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Safety of the MR Conditional MRI Ready ICD System
Study Questions:
What is the safety and efficacy of the St. Jude Medical Durata and Optisure HV leads and Ellipse VR implantable cardioverter-defibrillator (ICD) generator in a 1.5 Tesla magnetic resonance imaging (MRI) environment?
Methods:
This was an investigational device exemption (IDE) study. It was a prospective, multicenter, nonrandomized, single-arm clinical trial evaluating the safety and efficacy of an implanted single-chamber MRI Ready ICD system in patients who had undergone a predefined nondiagnostic MRI scan. No additional non–MRI-compatible hardware (such as an abandoned lead) was allowed to be present. The primary safety objective was >90% freedom from MRI scan-related complications. The primary efficacy objectives were absence of capture threshold change and absence of decrease of sensing amplitude from pre-MRI examination to 1 month post-MRI. After the scan, a questionnaire was given to investigators and patients who underwent a 1-month follow-up visit. A subset of patients had ventricular tachyarrhythmia (VT)/ventricular fibrillation (VF) induction testing performed or collected after the MRI to evaluate defibrillation function.
Results:
There were 220 patients (81% male, average age 62 years) enrolled that received an MRI scan from 29 centers. All primary safety and efficacy endpoints were met (p < 0.0001). No significant detection delays were found in 34 patients who had VT/ VF episodes after the MRI scan was performed. Most physicians reported easy/acceptable programming and ease of MRI scheduling.
Conclusions:
The MRI Ready MRI conditional ICD system is safe and electrical performance was not affected in patients receiving a 1.5 Tesla whole-body MRI scan.
Perspective:
Advances in the field of MRI conditional systems have been possible due to design changes such as use of lesser amounts of ferromagnetic material, removal of Reed switches, and the addition of current filters. This study provides additional clinical data on safety of modern-age ICD systems in the MRI environment. The protocol employed by this and other manufacturers involves disabling tachyarrhythmia detection through programming, which mitigates concerns for device movement, tissue injury due to heating, induced current, electrical resets, and impaired device functionality. This study also highlights the essential role of collaboration between the radiologist and the cardiologist. The next frontier in the field will be changes in the hardware of ICD generators and leads to reduce the field distortion and improve quality of cardiac MRI images.
Clinical Topics: Arrhythmias and Clinical EP, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Prevention, Implantable Devices, EP Basic Science, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure, Magnetic Resonance Imaging, Nuclear Imaging
Keywords: Arrhythmias, Cardiac, Defibrillators, Implantable, Diagnostic Imaging, Electric Countershock, Heart Failure, Magnetic Resonance Imaging, Radionuclide Imaging, Secondary Prevention, Tachycardia, Ventricular, Ventricular Fibrillation
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