MedicalResearch.com Interview with:
Robert Russo, MD, PhD, FACC
The Scripps Research Institute
The La Jolla Cardiovascular Research Institute
MedicalResearch.com: What is the background for this study?
Response: For an estimated 2 million people in the United States and an additional 6 million people worldwide, the presence of a non-MRI-conditional pacemaker or implantable cardioverter defibrillator (ICD) is considered a contraindication to magnetic resonance imaging. This creates a dilemma for at least half of these patients, who are predicted to require an MRI scan during their lifetime after a cardiac device has been implanted. Safety concerns for patients with an implanted cardiac device undergoing MRI are related to the potential for magnetic field-induced cardiac lead heating resulting in myocardial thermal injury, and a detrimental change in pacing properties. As a result, patients with an implanted device have long been denied access to MRI, although it may have been the most appropriate diagnostic imaging modality for their clinical care. Despite the development of MRI-conditional cardiac devices, a strategy for mitigating risks for patients with non MRI-conditional devices and leads will remain an enduring problem for the foreseeable future due to an ever increasing demand for MRI and the large number of previously and currently implanted non-MRI-conditional devices.
MedicalResearch.com: What are the main findings?
Response: MRI was performed for 1000 cases with a pacemaker and 500 with an ICD. No deaths, lead failures, loss of capture, or ventricular arrhythmias occurred during MRI. One ICD generator required replacement due to inappropriate device programming that was a protocol violation. Six cases of self-terminating atrial fibrillation and 6 of partial electrical reset were observed. A change in device settings after MRI occurred in a small number of patients. Repeat MRI was not associated with an increase in adverse events. Leads placed less than 90 days prior to MRI did not have a higher rate of complications.
MedicalResearch.com: What should readers take away from your report?
Response: Clinically indicated nonthoracic MRI may be performed at a field strength of 1.5 tesla without harm when patients with a non-MRI-conditional pacemaker or ICD are appropriately screened and monitored and the device is appropriately reprogrammed during the MRI scan. The observed event rate in MagnaSafe was equal to or lower than the yearly spontaneous failure rate of pacemaker or ICD generators; clinical results that may be very difficult to improve upon with the development of MRI-conditional devices.
Patients could undergo MRI without a limitation for time since lead or generator implantation (A total of 63 cases underwent MRI within 90 days of initial generator placement or replacement). Although patients with an ICD who were pacing-dependent were excluded from the study, this exclusion was adopted because not all devices available at the time of study initiation could accommodate independent programming of bradycardia and tachycardia functions. Lastly, these results strongly imply that no patient with a standard cardiac device should ever be exposed to the morbidity of generator replacement or lead extraction, nor should access be denied due to the inaccurately perceived and overestimated risk of appropriately performed and monitored non-thoracic MRI.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Response: Our next investigation, scheduled to soon begin, will involve an assessment of risk for patients undergoing clinically indicated MRI of the chest (thorax) at a field strength of 1.5 tesla, and MRI of any anatomic location at a field strength of 3.0 tesla.
MedicalResearch.com: Any disclosures?
Response: This investigator-initiated research study was funded by grants from Biotronik, Boston Scientific, St. Jude Medical, and The Hewitt Medical Research Foundation, as well as multiple philanthropic sources. The authors were solely responsible for the design and conduct of the MagnaSafe Registry without any involvement of the funding sources.
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