A pacemaker is a small metal, electrical device which is inserted into the chest. It is used to treat arrhythmias (abnormal heart rhythms), for example if the heart beats too slowly, known as bradycardia.
Some pacemakers (biventricular) help the chambers beat in sync and can treat heart failure. Another type of metal cardiac device is an implantable cardioverter defibrillator (ICD), these are used to treat patients who have had, or are at risk of life-threatening arrhythmias.
The way they work is to deliver a shock to the heart and return it to a normal rhythm if it beats too quickly or in an abnormal way. Most of the time patients with pacemakers or ICDs do not notice the device and live normal lives. Issues can arise, however, if they require an MRI scan.
As MRI scans use strong magnetic fields they can disrupt and damage metal devices such as pacemakers. Historically, having a pacemaker was a clear contraindication to having an MRI scan, however newer devices are MRI compatible, and some research has shown that even older devices are safe.
Magnetic resonance imaging (MRI) uses strong magnetic fields and radio waves to produce detailed internal images of the body. It is a non-invasive imaging test and gives information on various structures including organs, muscles, bones and blood vessels.
An MRI machine is a large, tube-shaped structure which can look like a narrow tunnel. Prior to the scan your clinician will ask you to complete a safety questionnaire to check for any contraindications, if safe to proceed the scan will be arranged. Read on to find out what happens during an MRI scan.
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As discussed, MRI scans use strong magnetic fields and radio waves to produce detailed internal images of the body. Unlike X-rays and CT scans, MRI scans do not use ionizing radiation. That does not mean, however, that they come without risks.
The strong magnetic fields can heat the metal pacemaker, damaging the heart tissue or modifying the pacemaker's settings. Subsequently in patients with pacemakers or other implantable cardiac devices, MRI scans have been discouraged or prohibited, and alternative, often less effective, imaging techniques are used.
Due to an increasing number of individuals with pacemakers or ICDs, research has been carried out to better understand the risk associated with MRI scans. This is particularly relevant due to the increasing use of MRI scans in diagnostic medicine as well as for screening. In the United States over 2 million people have cardiovascular implantable electronic devices, this encompasses pacemakers and ICDs. It has been predicted that half of these patients will eventually require an MRI.
The US Food and Drug Administration (FDA) has identified a select group of ICDs as not posing a hazard under specified conditions, known as “MR conditional”. Pacemakers and ICDs which do not fit these criteria are known as non-MR conditional.
There is growing evidence that MRI scans can be performed safely in patients with non-MR conditional pacemakers and ICDs. The Radiological Society of North America conducted a study of over 500 patients and concluded that MRI scans can be performed safely in pacemaker-dependent ICD patients and in patients with non-MRI conditional devices or abandoned leads.
A systematic review and meta-analysis also confirmed the safety of MRI scanning in patients with non-conditional cardiac implantable electronic devices (CIED). It must be noted, however, that a strict selection and monitoring protocol needs to be utilised. This involves device evaluation and peri-procedure programming and close patient monitoring during the scan.
This requires experienced personal as well as significant time investment. In many studies the MRI procedure was supervised by cardiac technicians who are experienced in device programming as well as cardiac nurses or a cardiologist who are trained in advanced cardiac life support.
In summary, for these scans to be performed safely in patients with CIEDs there needs to be significant care and time taken to ensure the correct protocol is followed. For Ezra, patient safety is an absolute priority, and we will refer you to discuss any potential interference from metal objects such as pacemakers with your MRI technologist.
Producing MRI compatible devices without the need for interrogation, monitoring or programming is the ultimate goal with the hope that patients with cardiac devices can be assured of their safety during an MRI scan in the future.
Depending on the part of your body which needs to be scanned, there are alternative options to an MRI.
CT scans are often used, these use ionizing radiation instead of magnetic fields and therefore patients with metal devices are safe. CT scans create images of bones and soft tissues, however; they are not as effective as an MRI at differentiating subtle differences between soft tissue. Learn more about tests and imaging techniques which are used to test for cancer.
Ultrasound is also an imaging modality which is safe for patients with pacemakers. Ultimately, it is up to the treating physician to decide which scan is most appropriate in the context of the clinical picture.
It is important to discuss the issue with a clinician before proceeding with any scan. Such decisions are made on a risk/benefit basis. The benefit of an MRI may outweigh the perceived risks if it can be performed under the correct protocol.
Historically patients with a pacemaker were not able to get MRI scans due to the risk of damaging the device or surrounding tissue. Fortunately, due to evolving technology most new pacemakers and ICDs are now MRI compatible.
Many individuals, however, have older devices that are deemed non-MR conditional. There has been promising evidence which demonstrates that MRI scans can be performed safely in patients with these devices, but strict protocols and monitoring is required.
If an MRI is recommended and you have a pacemaker or ICD it is important that your physician is aware so they can assess if it is a compatible device. Additionally, if you have had one recently inserted you will need to wait a period of time prior to the scan. Be sure to consult your healthcare provider.
Ezra does not currently recommend a full-body screening MRI for individuals with pacemakers. For those without such devices, however, it is a safe, non-invasive imaging modality which gives information on over 13 different organs. Changes could be detected and treated before they become symptomatic or problematic, so be proactive about your health and consider booking a scan today.
