New Technology: 核磁共振相容節律器 - ”MRI Standard of Care for Pacemaker”)_20130914中區

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New Technology: 核磁共振相容節律器 - ”MRI Standard of Care for Pacemaker”)_20130914中區

  1. 1. New Technology: 核磁共振相容節律器 (MRI Conditional Pacemaker System) 林圀宏 心臟內科 中國醫藥大學附設醫院 2013 心臟電生理相關專業人員教育課程
  2. 2. 輻射線 警告標誌
  3. 3. Why MRI Scans are Important to Clinical Medicine • Fastest Growing Standard of Care in Diagnostic Imaging1 • Superior Soft Tissue Imaging2  Primary method to evaluate:  Central Nervous System  Musculoskeletal System  Oncological Conditions  Some Cardiovascular Disorders • MRI complements CT (which excels when imaging bony structures) • No radiation risk to patient or healthcare provider • Since the absence of x-ray radiation, MRI is optimal for follow-up of chronic diseases that require repeat imaging and for diagnostic imaging in young patients and women of childbearing age. 1. Kaiser CP. Soaring MRI use draws scrutiny. Diagnostic Imaging Online January 4, 2002. CMP United Business Media: A CMP Healthcare Media Web Site. Available at: http://www.diagnosticimaging.com/dinews/2002010401.shtml. Accessed October 19, 2004. 2. Duru F, Luechinger R, Scheidegger MB, et al. Pacing in magnetic resonance imaging environment: Clinical and technical considerations on compatibility. Eur Heart J. January 2001;22(2):113-124.
  4. 4. Cervical spine computed tomography (CT) vs MRI in a patient with neck pain and fever. Nazarian S et al. Circ Arrhythm Electrophysiol 2013;6:419- 428 Copyright © American Heart Association
  5. 5. Brain computed tomography (CT) vs MRI in a patient with weakness. Nazarian S et al. Circ Arrhythm Electrophysiol 2013;6:419- 428 Copyright © American Heart Association
  6. 6. Cardiac computed tomography (CT) vs MRI in a patient with facial swelling. Nazarian S et al. Circ Arrhythm Electrophysiol 2013;6:419- 428 Copyright © American Heart Association
  7. 7. Complication while having MRI
  8. 8. 核磁共振 (MRI) 警告標誌
  9. 9. 10 Anatomy of an MRI Scanner Three basic components:  Static magnet  Gradient magnets  RF coil 10 Static Determines magnetic strength of scanner:  1.5 or 3.0 tesla  1 tesla (T) = 10,000 gauss.  The earth’s magnetic field = 0.5 gauss.  Magnet response in SJM pacemakers occurs in response to 8-10 gauss directly over the pacemaker.
  10. 10. Force • The most intuitive potential interaction of implanted devices with an external magnetic field is the possibility for movement and dislocation of the device because of magnetic force. • Current lead designs contain little or no ferromagnetic components and are not likely to experience force and torque. • The potential for movement of a pacemaker or ICD generator in the MRI environment depends on the  magnetic field strength  ferromagnetic properties of the device components  the implant distance from the magnet bore and the stability of the implant.
  11. 11. Current induction • The RF and pulsed gradient magnetic fields of the MRI scanner may induce electric currents in leads within the field, if the lead is part of a current loop that is completed through the body. • The ratio of lead length versus RF wavelength and lead conformations, such as loops, are strongly associated with the extent of current induction.
  12. 12. Gradient Waveform Amplitude 0.4 ms 500 ms – 750 ms Pacing Pulse Time ~ 0.005 ms Gradient Induced Pulse Gradient Induced Pulse Gradient Mechanism
  13. 13. Stimulation hazard gradient-induced high rate pacing Start of Scan EKG Pulse Ox Canine Test Unintended Stimulation Clinical Impact The MRI scanner is pacing the heart
  14. 14. Heating and tissue damage • Metallic devices and leads can act as an antenna thus amplifying local radiofrequency energy deposition. • Fractured leads or lead loop configurations may increase the potential for heating. • Epicardial leads that are not cooled by blood flow and abandoned leads may also be prone to increased heating.
  15. 15. Heating of cardiac tissue Heating at the lead tip can result in threshold changes.
  16. 16. Malfunction of devices • CIED may provide unnecessary therapies or fail to provide necessary therapies when placed in the MRI scanner. • Pacemakers and ICDs have the potential for receiving electromagnetic interference (EMI) in the MRI environment, resulting in:  radiofrequency noise tracking  asynchronous pacing  inhibition of demand pacing  delivery of ICD therapies  programming changes  loss of function.
  17. 17. Figure 2. EMI noise from different MR scan protocols interpreted by the device as ventricular fibrillation (VF). Roguin A et al. Circulation 2004;110:475-482
  18. 18. Simultaneous electrocardiography and pulse oximetry while in 3T bore of magnetic resonance imaging followed by application of gradient scan leading to inhibition of effective pacing. Gimbel J R Europace 2009;11:1241-1242
  19. 19. Malfunction of devices • The static magnetic field of the MRI scanner can also alter device function by inducing unexpected reed switch opening or closure. • In addition, temporary programming changes made to avoid device interaction with the MRI scanner (such as disabling of tachycardia therapies) may lead to catastrophic results if a spontaneous arrhythmia occurs and is not recognized.
  20. 20. Simultaneous recording of ECG and pulse oximetry during MRI of the brain in a patient with a Thera pacemaker reprogrammed to D00 80 bpm. Sommer T et al. Circulation 2006;114:1285-1292 Copyright © American Heart Association
  21. 21. During and/or after the MRI • no inhibition of pacemaker output or cardiac arrest • no sustained ventricular arrhythmias • no unexpected changes of heart rate • no electrical resets • no pacemaker system disturbances and • no sensation of torque or pain
  22. 22. Variables Affecting Magnitude of Risks  Length/position of pacing leads  Patient and device position within machine  Patient factors / medical history  MRI scan duration  Blood flow at lead/tissue interface  Strength of RF field  Target anatomy of scan  Type of imaging MRI sequence  Pacemaker and Lead Design
  23. 23. MR Conditional Labeling* MR Safe MR Conditional MR Unsafe An item that has been demonstrated to pose no known hazards in a specified MRI environment with specified conditions of use.
  24. 24. Device Design Solutions • Minimize ferromagnetic content • Hybrid-case connection • Hall sensor • Optimize input circuitry
  25. 25. Solutions to Reduce MRI Risk • Filter board added to pacemaker hardware • When the filter detects MRI RF signals, it will not allow the signals to be sent back down the lead (rectification), which would result in cardiac stimulation. . 28 X-ray marker MRI filter assembly
  26. 26. Solutions to Reduce MRI Risk • 2 filters are incorporated into the pacing lead to reduce the risk of heating from RF signals.
  27. 27. PATIENT MANAGEMENT
  28. 28. Patient Care Pathway 1. Pre-Screening and Scheduling 2. Pre-scan 3. Scan 4. Post-Scan
  29. 29. Pre-screening • Ways to ID pacemaker system: 1. Patient ID Card 2. X-Ray 3. Call cardiology
  30. 30. Patient ID Card
  31. 31. X-Ray Radiopaque identifies the system via unique radiopaque visible under x-ray 1 Location of the device radiopaque symbol 2 Device radiopaque MRI symbol 3 Lead radiopaque MRI symbol
  32. 32. Radiopaque identification available: 1. pulse generator 2. lead
  33. 33. 36 MRI Pacemaker Identification
  34. 34. MRI Pacemaker Identification (Con’t) • To verify that a patient has a MRI pacemaker, you may use X-ray identification, confirming that the pacemaker and the lead are appropriate. Radiopaque markers will show if the patient has an appropriate system for an MRI scan 37 St. Jude Medical Identifier Device MRI Symbol
  35. 35. To program MRI SureScan to On, go to Params -> Additional Features.
  36. 36. When programmed to On, MRI SureScan operation disables • Arrhythmia detection, • Magnet mode, • All user-defined diagnostics. On
  37. 37. • For patients who require pacing support, program the device to an asynchronous pacing mode (DOO, AOO, VOO). • For patients who do not require pacing support, program the device to the non-pacing mode (ODO).
  38. 38. Patients and their implanted systems must be screened to meet the following requirements: •No previously implanted (active or abandoned) medical devices, leads, lead extenders, or lead adaptors. •No broken leads or leads with intermittent electrical contact as confirmed by lead impedance history. •A SureScan pacing system that has been implanted for a minimum of 6 weeks. •A SureScan pacing system implanted in the left or right pectoral region. •Pace polarity parameters set to Bipolar for programming MRI SureScan to On (for Advisa DR MRI). •Pacing capture thresholds of ≤ 2.0 volts (V) at a pulse width of 0.4 milliseconds (ms). •A lead impedance value of ≥ 200 ohms (Ω) and ≤ 1500 Ω. •No diaphragmatic stimulation at a pacing output of 5.0 V and at a pulse width of 1.0 ms in patients whose device will be programmed to an asynchronous pacing mode when MRI SureScan is on. Cardiology requirements:
  39. 39. Radiology requirements
  40. 40. -45- Competitive Comparison SJM Accent MRI™ Static magnet 1.5 T- closed bore Scan Zones Fully body scan SAR Restrictions Max SAR 4W/kg MRI settings activation without programmer Yes- SJM MRI Activator™ device Wireless Telemetry Yes Daily Remote Monitoring Yes
  41. 41. Preparing Accent MRI Patient for an MRI Scan
  42. 42.  Seamless workflow when a patient needs an MRI  No programmer needed at MRI center  No impact to clinic efficiencies MR Pacemaker Establish MRI Settings Values Settings (Follow-up Appt) Patient Needs MRI Scan MRI Scan DeviceClinicMRICenter MRI Center Arrival MR Mode OFF Button MR Mode ON Button  Simple application of the MRI Activator pre- and post-scan No programmer necessary for MRI access = Additional programming step required by competitive systems 48 Pre-Scan Follow-up (optional)
  43. 43. Preparing Accent MRI Patient for an MRI Scan (Con’t) Traditional MRI patient workflow process
  44. 44. Preparing Accent MRI Patient for an MRI Scan (Con’t) St. Jude Medical streamlined MRI patient workflow
  45. 45. Take Home Message • Implantable pulse generators and defibrillators have traditionally been considered contraindications to MRI. • Patients with newer generation devices (MRI conditional device) can safely undergo MRI, including cardiac MRI. • But, the introduction of MRI conditional systems has led to a conceptual shift in clinical decision making — ‘can this patient undergo MRI safely?’ is being superseded by ‘should this patient be implanted with an MRI conditional device?’. • Perform MRI carefully in Pacemaker-dependent patients

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