the brain at 3 T in patients with a cardiac PM can be performed safely when dedicated safety precautions (including the use of a transmit-receive head coil) are taken

Safety, feasibility, and diagnostic value of cardiac magnetic resonance imaging in patients with cardiac pacemakers and implantable cardioverters/defibrillators at 1.5 T

BACKGROUND: Recent studies suggest that magnetic resonance (MR) imaging of the brain and spine may safely be performed in patients with pacemakers (PMs) and implantable cardioverter/defibrillators (ICDs), when taking adequate precautions. The aim of this study was to investigate safety, feasibility, and diagnostic value (DV) of MR imaging in cardiac applications (cardiac MR [CMR]) in patients with PMs and ICDs for the first time. METHODS: Thirty-two PM/ICD patients with a clinical need for CMR were examined. The specific absorption rate was limited to 1.5 W/kg. Devices were reprogrammed pre-CMR to minimize interference with the electromagnetic fields. Devices were interrogated pre-CMR and post-CMR and after 3 months. Troponin I levels were measured pre-CMR and post-CMR; image quality (IQ) and DV of CMR were assessed. RESULTS: All devices could be reprogrammed normally post-CMR. No significant changes of pacing capture threshold, lead impedance, and troponin I were observed. Image quality in patients with right-sided devices (RSD) was better compared with that in patients with left-sided devices (LSD) (P < .05), and less myocardial segments were affected by device-related artefacts (P < .05). Diagnostic value was rated as sufficiently high, allowing for diagnosis, or better in 12 (100%) of 12 patients with RSD, and only in 7 (35%) of 20 patients with LSD. CONCLUSIONS: Cardiac MR may be performed safely when limiting specific absorption rate, appropriately monitoring patients, and following device reprogramming. Cardiac MR delivers good IQ and DV in patients with RSD. Cardiac MR in patients with RSD may therefore be performed with an acceptable risk/benefit ratio, whereas the risk/benefit ratio is rather unfavorable in patients with LSD. Copyright © 2011 Mosby, Inc. All rights reserved

Effects of repetitive prolonged breath-hold in elite divers on myocardial fibrosis and cerebral morphology

Background: Prolonged apnea by breath-hold (BH) divers leads to hypoxemia and compensatory mechanisms of the cardiovascular system (i.e. increase of total peripheral resistance, increase of systolic blood-pressure, left-ventricular enlargement) to maintain oxygen supply to oxygen sensitive organs such as the brain. All these changes may result in structural myocardial or subclinical brain alterations. Therefore, the aim of this study was to investigate mid-term effects of repetitive prolonged apnea using cardiac magnetic resonance imaging (CMR) and magnetic resonance imaging of the brain. Materials and methods: 17 elite BH divers (15 males) were investigated at baseline, from whom 9 (7 males) were investigated again at follow-up one year later. CMR included functional imaging and tissue characterization using T1-and T2-mapping as well as late gadolinium enhancement. Results were compared intra-individually and with 50 age matched controls. Results: Mean BH time were 297 +/- 52 s (entire cohort) and 315 +/- 56 s (sub-cohort) at initial, and 334 +/- 104 s at follow-up examination. Apnea resulted in a progressive increase of the left ventricle and impaired function, whichfully resolved after cessation of apnea. At rest, no dilation of the left ventricle was notable (LV-EDV: 106.7 +/- 28.8 ml; LV-EDV/BSA: 52.2 +/- 12.7 ml/m(2)). Compared to controls, the apnea group showed significantly lower volumes (LV-EDV: 106.7 +/- 28.8 ml vs. 140.9 +/- 36.3 ml, p = .008; LV-EDV/BSA: 52.2 +/- 12.7 ml/m(2) vs. 73.7 +/- 12.8 ml/m2). In contrast, LV-EF showed no significant differences between both groups (61.0 +/- 7.0% vs. 60.9 +/- 3.6%). T1-and T2-mapping revealed no significant differences, neither intra-individually nor in comparison with age matched controls. (T1 pre-contrast: 974.1 +/- 12.9 ms vs. 969.4 +/- 29.0 ms, p = .2; T1 post-contrast: 368.9 +/- 38.5 ms vs. 966.7 +/- 40.5 ms, p = .4; ECV: 29.2 +/- 1.5% vs. 29.8 +/- 1.6%, p = .3; T2. 52 +/- 2 ms vs. 52 +/- 3 ms; p = .4). Except for one old embolic lesion no structural changes were found in brain imaging. Conclusion: Although, prolonged apnea leads to impressive adaptions of the cardiovascular system (i.e. dilation of the left ventricle) and hypertension due to peripheral vasoconstriction no mid-term morphological changes could be observed in both, the myocardium and the brain. BH divers are suitable as a model to investigate acute physiological changes of prolonged apnea and hypoxemia, but not as a model for chronic alterations