Haojie Wang, MD, PhD, FACC, RPVI, Specialty in Clinical Cardiology, Medical Director of the Cardiovascular MRI lab at Hospital Baylor Scott & White Heart and Vascular in Dallas, talks about the improvements in cardiac MRI technology and understanding the risks/benefits associated with patients who have implanted pacemakers.
Interview conducted by Ivanhoe Broadcast News in November 2018.
You are the director of the lab?
Dr. Wang: Yes
For the most part, is this what you do? Do you do MRIs to investigate things about the heart?
Dr. Wang: The main thing I do here is multi-modality cardiac imaging, with cardiac MRI being the most powerful diagnostic tool. I have been in practice for more than six years following my fellowship training. I’ve been interpreting echocardiograms, cardiovascular CTs, nuclear stress tests, peripheral vascular ultrasound studies, and performing interventional transesophageal echocardiograms. In the last two to three years, I have been heavily involved in the Center for Valve Disorders here at Baylor Scott & White Heart and Vascular Hospital – Dallas and part of the valve implantation team. We evaluate patients with significant valvular issues, like aortic stenosis and mitral regurgitation, as a team including cardiac surgeons, interventional cardiologists, and imaging cardiologists. I am very excited that now we are able to perform high-quality cardiac MRI studies to help our patients. We use MRI to assess the sizes of the heart chambers, strength of the heart muscle, leaking or stenotic heart valves, blood flow in the heart muscle, and scar tissues in the heart.
What kind of a breakthrough has this been? With all the advancements in imaging and things that you can do, what’s it doing for the field?
Dr. Wang: With cardiac MRI we can see more things we couldn’t see before with other imaging modalities; we can see the heart in much better resolution and more details. For this case, the patient had several cardiac imaging studies done already, but the diagnosis was still elusive. As a result, he was referred here for a cardiac MRI. Out of this study, we were able to clarify and make the final diagnosis, which was not previously sought.
Right and you had some complications because he had a pacemaker?
Dr. Wang: He had a pacemaker with a legacy, older lead. He was initially scheduled to have the cardiac MRI per protocol for patients with a conditional pacemaker. A conditional device means it’s safe to have an MRI with specified conditions of use. He did have a conditional generator and a conditional lead to the right ventricle. However, the atrial lead, which is the lead going to the top chamber on the right side, was non-conditional and put him at potential risk for the MRI study. We had to accommodate the study for his legacy device. Historically, a legacy device was a contraindication for an MRI study. However, because now we know more about the effects on pacemakers and defibrillators in specific MRI environments from several recent major clinical studies, early this year, the Centers for Medicare & Medicaid Services (CMS) approved patients getting MRI studies with non-conditional or legacy devices.
Right so this is just recently approved? This technique? And not only that, but you also made some adjustments in the power of the magnet in the MRI?
Dr. Wang: Absolutely. There are specific criteria for patients getting the MRI. Those conditions pre-specify certain perimeters: what the strength of the main magnet should be, how strong the static magnetic field could be, how fast we can change the magnetic field strengths, and how much energy we could put into the patient, etc.
Part of that is because this is an older version of a pacemaker, right? Does that contribute to it?
Dr. Wang: Certainly. The atrial lead was the lead in question, which was not MRI conditional and considered to be unsafe to be scanned. Now the newer models are MRI conditional. That means it’s safe to have an MRI with specified conditions of use.
So, his problem was specific to him and other patients who had those older pacemakers?
Dr. Wang: Right, and this is great news for patients who have the older devices. We are very excited to provide care for those patients in a safe manner and are still able to provide greater diagnostic MR images by minimizing the artifacts generated by the devices and leads during MRI.
And because you can do these more complete or better images with MRI, and you develop new protocols for those older pacemakers, you can help more people?
Dr. Wang: I believe we can help a lot of people who have the older pacemakers, defibrillators or other implanted devices. About three quarters of them could need some MRI studies over their lifetime.
Three quarters of them? And previously they couldn’t get it?
Dr. Wang: Right, they couldn’t. They were turned away from an optimal imaging test because having these older devices was a contraindication. The MRI was not advisable for these patients until recently.
Tell us what the perceived danger might be if you’ve got metal in your body and you’ve got these incredibly strong magnets. What is the fear?
Dr. Wang: The fear is that MRI’s strong magnetic field could interfere with the functionality of the pacemaker or the defibrillator. For patients with a pacemaker, the strong magnetic field and high frequency electromagnetic waves could interfere with the pacemaker’s pacing function. This could put the patient in danger because their heart rate could go dangerously slow if the patient is pacemaker-dependent and the pacemaker stops working. Too strong radio waves could cause some tissue heating, as well.
Any chance that the magnet could actually rip the device out of the body?
Dr. Wang: That theoretical fear is unfounded. There are no reports any device has been ripped off.
It never happened?
Dr. Wang: No, and very few patients have ever felt the torqueing force on their device generator.
So, it could potentially ruin the effectiveness of the pacemaker!
Dr. Wang: For a patient with a defibrillator it is a different story because the defibrillator is trying to watch for tachyarrhythmias, or the rapid heartbeats. If the defibrillator detects the alternating magnetic field as the patient having rapid heartbeats in the scanner, it will try to protect the patient and could try to shock the patient out of the “dangerous arrhythmia”. That would cause serious complications.
This new development is a combination of things, right? It is new materials used in pacemakers and defibrillators combined with a better understanding and more controls of the MRI machine? With the magnets?
Dr. Wang: Right. The magnet strength basically has stayed the same. However, we know more about the safety of the MRI environments for patients with pacemakers and defibrillators. Now that we know what is safe, what the limits are and what level the magnet strength should not go beyond, basically all the devices could be scanned as long as they meet the specific requirements.
Any idea how many lives will be saved because of this new development?
Dr. Wang: It is in a very early stage, so we do not know. We did not expect that Mr. Unclebach had this condition nor did his outpatient cardiologist and electrophysiologist. So now we know more about his heart, he got the correct diagnosis and received appropriate changes in his management plan. I think time will tell how much impact we will have on patients’ lives and management, and I believe will be very significant.
What do you anticipate? How many people have these conditions perhaps that result in death that you might pick up something that might prolong their lives or maybe save them to live a full and complete life?
Dr. Wang: Optimal diagnostic imaging with cardiac MRI could provide invaluable diagnostic and prognostic information in helping patients get the best care they need. I believe the value will translate into longer and healthier lives in many patients.
For example, with cardiac MRI, we can visualize and quantify the scar tissue in the heart muscle. Numerous studies have shown the more scar tissue in the heart like our patient has, the higher the risk of sudden cardiac death from a fatal arrhythmia as well as higher risk of congestive heart failure or heart attacks, etc. It could be an important piece of information to take into consideration when assessing an individual’s candidacy for a life-saving defibrillator.
Is this what you would consider a medical breakthrough?
Dr. Wang: I think it is a medical breakthrough because we could scan patients with conditional devices as well as legacy devices. For patients with legacy devices – the patients that have the older devices or older leads that are not MRI conditional – they were denied the opportunity to have an MRI in the past, which could be crucial in their diagnostic work up.
There’s a certain population that many of them have already lived out their lives and you don’t know how many of them had something that you couldn’t see before?
Dr. Wang: Right. Many patients are still living with the legacy devices even though the newer devices are MRI conditional. These patients with legacy devices and legacy leads will benefit from cardiac MRIs. With cardiac MRI, we have better image resolution and higher diagnostic confidence to clarify and nail the diagnosis. That, I believe, is the best way to achieve a higher quality of care and lower cost. Getting the diagnosis right would eliminate other unnecessary testing.
MRI is a multi-modality imaging tool in itself. We can look at the morphology and function of the heart, we can quantify the blood flow in the heart and the blood flowing across the big blood vessels or valves, and quantify the severity of the leaking valve. In addition, we can perform stress testing with cardiac MRI to check for any signs of blockage in the arteries in the heart. We can visualize and quantify the scar tissue to see how much damage is already done in the heart and predict future events
There’s no effort or movement to remove the legacy pacemakers from all the people who have them right?
Dr. Wang: The procedures to extract the legacy leads and devices are not risk-free, so it is reserved for patients with device malfunction or infection.
In the patient’s case they did extract it?
Dr. Wang: Because of the high-risk features on his cardiac MRI scan, his pacemaker system was upgraded to a defibrillator. He did get his legacy lead extracted during the same procedure, since it was put in not too long ago.
So, it is not the new MRI technology that makes the MRI scans safer for patients with legacy devices?
Dr. Wang: Correct. For the patient with a legacy device to receive a cardiac MRI, it’s not the advancement of the MRI technology per se that made it possible. It’s because we know more about the safety and the risks of patients with these devices getting MRIs. We know how to control the MRI environment and adjust the device settings to make sure it’s safe. That’s why we’re very proud here at Baylor Scott & White Heart and Vascular Hospital – Dallas. We have a dedicated team, including imaging cardiologists, MRI technologists, registered nurses, and electrophysiologists working closely together to make it safer for the patients.
END OF INTERVIEW
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