Cardiac Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) uses a strong magnetic field, radio waves and a computer program to provide remarkably clear and detailed pictures of internal organs and tissues. It does not use ionizing radiation (x-ray) and iodinated contrast agent/dye.

Some MRI examinations may require you to receive an injection of contrast material into the bloodstream. The contrast material most commonly used for an MRI exam contains a metal called gadolinium. It is far less common for a patient to have an allergy to a gadolinium-based contrast agent used for MRI than the iodinecontaining contrast for CT. However, even in such a case, it may still be possible to use it after appropriate premedication, a simple process called desensitization.
The procedure is valuable in diagnosing a broad range of conditions in all parts of the body, including heart and vascular disease. Cardiovascular MRI (CMR) is specialized MRI of the heart and vascular system. It requires specialized equipment and expertise.
It is used to detect or monitor cardiac disease and to evaluate the heart’s anatomy and function in patients with congenital heart disease. Cardiac MRI may provide images of the heart that are better than other imaging methods for certain conditions. It can provide still images, amazing videos of the heart and valve function, evaluation of cardiac and valvular function parameters, and information on myocardium, myocardial perfusion, pericardium and cardiac thrombus and mass. It is valuable in differential diagnosis between myocardial infarction and myocarditis, pericarditis or infiltrative diseases of the heart. It also provides very informative 3-dimentional imaging for left atria mapping and pulmonary vein ablation.

Regarding various implanted metallic materials or electrical devices in the heart, thoracic and cardiac MRI can be performed safely using a magnetic field intensity up to 3 tesla in patients with:

  • coronary stents,
  • steel sternal wires,
  • titanium vascular clips,
  • Peripheral vascular stents,
  • Peripheral vascular stent grafts (like that used to treat aortic aneurysms),
  • nitinol materials and devices,
  • patent ductus arteriosus, atrial septal defect, ventricular septal defect occluders, and patent foramen ovale closure devices,
  • left atrial appendage closure devices,
  • annuloplasty rings,
  • biological prosthetic heart valves,
  • mechanical prosthetic heart valves produced after 2000 (bileaflet pyrolytic carbon valves).

In any case and prior to undergoing an MRI, inform your doctor or MRI technologist that you have an implant, and show them the device implant card. Regarding valves produced before 2000 or pacemakers and implantable cardioverter-defibrillator devices, as well as in any doubt, you need to look for the MRI compatibility in the labeling supplied with each product or contact your implanting doctor.

Patients with implanted electrical cardiac devices have long been advised to avoid MRI because of the potential for adverse effects. Certain cardiac devices that have been proved to pose no such hazards have been designated by the Food and Drug Administration as “MRI conditional.” However, millions of patients worldwide have devices that are not MRI conditional, and at least half of these patients are predicted to require an MRI during their lifetimes. In these patients who had implanted non–MRI-conditional pacemakers or cardioverter-defibrillators (ICDs), nonthoracic MRI at 1.5 tesla is safe, as long as they follow a specific safety protocol before and after the imaging procedure (N Engl J Med 2017;376:755-64).