MRI IN CARDIAC PACEMAKERS

Magnetic resonance imaging (MRI) is a widely accepted tool for the diagnosis of a variety of diseases. However, due to safety reasons the presence of an implanted cardiac pacemaker or of an implantable cardioverter defibrillator (ICD) is considered to be a strict contraindication to MRI in most medical centers. Thus, a substantial number of patients are precluded from the diagnostic advantages of this imaging modality. Because of its high spatial and contrast resolution, it is now the primary diagnostic imaging test of choice for disorders of the central nervous and musculoskeletal systems. It is also important for oncological and certain cardiovascular disorders. In certain clinical instances, denying a patient an MRI procedure may have a significant effect on the patient’s care. Subsequently, this could prove to have a major impact on overall public health.

Cardiac MRI imaging is performed to:

• evaluate the anatomy and function of the heart, valves, major vessels, and surrounding structures (such as the surrounding pericardial sac).
• diagnose a variety of cardiovascular (heart and/or blood vessel) problems.
• detect and evaluate the effects of coronary artery disease.
• plan a patient's treatment for cardiovascular problems and monitor a patient's progress over time.
• evaluate the anatomy of the heart and blood vessels in children with congenital cardiovascular disease.

Physicians can use use cardiac MRI: 

• examine the size of the heart chambers and the thickness of the heart wall.
• determine the extent of myocardial (heart muscle) damage caused by a heart attack or progressive heart disease.
• detect the buildup of plaque and blockages in blood vessels.
• assess a patient's recovery following treatment. 
• assess the heart anatomy, muscle function, heart valve function and vascular blood flow both before and after surgical repair of congenital cardiovascular disease in children.

Benefits

• MRI is a noninvasive imaging technique that does not involve exposure to ionizing radiation.
• MRI images of the heart are generally clearer than with some other imaging methods for certain conditions. This advantage makes MRI an invaluable tool in early diagnosis and evaluation of certain cardiac abnormalities, especially those involving the heart muscle.
• MRI has proven valuable in diagnosing a broad range of conditions, including cardiac anatomical anomalies (e.g., congenital defects), functional abnormalities (e.g., valve failure), tumors and conditions related to decreased blood flow.
• MRI can help physicians evaluate both the structure of an organ and how it is working.
• MRI enables the discovery of abnormalities that might be obscured by bone with other imaging methods.
• The contrast material used in MRI exams is less likely to produce an allergic reaction than the iodine-based contrast materials used for conventional x-rays and CT scanning.
• Cardiac MRI allows physicians to examine the structures and function of the heart and major vessels without risks like exposure to radiation typically associated with traditional, more invasive procedures.

Risks

• The MRI examination poses almost no risk to the average patient when appropriate safety guidelines are followed.
• If sedation is used there are risks of excessive sedation. The technologist or nurse monitors your vital signs to minimize this risk.
• Although the strong magnetic field is not harmful in itself, implanted medical devices that contain metal may malfunction or cause problems during an MRI exam.
• There is a very slight risk of an allergic reaction if contrast material is injected. Such reactions usually are mild and easily controlled by medication. If you experience allergic symptoms, a radiologist or other physician will be available for immediate assistance.
• Nephrogenic systemic fibrosis is currently a recognized, but rare, complication of MRI believed to be caused by the injection of high doses of gadolinium contrast material in patients with very poor kidney function.

Although there is no reason to believe that magnetic resonance imaging harms the fetus, pregnant women usually are advised not to have an MRI exam unless medically necessary. Acquiring detailed images of the coronary arteries and their branches is more difficult with MRI than with cardiac CT or invasive coronary angiography.
MRI typically costs more and may take more time to perform than other imaging modalities.


Thanking for reading 
Akshaya Srikanth,
Pharm.D Internee
India