Safety And Clinical Impact Of MRI In Patients With Non–MRI-Conditional Cardiac Devices – OpEd

In 1996, this writer came across an instance in which physicians with the help of modern medical technology saved a life in an emergency.  We were in Chennai in one of the premier cancer hospitals in India to attend a conference. On the second day, one of our colleagues was found unconscious in his room. The physician who examined him suspected that it is possibly an instance of brain haemorrhage. Within a few hours he underwent many tests including digital subtraction angiography in a specialty hospital. 

He underwent surgery to place an aneurysm clip in his brain. He came back to normal health within a few weeks.  A few months ago, he suffered from some neurological issues. His physicians decided against an MRI scan because of the uncertainty regarding the nature of the clip. If the clip is made of some Ferro-magnetic material it can cause severe adverse events. Fortunately, his physician could managed his condition by medication. 

A study published in Radiology: Cardiothoracic Imaging (Vol 2 Issue 5, 2020) Journal showed that doctors can perform MRI examinations safely in patients with non MRI compatible cardiac devices, including those which are pace-maker dependent or have abandoned magnetic leads in their body.

Researchers led by Dr. Sanjaya Gupta, Department of Cardiology, Saint Luke’s Mid-America Heart Institute, Kansas City, Missouri, say that in the USA over two million people have cardiovascular implantable electronic devices (CIEDs), including pacemakers and implantable cardioverter defibrillators (ICDs); and half of these patients are predicted to eventually require an MRI examination.

“The U.S. Food and Drug Administration (FDA) has identified a subset of implanted cardiac devices as MR conditional, meaning they pose no known hazard under specified conditions. Pacemakers or ICDs that have not met the criteria are considered non-MR conditional. In these patients, clinicians are forced to choose between removing a necessary cardiac device or getting an alternate and potentially less-effective imaging test.”, a press release from the Radiological Society of North America said.

MRI study not to be done in some cases

Specialists discourage MRI studies or prohibited MRI use in many of these people over fears that the powerful magnet of the scanner will heat the metal in the devices, potentially damaging heart tissue and harming the devices. It can also create other equally severe adverse effects because of the force the magnetic field can exert on the devices.

The researchers revealed that although there are an increasing number of patients with MRI-conditional CIEDs, a large number of patients implanted with non–MRI-conditional CIEDs could not undergo an MRI until March 2011, when a change to Centers for Medicare and Medicaid Services National Coverage Determination was granted to allow coverage for MRI examinations in prospective registries designed to assess the risk of MRI examinations in this population.

The researchers found that three groups of patients (ie, thoracic MRI examinations, pacemaker-dependent ICDs, and abandoned leads) that were not included in many previous studies represent an important segment of patients who often require MRI examinations for clinical reasons

A new patient registry

At their institution, the researchers created an institutional review

board–approved registry (Patient Registry of Magnetic Resonance Imaging in Non-Approved Devices [PROMeNADe]),with a protocol  similar to those previously published   but also including thoracic MRI examinations, pacemaker-dependent patients with ICDs, and abandoned leads.

The objective of this registry was to determine the safety and clinical utility of performing MRI examinations, including thoracic examinations, in participants who have non–MRI-conditional CIEDs and by including participants who were pacemaker dependent and those with abandoned leads. 

According to Dr Gupta while all devices implanted in patients today are MRI compatible, millions of people worldwide, including many young people, have older devices considered not compatible. 

“It’s unfair to tell these people that they can’t get an MRI for the rest of their lives.” He said in the RSNA press release.

Exclusion of cardiac MRI studies or patients with fractured leads

Prior research has demonstrated the safety of performing MRI exams in patients with non-MR conditional devices. However, those studies did not account for pacemaker-dependent ICD patients, or patients whose hearts won’t function if the defibrillator is removed or stops working. Other groups not accounted for in previous studies include patients undergoing chest and cardiac MRI exams and patients with abandoned or fractured leads, or wires that connect the device to the heart.

The present study, precautionary steps

The researchers prospectively enrolled 532 participants (211 women) with a mean age of 69 years from September 2015 to June 2019, and underwent a total of 608 MRI examinations (61 cardiac MRI examinations in the PROMeNADe registry. All participants had device interrogations performed before and after each MRI. Pacemaker-dependent patients received asynchronous pacing.  The researchers took special precautions. 

Specialists performed all examinations with hemodynamic monitoring in the presence of an Advanced Cardiovascular Life Support–certified electrophysiology nurse. Two nurses, each with more than20 years of clinical experience, also assessed the patient for any symptoms of chest pain or burning, near syncope, or Palpitations during the examination, or for changes in vital Signs (eg. heart rate, blood pressure, and oxygen saturation).

A physician was immediately available to attend to any possible emergency but was not physically present in the MRI suite. After each study, a complete device interrogation was performed, followed by reprogramming back to original device settings. All participants had follow-up in a device clinic within 3–4 months after the examination, either via remote download or in-clinic check

Patients had their devices checked before and after each MRI and had their vital signs monitored closely by a nurse during their time in the scanner. Devices were turned to asynchronous mode in pacemaker-dependent patients before they went in the scanner. ICD patients had tachycardia therapies disabled during the MRI.

Results 

The break-up of the group was: Cardiac devices including pacemakers formed the major group (46%), ICDs (30%), cardiac resynchronization therapy (CRT) pacemakers (4%), and CRT defibrillators (17%), as well as abandoned leads (2%). 

Pacemaker-dependent patients comprised 27% of all MRI examinations. There were no patient- or device-related complications. 

An important feature of the study was that the researchers carried out a survey of the physicians who had referred the patients for the MRI study. These physicians underscored the importance of the exams.

One hundred and fifty out of 348 (43%) completed the clinical utility surveys of MRI examinations. 

The survey revealed that these MRI examinations changed the suspected diagnosis 25% of the time and changed suspected prognosis in 26% of participants, with planned medical or surgical treatment being changed 42% of the time.

The results demonstrated that MRI exams—including chest MRI exams—can be performed safely in pacemaker-dependent ICD patients and in patients with non-MR conditional devices or abandoned leads.   

The registry is now the largest series of MRI scans that has ever been put together in patients with pacemaker-dependent ICDs. It is also the second largest in patients with abandoned or fractured leads and the third largest in non-compatible devices.

Physicians’ expectations

Dr Gupta stated that they are hopeful that this work will add support to expand the FDA’s indications for devices that are considered MRI-compatible.

“This registry demonstrates that MRI examinations, including thoracic MRI examinations, can be performed safely in patients who have non–MRI-conditional devices, in pacemaker-dependent patients with ICDs, and in patients with abandoned leads.

These MRI examinations can have a substantial impact on patient care, justifying the extensive resources used to perform them.” the researchers concluded.

A paper titled “Contraindications to magnetic resonance imaging” by Dr T. Dill in heart.bmj.com refers to many factors to be considered before an MRI study.The link: https://www.rad.pitt.edu/sites/rad_docs/mrrc-docs/ContraindicationsMRI.pdf

The recent paper refers to only heating effects. Are the other factors not relevant while considering non MRI conditional Cardiac devices?

 “We discuss several potential adverse effects of MR non-conditional devices, including potential heating of leads and device components, rise in threshold, premature battery depletion and device reset, among others.  Heating of leads and device components is not programmable and is inherent to the device itself.  We looked for heating and all of the other potential issues listed above and we did not find any evidence of these adverse effects. We listed it in one of the tables in the paper”, Dr. Sanjaya Gupta responded to this writer’s e mail query

The researchers attempt to collect feedback from the physicians who referred the patients for MRI study was appropriate, particularly in light of the criticism that medical imaging is overused.  Sadly, only 43% (150/348) responded to your survey. Why did 57% not respond?

Is it fair if I say that busy physicians may not be interested in the final utility of such surveys?

Dr Gupta responded thus:

“If you look at the literature involving surveys, many studies quote response rates about 40 – 50% are not uncommon.  In our study, we found a response rate of 43% and we were pleased with this amount. Busy clinicians often just don’t have time to fill out surveys.  I’m sure more people found it valuable but just didn’t have time to respond.”  

Presently, specialists can carry out MRI studies of all patients if the hospital is equipped to handle them safely by following the necessary protocols