March

Cardiac Magnetic Resonance Imaging (MRI) in Children is Safe with Most Pacemaker Systems, Including Those with Epicardial Leads. Bireley M, Kovach JR, Morton C, Cava JR, Pan AY, Nugent M, Samyn MM. Pediatr Cardiol. 2020 Mar 12. doi: 10.1007/s00246-020-02316-z. PMID: 32166409 Similar articles   Take Home Points: MRI scanning at 1.5 T in patients with active/functional epicardial pacing leads appears does not appear to affect pacemaker or lead functionality. Hemodynamically stable native rhythm permits simplified ODO device programming during MRI scanning. In pediatric and young adult patients with transvenous and epicardial pacing systems, MRI scanning at 1.5 T appears to be safe provided a systematic approach is taken to scan planning, performance, and follow-up.     Comment from Dr. Philip Chang (Gainesville, FL), section editor of Congenital Heart and Pediatric Cardiac Electrophysiology Journal Watch: This study by Bireley et al retrospectively reviewed their single center experience with performing MRI studies in pediatric and young adult patients with permanent pacemakers over an 8-year period (2010-2018). Electronic records review was performed on a cohort of patients formulated by performing a query for all patients with “pacemakers” and “MRI” in records documentation. The institution had an existing protocol for managing pacemaker patients before, during, and after MRI scans. This involved pre-scan evaluation and clearance for the MRI following confirmation of a hemodynamically stable underlying rhythm when the pacemaker was programmed to ODO, pre-scan and post-scan device interrogations and re-programming, and then 2 serial outpatient visits (first visit after MRI and 6 months post-MRI). During the MRI scan itself, an “EP representative” and MRI cardiologist were present to ensure patient safety and stability. Demographic data, MRI-specific data, and pacemaker/lead data including implant date, manufacturer and model, and generator location were collected and analyzed.   A total of 21 patients who underwent 44 MRI studies were included in this study (median age 10.9 yo, 18/21 with CHD). The majority of patients had Medtronic devices (17/21) and only 3/21 generators were labeled as MRI-conditional. The majority of patients had active epicardial leads as well (17/21). All scans were performed with a 1.5 T MR scanner, of which 17/44 (39%) were primary cardiac scans. Over half of the scans were brain MRI’s (25/44, 57%) and the remaining 4% were musculoskeletal. There were no adverse events during or after MRI scans that could be attributed to the scans themselves or a scan-associated alteration in pacemaker/lead functionality. The authors reported no significant changes in pacemaker or lead functionality over ensuing device checks immediately after the scan, at first follow-up post-scan, and at 6-month follow-up post-scan. There was a statistically significant change in battery voltage (2.78 V pre-MRI to 2.77 V at follow-up, p 0.02). (see copied figure)     There are substantial limitations to this study. The retrospective design and electronic records search yielded a very small cohort of patients. Many device patients were likely excluded from MRI scans. Given the scanning protocol that was instituted, only patients with a stable underlying rhythm were scanned. However, the percentage of those who were scanned among all pacemaker patients (i.e. those with and without stable underlying rhythms) was not reported. Scans were only performed in the ODO programmed mode, but it would have been very useful to see data regarding scans with devices programmed for asynchronous pacing (and thereby including patients who would be considered pacemaker-dependent). Subjects with ICD’s were also excluded. The authors also did not include or discuss patients with abandoned leads, particularly abandoned epicardial leads, which is another group of patients who are frequently excluded from MRI studies. There was no discussion regarding the impact of implanted devices on the quality of scanned images, namely cardiac or abdominal structures, as a result of the presence of pacemakers and leads and associated artifact. And finally, contrary to the title of the study, this was not an exclusive cardiac MRI-based study, with <40% of the scans being primarily cardiac MRI’s.   Perhaps the greatest values of this study are: 1) the demonstration of safe performance of MRI studies in patients with active epicardial leads, and 2) the value of an organized approach to scanning patients with pacemakers. Concern over lead heating remains one of the main reasons why patients with epicardial leads are excluded from MRI’s. It was helpful to see that there were no adverse events attributable to heating in the study cohort, of which the majority were patients with epicardial leads. Finally, the study demonstrated the value, but also the potential personnel burden, of having a systematic approach to performing MRI studies in patients with pacemaker systems. With the potential for growth in numbers of scans performed, especially as the evidence for safety of scanning becomes more robust, it can be anticipated that requiring an “EP representative” and cardiologist at every scan (including those that are not primarily cardiac MRI’s) will need to assessed.