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The article by Martin et al. (1) suggesting that magnetic resonance imaging (MRI) examinations are safe in qualified pacemaker patients should lead to improved care, especially for cancer patients. Encouraged by this article, we have taken two patients into a Signa LX EchoSpeed 1.5-T MRI (GE Medical Systems, Milwaukee, Wisconsin). Our second patient experienced difficulties not previously noted, demonstrating the need for continued caution when performing these exams.
A 48-year-old man with a left-sided, dual-chamber pacemaker placed on August 1, 1997, for neurogenic syncope (Thera DR 7960i,Medtronic Corp., Minneapolis, Minnesota) had metastatic multiple myeloma and significant pain. The MRI was performed to evaluate lower extremity neurologic deficits after attempted intrathecal catheter implantation.
The thoracic and lumbar spine regions were evaluated by sagittal fast spin echo (FSE) T2-weighted pulse sequences with fat saturation and pre/post contrast T1-weighted FSE pulse sequences in the sagittal and axial planes. Compared to previous computed tomography (CT) myelogram, MRI revealed more extensive cord compression at T9–10 from epidural tumor. The MRI demonstrated no epidural hematoma, possibly preventing an unnecessary laminectomy. A CT examination performed one month previously, because of pacemaker contraindication to MRI, demonstrated no epidural involvement.
Pacemaker evaluation immediately before MRI showed adequate battery voltage and impedance (Fig. 1)with DDDR pacing (lower rate 60, upper sensor and tracking rates 135 beats/min). M.A.R. (an anesthesiologist “facile in the ways of pacemaker programming”) disabled pacemaker rate responsiveness and monitored the patient with pulse oximetry plethysmography and electrocardiography (Millennia 3155 MVS monitor, In Vivo Research, Orlando, Florida). This monitor has no pacemaker artifact enhancement in the remote (MRI) mode.
Upon entering the MRI room, pacemaker magnet mode was activated (DOO pacing, 85 beats/min) until patient alignment with the MRI tunnel (heart rate returned to 74 beats/min). During MRI, pacing appeared to remain in DDD mode, with heart rates between 68 and 82 beats/min. Occasional pseudofusion beats were noted, but the ECG tracing was unreliable during MRI sequences. PVCs were noted during and between MRI scan cycles. No medication was given, and the patient did not complain of palpitations or chest pain (although he had back pain). He was quickly removed from the MRI upon completion of the 1.5-h exam.
Immediate pacemaker interrogation revealed onset of elective replacement (ERI) with a programming change to VVI pacing at 65 beats/min despite normal battery voltage and impedance (Fig. 2).This change eliminated all pacemaker diagnostic data storage. The “STATUS RESET” function in the programmer returned the pacemaker to dual-chamber function, and no other abnormalities were found.
It is unclear why our patient's pacemaker detected an ERI condition. Medtronic Thera platforms (including Prodigy, Preva, Kappa 400, and Insynch 8040) can be especially sensitive to electromagnetic interference signals entering via the telemetry coil, which might account for our observation in this case. Although no inappropriate ERI was found in the Martin et al. (1) series, which included 12 of these platforms (but only one Thera device), no thoracic spine MRI examinations were performed.
This outcome reminds us that significant pacemaker problems might still occur during MRI, despite the experience of Martin et al. (1). Although their report will likely permit better care of pacemaker patients, the caveat that special care of these patients appears necessary. We believe that recommendations from Martin et al. (1) should be strengthened. Rather than simply available, a physician who is “facile in the ways of pacemaker programming” should be present to monitor the patient, as suggested by Gimbel and Kanal (2). Additionally, the entire team caring for patients in the MRI suite needs to be prepared to quickly and immediately remove the patient from the MRI should a significant problem be discovered.
- American College of Cardiology Foundation
- Martin E.T.,
- Coman J.A.,
- Shellock F.G.,
- Pulling C.C.,
- Fair R.,
- Jenkins K.
- Gimbel J.R.,
- Kanal E.