Safety of MRI in patients with CV devices By Dr S. Sanyal MBBS, MS, MSc (UK), ADPHA, ADHRD Consultant Surgeon & Associate Professor Seychelles

Study highlights CV devices MRI mechanisms MRI risk determinants FDA classification of CV devices Recommendations Conclusions Reference Addendum

CV devices

MRI mechanisms

MRI risk determinants

FDA classification of CV devices

Recommendations

Conclusions

Reference

Addendum

Examples of CV devices Coronary stents Peripheral stents Aortic stent grafts Embolization coils IVC filters

Coronary stents

Peripheral stents

Aortic stent grafts

Embolization coils

IVC filters

Examples of CV devices Prosthetic heart valves Annuloplasty rings Cardiac closure / occluder devices Loop recorders Retained fractured intravenous leads

Prosthetic heart valves

Annuloplasty rings

Cardiac closure / occluder devices

Loop recorders

Retained fractured intravenous leads

Examples of CV devices Pacemakers Implantable cardioverter defibrillators (ICD) Hemodynamic support devices Intra-aortic balloon pumps (IBP) Right ventricular (RV) assist devices Left ventricular (LV) assist devices

Pacemakers

Implantable cardioverter defibrillators (ICD)

Hemodynamic support devices

Intra-aortic balloon pumps (IBP)

Right ventricular (RV) assist devices

Left ventricular (LV) assist devices

Recommendations for CV devices in general Screening : Patients with CV device requiring MRI should undergo screening to accurately identify the implanted device Temporary devices : Inpatients should be examined for temporary devices

Screening : Patients with CV device requiring MRI should undergo screening to accurately identify the implanted device

Temporary devices : Inpatients should be examined for temporary devices

MRI safety No ionizing radiation Non-invasive procedure No iodinated contrast agents

No ionizing radiation

Non-invasive procedure

No iodinated contrast agents

MRI risk mechanisms Static magnetic field Radiofrequency (RF) energy Gradient magnetic fields

Static magnetic field

Radiofrequency (RF) energy

Gradient magnetic fields

Static magnetic field 1.5 to 3 Tesla , which corresponds to 30,000 - 60,000 times the strength of earth's magnetic field Scanners are typically superconducting Thus, they are always ‘on’.“ Attraction of a ferromagnetic object into the scanner

1.5 to 3 Tesla , which corresponds to 30,000 - 60,000 times the strength of earth's magnetic field

Scanners are typically superconducting

Thus, they are always ‘on’.“

Attraction of a ferromagnetic object into the scanner

Recommendation for static Devices should be non-ferromagnetic or weakly ferromagnetic (most are) Lowest field strength available to minimize ferromagnetic risk

Devices should be non-ferromagnetic or weakly ferromagnetic (most are)

Lowest field strength available to minimize ferromagnetic risk

RF energy RF energy pulsed into body to generate the MR image -> ohmic heating . Metallic devices (e.g. lead) act as antennae -> concentrate RF energy -> excessive local heating at device tip Electrical currents created in wires / leads -> arrhythmias.

RF energy pulsed into body to generate the MR image -> ohmic heating .

Metallic devices (e.g. lead) act as antennae -> concentrate RF energy -> excessive local heating at device tip

Electrical currents created in wires / leads -> arrhythmias.

Gradient magnetic field Rapidly changing magnetic fields Excite peripheral nerves Induce electrical currents in conductive devices . Flow of electricity in conductive blood produce ECG changes / arrhythmias

Rapidly changing magnetic fields

Excite peripheral nerves

Induce electrical currents in conductive devices .

Flow of electricity in conductive blood produce ECG changes / arrhythmias

Risk determinants MRI emergency / elective Material of CV device ferromagnetic / weakly ferromagnetic / non-ferromagnetic Specific type of device

MRI emergency / elective

Material of CV device

ferromagnetic / weakly ferromagnetic / non-ferromagnetic

Specific type of device

MRI elective vs. emergency Knee pain for 5 years and needs an MRI but has just had a device implanted 2 days ago Vs. Admitted to hospital after being hit by a car; acute knee pain; surgeons want urgent MRI

Knee pain for 5 years and needs an MRI but has just had a device implanted 2 days ago

Vs.

Admitted to hospital after being hit by a car; acute knee pain; surgeons want urgent MRI

Material of CV device Non-metallic safer than metallic Among metallic Non-ferromagnetic < weak ferromagnetic < strong ferromagnetic

Non-metallic safer than metallic

Among metallic

Non-ferromagnetic < weak ferromagnetic < strong ferromagnetic

Recommendations based on material Non-ferromagnetic ‘passive’ implant (e.g. titanium, titanium alloy, nitinol) MRI immediately after implantation Weakly ferromagnetic devices MRI 6 weeks after implantation

Non-ferromagnetic ‘passive’ implant (e.g. titanium, titanium alloy, nitinol)

MRI immediately after implantation

Weakly ferromagnetic devices

MRI 6 weeks after implantation

Specific type of device Obsolete FDA definitions – ‘ MR safe’ / ‘MR compatible’ Current FDA definitions – ‘ MR safe’ ‘ MR conditional’ ‘ MR unsafe’

Obsolete FDA definitions –

‘ MR safe’ / ‘MR compatible’

Current FDA definitions –

‘ MR safe’

‘ MR conditional’

‘ MR unsafe’

MR safe Non-metallic Non-conducting Nonmagnetic

Non-metallic

Non-conducting

Nonmagnetic

MR conditional No known hazards in a specified MR environment with specific conditions

No known hazards in a specified MR environment with specific conditions

MR unsafe Known to pose hazards in all MR environments

Known to pose hazards in all MR environments

Specific recommendations Those pacemakers that have been tested have been labelled “MR unsafe” Pacemaker / ICD – strong relative contraindication to MR examination Scan only at experienced centres Written informed consent. Clinician with pacemaker / ICD expertise Crash cart including defibrillator

Those pacemakers that have been tested have been labelled “MR unsafe”

Pacemaker / ICD – strong relative contraindication to MR examination

Scan only at experienced centres

Written informed consent.

Clinician with pacemaker / ICD expertise

Crash cart including defibrillator

Specific recommendations Known retained fractured intravenous leads Poses a high risk for thermal injury . MR examination should not be performed

Known retained fractured intravenous leads

Poses a high risk for thermal injury .

MR examination should not be performed

Specific recommendations Hemodynamic support devices (IBP, RV / LV assist devices) with variable ferromagnetic / electrical components Absolute contraindications to MR examination

Hemodynamic support devices (IBP, RV / LV assist devices) with variable ferromagnetic / electrical components

Absolute contraindications to MR examination

Specific recommendations Coronary / peripheral vascular stents, cardiac occluder devices, embolization coils Most considered ‘MR safe’ Some considered ‘MR conditional’ MRI can be conducted with non-ferromagnetic stents

Coronary / peripheral vascular stents, cardiac occluder devices, embolization coils

Most considered ‘MR safe’

Some considered ‘MR conditional’

MRI can be conducted with non-ferromagnetic stents

Specific recommendations Most aortic stent grafts that have been tested are labelled ‘MR safe’ Only Zenith AAA endovascular graft (Cook Vascular, Inc) is labelled ‘MR unsafe’.

Most aortic stent grafts that have been tested are labelled ‘MR safe’

Only Zenith AAA endovascular graft (Cook Vascular, Inc) is labelled ‘MR unsafe’.

Specific recommendations Most prosthetic heart valves / annuloplasty rings that have been tested are labelled ‘MR safe’ Some are ‘MR conditional’

Most prosthetic heart valves / annuloplasty rings that have been tested are labelled ‘MR safe’

Some are ‘MR conditional’

Specific recommendations Loop recorders that are considered ‘MR conditional May experience slight movement of the device during MRI Should be warned to avoid undue concern

Loop recorders that are considered ‘MR conditional

May experience slight movement of the device during MRI

Should be warned to avoid undue concern

Conclusion MRI risks arise from 3 mechanisms Static magnetic field RF energy Gradient magnetic fields

MRI risks arise from 3 mechanisms

Static magnetic field

RF energy

Gradient magnetic fields

Conclusion Hemodynamic support devices (IBP, RV / LV assist devices) Absolute contraindications to MR examination

Hemodynamic support devices (IBP, RV / LV assist devices)

Absolute contraindications to MR examination

Conclusion ICDs and pacemakers Relative contraindications to MRI

ICDs and pacemakers

Relative contraindications to MRI

Conclusion For most devices, if there is good clinical indication for MRI scan, then benefits probably outweigh the risks American Heart Association American College of Cardiology North American Society for Cardiac Imaging Society for Cardiovascular Magnetic Resonance

For most devices, if there is good clinical indication for MRI scan, then benefits probably outweigh the risks

American Heart Association

American College of Cardiology

North American Society for Cardiac Imaging

Society for Cardiovascular Magnetic Resonance

Journal source Levine GN, Gomes AS, Arai AE, et al. Safety of magnetic resonance imaging in patients with cardiovascular devices. Circulation 2007 doi: 10.1161 / CIRCULATION AHA.107.187256 New Statement on Safety of MRI With CV Devices. URL: http://www.medscape.com/viewarticle/566881

Levine GN, Gomes AS, Arai AE, et al. Safety of magnetic resonance imaging in patients with cardiovascular devices. Circulation 2007 doi: 10.1161 / CIRCULATION AHA.107.187256

New Statement on Safety of MRI With CV Devices. URL: http://www.medscape.com/viewarticle/566881

Addendum Next 15 slides give some examples of cardiovascular devices that are implanted in patients. The images have been culled from various sources, which are obvious from the caption, where relevant. This is meant as an APPENDIX to the main presentation.

Next 15 slides give some examples of cardiovascular devices that are implanted in patients.

The images have been culled from various sources, which are obvious from the caption, where relevant.

This is meant as an APPENDIX to the main presentation.

Coronary stent

Coronary stent – Drug eluting

PTCA stent – Enlarged view

Peripheral stent

Aortic stent-graft

Tornado ® Embolization coil

Gunther-Tulip IVC filter

IVC Filter – University of Texas Health Science Centre

Heart valve – TTK Chitra

Annuloplasty ring

Septal occluder

Loop recorder

Implantable Cardioverter Defibrillator

Intra-aortic balloon catheter

Ventricular assist device