Safety of Magnetic Resonance Imaging in Patients With Pacemakers and Defibrillators
Condition: Conditions Requiring Diagnostic Evaluation
Study type: Observational

Summary: 
      Pacemakers and ICD's have traditionally been accepted as contraindications to MRI due to
      safety concerns. Recent work in our laboratory as well as our pilot study of approximately
      500 patients has shown the safety of most contemporary implanted rhythm management devices in
      the MRI environment given appropriate precautions. Because the investigators have completed
      testing in animals weighing as little as 80 lbs. without incident, the investigators feel
      they can safely image children at this weight or greater (Circulation 2004; 110:475-482).

      The goal of this study is to expand on our pilot study and to develop a protocol, consistent
      with the Department of Health and Human Services (DHHS) requirements, that will increase our
      safety experience with clinically indicated MR imaging in patients with implanted cardiac
      pacemakers and ICD's.

      This is a cohort study. One thousand seven hundred patients with a clinical need for MRI will
      be recruited. Risks and Benefits associated with Magnetic Resonance (MR) imaging in the
      setting of implantable devices will be discussed and informed consent obtained. The type of
      device and leads will be ascertained. Patients will be monitored by a physician or a
      Registered Nurse (RN) with ACLS certification and familiarity with ICD/Pacemaker programming
      during the study. When imaging children who meet age and weight criteria, a physician will be
      present during the entire study. Fellow and attending radiology and electrophysiology support
      will be available in house in all cases.

      Standard device testing including battery voltages, thresholds, sensing and lead impedances
      will be measured.
    

Detailed description: 
      The primary objective of this study is to develop a protocol, consistent with DHHS/ Center
      for Medicare and Medicaid Services (CMS) guidelines and requirements to further document
      safety in clinically indicated MR imaging in patients with implanted cardioverter
      defibrillators (ICD's) and pacemakers.

      MRI's will be conducted on patients who require a clinically indicated MRI only. All studies
      will be done in the 1.5 Tesla MRI unit. ECG monitoring pads will be placed on the patients
      for the duration of the study. An external defibrillator and Advance Cardiovascular Life
      Support (ACLS) drugs will be on hand. Heart rate, blood pressure, O2 saturation will also be
      monitored non-invasively throughout the study. All devices will undergo a complete
      interrogation prior to imaging. Parameters such as atrial and ventricular pacing thresholds,
      R and P wave amplitudes, lead impedance, and battery status will be measured and recorded.
      PPMs will be programmed to an asynchronous mode if dependent and to an inhibited mode in
      patients without pacemaker dependence.

      The pacemaker function of ICD's in pacemaker independent patients will be programmed to
      ventricular inhibited (VVI) mode at 50 bpm. Pacemaker dependant patients with ICDs will be
      excluded.

      In addition, there is a theoretical concern that patients who have capped or abandoned leads
      in their chest may be at risk for heating. While there is little or no objective data to
      support this concern, given this theoretical concern, patients in this category will only be
      admitted to the study if the referring physician deems the MRI critical and after the PI has
      carefully considered the risk/benefit ration for each patient who falls in to this category.

      Similarly, there historically has also been a concern that newly implanted leads (<4 weeks)
      are at risk for lead to dislodgement d/t possible torque from the MRI environment. This too
      is only a theoretical concern and there is little or no scientific evidence to support this
      claim. Nevertheless, patients with newly implanted pacemaker/ICD leads will be considered by
      the PI for protocol inclusion only if the referring physician deems the MRI to be critical
      and after considering the risk/benefit to each individual patient.

      After the appropriate MRI protocol for each MRI patient's unique condition has been
      completed, the device will be re-programmed to its original settings and completely
      interrogated to detect any changes in device performance.
    

Intervention name(s): Perform MRI in patients with pacemaker or ICD
Intervention type(s): Diagnostic Test
Intervention description(s): Perform MRI in patients with pacemaker or ICD
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        Males and females 9 years old or greater weighing more than 80 lbs who require a clinically
        indicated MRI
      
Biospecimen description: 
      Males and females 9 years or older weighing at least 80 lbs
    
Keywords: MRI; Magnetic Resonance Imaging; pacemakers; ICD