33. Cardiac MRI with Dr. Deborah Kwon

worldwide cardiovascular disease affects the lives of hundreds of millions dedicated cardio nerds everywhere are working hard to fight this global epidemic these are their stories

Welcome back, CardioNerds. We've got a great topic to cover today. We have touched on the incredible diagnostic power of cardiac MRI during several of our episodes, such as hypertrophic cardiomyopathy, cardiac amyloid, and our heart failure series. Well, it's time to get down and nerdy with the subject so we can help start to develop an understanding and appreciation for this modality and how it applies to cardiology.

And friends, for this journey into the world of protons and magnetism, we are incredibly honored to learn all about cardiac MRI from a personal mentor and director of CMR at the Cleveland Clinic, Dr. Debbie Kwan. For the technically inclined, we begin real nerdy with some basic principles and physics of CMR before getting into the strengths and caveats for this powerful modality.

Then about halfway through, we discuss some illustrative cases from the CardioNerds Clinic to learn how cardiac MRI can be helpful for specific pathologies hitting all of the main cardiac failures we keep referring to. Coronary failure, myocardial. valvular, electrical, and pericardial. In short, in this episode, we take you from the protons to the bedside. So buckle up for a tremendous discussion. It might get a little bumpy. Yeehaw! I am very excited.

Before we jump in, I just wanted to plug a non-cardiology podcast called Mental Filter, a great podcast that views all aspects of life through the lens of mental health. hosted by cognitive behavioral therapist Shmuel Fishler. I joined him for a two-part episode series to discuss many aspects and coping mechanisms that may be helpful to others as one progresses through the many stages of medical education from pre-med to fellowship and beyond.

We'll share the links to these episodes in the show description. Definitely worth a listen. Wow, Dan, that sounds like such an incredible show with an important theme. Shmuel, wherever you are, thanks for putting this together. And CardioNerds, an episode on cardiac imaging would not be complete if we didn't talk about the brand new cardiac imaging education platform, Cardiac Imaging Agora, taking the field by storm. It was founded and produced by Dr. Alicia Gemelli.

and a personal mentor, Dr. Whale Jaber. They produce bite-sized videos with illustrative images to explain basic and advanced concepts in all imaging modalities, useful for the beginner and advanced alike. Definitely check it out and see the link in the episode's description below.

Lastly, the show is growing beyond our wildest dreams. Thanks to all of you. If you haven't already, please take a couple seconds to rate and review us on your favorite podcast platforms and spread the word to your colleagues, mentors, and protégés and help us spread the cardigan.

nerd movement all over the world. And just remember, this podcast is not meant to be used for medical advice. The views expressed here do not necessarily reflect the opinions or policies of our employers. The goal is to simply enjoy learning more about cardiology from our favorite cardio nerd experts. Welcome back, CardioNerds. We are so excited for today's episode because Dan, Corrine, and myself get to learn all about a tool that I don't think I ever really truly appreciated, the cardiac MRI.

And friends, you're in for a real treat because we will learn directly from an expert among experts, Dr. Debbie Kwan, the Director of Cardiac MRI here at the Cleveland Clinic. But before we dive in, I'd like to introduce a very special guest who will be joining us in the fun, Dr. Nicole Pristera.

Nicole completed medical school at Case Western, an internal medicine residency at Duke. She is now an all-star first-year cardiology fellow. I have so many stories I'd like to share about her, but I think it's more meaningful coming from two individuals who've had tremendous influence on her career. Dr. Amy Zoss, Duke's famous residency program director, said the following about Nicole.

Nicole is a total superstar. I remember working with her when she was an intern on general medicine. She was so capable and always thinking a few steps ahead and could back up her decisions with great clinical reasoning. She continued as an outstanding upper-level resident, and none of us were surprised when she had her choice of fellowship programs.

Our program director here, Dr. Venu Menon, said that I knew Nicole was special when we recruited her in the first place, and that's become even more evident now. Nicole has been just a spectacular fellow and simply extraordinary in every way. I expect her to be a leader in cardiovascular.

medicine in the future. Nicole, it's such a pleasure to have you on the show. Thanks, Amit. Thank you for such a kind introduction. I have been so fortunate in my training to come across such incredible mentors with Dr. Zas and now with Dr. Menon. And on that note, I'm very honored today to introduce Dr. Debbie Kwan. She attended medical school at the University of Michigan and internal medicine residency at University of Pennsylvania.

She then completed her general cardiology and cardiovascular imaging fellowships here at the Cleveland Clinic. Dr. Kwan is really our go-to for all things cardiac MRI. She is the director of cardiac MRI and serves as the core lab director for NIH. More personally, Dr. Kwan and Amit are part of my coaching family, and I'm also very excited to be Dr. Kwan's Continuity Fellow for the next two years. Dr. Kwan, welcome to the show.

Thank you so much. I'm super excited to be part of the Cardio Nerds podcast and also to be able to be sharing this time with both you and Amit. Thank you so much for the invitation. Thanks, Dr. Kwan. Dr. Quan, what actually pulled you towards the dark side to go into cardiac MRI? Yeah, I think, so I... just seeing the cardiac MRI images. I was floored. I'm like, oh my gosh, here's echo. And then here's MRI. I can see so much.

That's a really good question. I think it's just to be the ability to be able to see the disease is what really fascinated me. The ability to see tissue characterization. understand the properties of the myocardium and being able to help guide therapy from that aspect. It's what made my heart flutter. Like seeing the images is what made my heart flutter. And then being able to describe that to the patient.

is what really fascinated me. Oh, thank you for sharing that. That was fantastic. You know, when it comes to understanding hypertrophic cardiomyopathy, I feel like I'm a good bonafide cardio nerds level. Just listen to our episodes. But when it comes to cardiac MRI, I feel like I'm at about a college level. So maybe you could help us out and just give us a basic intro to cardiac MRI principles, how you would explain it to a first year cardiology fellow. Sure.

Just to preface that, to be honest, I think it takes an entire lifetime to fully understand CMR principles. And after being in the field for over 10 years, I still feel like I haven't fully grasped all the concepts. A CMR principles will always be a continuity of learning throughout the years. But just to begin, I thought maybe I would start off with a comparison with echocardiography, since I think that's...

very easily graspable for most cardiology fellows. So if we think about a cardiac ultrasound, it uses high frequency sound waves to create images. The ultrasound beam passes through fluid and less dense tissue, but the sound waves bounce off or reverberate off of bones or dust or tissue like the myocardium. And then the ultrasound machine uses these reverberated sounds to create the images.

However, with cardiac MRI, magnetization and radiofrequency signals are used to excite protons or hydrogen atoms, and images are created by the different signals that are produced by these protons. So to simplify things, you really need three components to produce a magnetic resonance image. First, you need to have an object with lots of hydrogen atoms.

And fortunately, the human body is made up of about two-thirds of water, and that has a high density of lots of protons or hydrogen atoms. And then you also need a strong magnetic field, such as an MR scanner. And then you need radiofrequency waves. So to give a little background, a typical clinical cardiac MRI scanner is usually 1.5 Tesla or 3 Tesla.

And to give you an idea of how strong those magnetic fields are, let's put them in relation to a refrigerator magnet or the Earth's magnetic field. So a refrigerator magnet is about 100 Gauss. And by the way, one Tesla equals 10,000 Gauss. And the Earth's magnetic field is about half a Gauss. So a 1.5 T magnet is 15,000 Gauss or 150 times the strength of a refrigerator magnet. Whereas a 3T magnet is 30,000 Gauss or 300 times the strength of a refrigerator magnet.

So that helps to give a little bit of scope of how powerful these clinical cardiac MRI scanners are. And then the third thing that you would need is radiofrequency waves, which the cardiac MR scanner provides to help develop some of these signals. So I don't know if anyone listening to the podcast has ever seen an MRI scanner before. Probably you all have. But for those who haven't, it looks like a giant elongated donut called the boar.

So the patient enters the bore through the opening of the MR scanner or this elongated donut hole. And inside the bore are the main magnetic coils. And it's these coils that create the main magnetic field. Just awed by the amount of science and technology that we utilize every day but take for granted. Yes, yes, it's pretty amazing. So how are the images created?

As I mentioned, you can think of a hydrogen atom as a proton, and protons all have certain spin properties, and these spin properties can be manipulated. So you can think of a proton as a spinning top, and when you spin the top... It spins very fast in the right to left axis, and that spinning motion keeps it upright. But as it loses its kinetic energy and the frequency slows down, you can start to see it wobbling around the vertical axis.

And that wobbling motion or rotation around the vertical axis can be referred to as precession. And one of the main MRI principles is that the frequency of that precession or that wobbling. is directly related to the strength of the magnetic field. So with magnetic resonance imaging, think of the organ of interest as a lattice of many different spinning protons.

And these protons are all oriented in all different directions and held together by different strengths of the bonds based on their environment and different protein contents. And when the body enters the bore of an MRI scanner... All of the spinning protons are magnetized such that their orientations mostly align with the direction of the magnet. So now we're ready to apply the radiofrequency pulses to create the signal that can be transformed into an image.

So maybe I can make another analogy. Think of the protons as soldiers in an army barrack before bedtime. Some of the soldiers will be laying down and some of the other soldiers may be sitting on the side of their beds talking. Some other soldiers might be gathered in the corner playing a game of cards.

And then imagine that a trumpet is blown and all the soldiers have to get in bed as the lights are turned out. This is analogous to the protons entering into the bore of an MRI scanner. All the soldiers are now horizontal in their beds.

Now think of the magnetic excitation radio frequency pulse as a sergeant walking into the barracks in the middle of the night. So when the radio frequency pulse is applied, or when the sergeant enters the room, All the soldiers suddenly become upright and run to the foot of the bed with their hands held up in salute.

However, once the sergeant leaves the barracks, the soldiers will want to return to bed, and the amount of energy that's expended for the soldiers returning to their original position in bed is analogous to the T1 relaxation time. So the energy that's released when the proton relaxes from a high energy. state that's flipped into a certain orientation, just like the upright soldier in salute. And as it relaxes down to its lower energy state, which is the soldier laying back down, back in bed.

this energy can be released, picked up by the receiver coil and transformed into an imaging signal. Does that make sense? Yeah, totally. I really love the analogies, Dr. Kwai. It sounds like... We can get 300 refrigerators, a bunch of spin tops, a radio frequency tower, and an army, or we can just go to the basement and use an MRI. Yes, that's right. I'll choose the MRI.

That's great. Yeah, I felt like having some illustrations might be helpful instead of just thinking of protons spinning. Yeah, super helpful. And Dr. Kwan, just to make sure I understand it right, at baseline. protons have all different sorts of spins. We apply a magnetic field and align them along the magnetic field that's applied from the borer.

And then we give them a radio frequency pulse, and this energy is absorbed. And as they absorb the energy, they alter their spin. Correct. And then when we stop applying this energy force, the spin... of the protons realign with the magnetic field from the bore, and protons in different tissues will release this energy and realign with the magnetic field at different rates. And the speed at which they realign with the magnetic field in releasing this energy is the T1 relaxation time. Correct.

And then there's something called the T2 relaxation. And this is, again, we could go back to the analogy of a spinning top. So how fast the protons are spinning. as I mentioned, or this precessional, the wobbling is directly proportional to the strength of the magnetic field. So when an RF pulse is applied,

energy is absorbed and the wobbling rate or the precession of the protons are now exactly identical, or most of the protons are spinning at the same rate. And then they're thought to be in phase. However, when the RF pulse is removed, the uniformity of the wobbling starts to decay such that each proton's precession rate slightly differs from the other proton's wobbling rate. And this loss of uniformity of...

precession or wobbliness is referred to as the T2 relaxation. So we're flipping protons and the orientation of the proton and the relaxation of that. orientation is T1. And then the relaxation or the decay to randomness of the precession rate is the T2 decay. Interesting. And so... protons in different tissues will have different properties in terms of how they release these energies. And the difference is what we use to develop the MRI contrast to see different tissues. Correct.

A lot of the tissue contrast that we see with CINE imaging, for instance, is without the use of contrast because there's different water content in the blood versus the water content within the myocardium. creates the differences in this contrast and signal between the blood and the myocardium. All right, that's very helpful.

Dr. Kwan, that was an amazing summary. And thanks for really shedding light on such a complex topic and also just like really highlighting how complex cardiac MRI is. So just taking us back to super basics with cardiac MRI, we know from, you know, medical... school and everything that every test has.

risks and the benefits. And one of the things beautiful about MRI seems like there's not really a lot of risk except the buzzword of NSF, which is nephrogenic systemic fibrosis, which is a concern with renal dysfunction and the gadolinium. So do you mind talking? a little bit about that and what's the reality of that risk and who should we really avoid gadolinium exposure in? Sure, sure. Yes. So nephrogenic sclerosing fibrosis is a very important and dangerous potential.

adverse event that can happen with gadolinium administration. And because of that, the FDA restricted the use of gadolinium in patients with chronic and acute kidney disease with GFR less than 30 in 2006. And since then, there's been a drastic reduction in the cases of NSF. And we also have learned that the prior cases of NSF seem to be highly related to the type of gadolinium agent that was used. And the vast majority of these previous NSF cases were associated with Omniscan or gattodiamide.

And the second highest number were associated with magnavis or gadopentate. And these two contrast agents are no longer really used in clinical practice. So therefore, the incidence of NSF has been extremely low. And recent data have shown that if you use... a group 2 gadolinium-based contrast agent, the risk of NSF is extremely low. And as a result, the American and the European radiology guidelines have been recently updated to liberalize the use of gadolinium agents based.

renal function. Also, a recent meta-analysis published in 2019 in JAMA of close to 5,000 patients. suggested that the risk of NSF from group 2 gadolinium agents in patients with stage 4 and 5 chronic kidney disease is less than 1%. So this meta-analysis helped to support the recent change in guidelines. So if your hospital center is using a group 2 gadolinium-based contrast agent,

We know function no longer needs to be screened prior to gadolinium administration. And even patients who are on dialysis can get gadolinium, but they have to undergo dialysis as soon as possible, preferably within 24 hours. So currently, there's no strong indication to restrict gadolinium from patients with severe kidney disease if you're going to be using a group 2 agent.

However, gadolinium administration in the setting of acute renal failure in patients whose renal function has not yet plateaued is not recommended. Now, in regards to concerns around gadolinium, I think the concern that's recently become more of concern...

is this observation that gadolinium can accumulate in the brain for patients who've had repeated contrast-enhanced studies. It appears that gadolinium accumulation is likely dose-dependent and can start to accumulate after four contrast studies. It's not really known what clinical implications are associated with gadolinium accumulation because we've been doing gadolinium contrast enhanced MRIs in patients for over 30 years. And this was mostly seen in patients who have...

neurologic disease who undergo contrast brain MRIs frequently. But nonetheless, because of this observation, the FDA strongly advises the judicious use of gadolinium. And the field of CMR has been... evolving to try to see if we can develop techniques that no longer require gadolinium administration, particularly for tissue characterization. And I do believe that we may be able to develop techniques that no longer need gadolinium potentially in the near future.

That's incredible and so clinically relevant. I feel like the recommendation there has changed so much since I started residency. Yeah, it was just within the past, I think 2018 or 2019 is when they changed the guidelines. Amazing. It's incredible how much information you can actually get from a cardiac MRI. And it's a wonder why CMR isn't really the imaging modality of choice for everyone. What are some of the challenges or...

caveats to know about. We talked a little bit about the renal function, but what else do you usually take into account? Yes, I agree that while CMR provides real treasure trove of information, there's definitely limitations. So cardiac MRI is never going to replace echocardiography in my mind because... echocardiography has a real strength in the sense that it's a bedside examination. Despite all of the technical advances, I'm not sure we'll ever be able to develop a bedside cardiac MRI scanner.

And also the temporal resolution for echocardiography is superior to cardiac MRI currently. But there's also some misconceptions about cardiac MRI. So some people think that cardiac MRI is extremely long in terms of how long the exam takes. And a focused clinical cardiac MRI scan really can take about 30 to 40 minutes, which is actually very similar to the length of a comprehensive echocardiogram. However, there will be longer protocols, such as a congenital CMR, and those typically take...

60 minutes or even longer. And the fact that CMR is usually available only in academic centers or main hospital centers, a lot of these centers are also doing... cardiac MR research. And so some of these scans may be longer because they're also tacking on some research protocols on top of it. But if you are doing a purely focused clinical CMR...

exam, that could typically be done in about 30 to 40 minutes. Wow, that's a really great point. When you compare CMR to echo, the scan time really isn't that long, especially for the more simpler protocols. But Dr. Kwan, what about getting the patient through the scan in terms of their comfort? In regards to patient tolerability, the patient has to be able to hold their breath for about 10 to 12 seconds at a time. They have to be able to hold still.

And they have to lay flat. So this has important implications, particularly in patients who are admitted for decompensated heart failure. So doing a cardiac MR scan and someone in decompensated heart failure will not provide. great quality images because these patients obviously can't hold their breath very long and they can't lay flat and they also get tired. Their breath holds start to become shallower as the exam gets longer because they're obviously in heart failure.

So for inpatients, it's advisable if the CMR needs to be done during that hospitalizations because it's going to dictate their management. You should really wait till the volume status is optimized. so that the patient can be able to lay flat and do good quality breath holding. In regards to claustrophobia, about 10% of patients referred for cardiac MRI have an issue with claustrophobia.

And anxiolytic therapy with sublingual alprazolam is highly effective. I would say that up to 80% of patients who have claustrophobia can successfully complete their CMR study if they're given some kind of anxiolytic therapy. But it is important to ask patients before sending them for cardiac MR if they have claustrophobia and to ask patients if they're willing to proceed because sometimes just the anxiety of coming down and not knowing that they were going to have to undergo.

this test further exacerbates their claustrophobia and anxiety. So definitely it's advisable to have that discussion with patients beforehand.

Sounds like there are some real caveats to taking a patient down for a cardiac MRI, but also a lot of misconceptions in that we may at times overplay our hesitation for ordering an indicated scan. What do you think about CMR in patients with implanted electrical devices like pacemakers and ICDs? In regards to ICDs and pacemakers, there are definitely certain medical devices like cochlear implants or insulin pumps that have absolute...

contraindications for cardiac MRI. MRI techs are very vigilant about making sure that patients don't have devices that are contraindicated for undergoing MRI. However, in regards to implanted cardiac devices, there are conditional devices and then there's non-conditional devices. So non-conditional devices used to be absolute contraindication for cardiac MR, but this recently has been... revised. There was a recent New England Journal of Medicine paper.

that evaluated over 1,500 patients, which was published in 2017. And it demonstrated really reassuring safety for performing cardiac MR in patients with non-conditional devices. None of them had any significant long-term complications. Now, that being said, the comforts of the radiologists or cardiologists who are performing CMR to allow this to be done in patients with non-conditional devices is variable.

Some centers will allow it to be done, and some centers are not comfortable performing them. Scanning patients with devices requires a significant amount of coordination of efforts. Definitely those things have to be taken into coordination because it takes more scheduling to put these patients on our CMR schedule. And then the other thing to also be cognizant of is even though we can do the CMR. study safely, the image quality is another thing to consider. So patients who have devices that are

directly on top of their heart are more likely to have non-diagnostic images because the device generator creates a lot of artifact, which we call susceptibility artifact. And it basically looks like a big black hole. So the farther away the heart is from the device, the more likely you'll be able to have better quality images. So it's important to look at the chest x-ray to see how close the cardiac chambers are to the device.

But then there's also specialized sequences that can help minimize these artifacts. And so it'd be important to have local expertise to be able to optimize protocols for these patients. Okay, so MRI scan time, patient tolerability. and the presence of cardiac devices are not prohibitive for obtaining a cardiac MRI. But Dr. Kwan, what about the cost? In terms of cost, there's a lot of misconception, I think, in terms of...

the fact that CMR is astronomically more expensive than echocardiography. And it really depends on the insurance provider. So if you... took Medicare, for instance, I recently looked up the comparative cost. So a transthoracic echocardiogram is reimbursed at a rate of $210. based on the 2019 Medicare reimbursement rate. And then a multi-planar SPECT is reimbursed at $559. A cardiac MRI with and without contrast is reimbursed at $433.

And a stress cardiac MRI is reimbursed at $513. So if you actually compare stress MRI with stress nuclear, stress MRI is cheaper. It is twice as expensive as a... trans thoracic echocardiogram, but it's not astronomically more expensive. So those are things that have to be taken into consideration, obviously, is that the indication for cardiac MR, you really have to be able to say that.

what you're wanting to see is beyond what echo can provide. If an echo has already been acquired and has given you good quality images that you're happy with. And then the other thing to take into consideration is the heart rate and rhythm. So the patient has to have a heart rate that's regular and that's not too fast. So if a patient is having frequent ectopy, for instance, that's going to make it very difficult to be able to gait and have a high quality study.

And if the patient's heart rate is too fast, like above 100, that's also going to make it difficult. We have been scanning some patients with atrial fibrillation as long as their irregular rhythm is not significantly irregular. When that happens, again, the gating has issues and it's not high quality. Dr. Kwan, going back to safety.

For these patients who have cardiac devices and when we go to consent them to discuss the risks and benefits of MRI, can you talk a little bit about what the specific risks are to the patient? What should we be discussing with them? Yeah, so there can be heating of the device that can cause some local injury, but recent studies have suggested that that local injury usually is not clinically impactful.

And that New England Journal of Medicine paper did look at the effect on the device itself. Sometimes it can affect the programming mode. One case was reset to VVI pacing and could not be reprogrammed. So the device had to... be replaced. But in regards to the ability to sense and pace, the thresholds and the sensitivity were not significantly impacted. But as part of the consenting process, I think we still have to be able to relate to the patient that there's a small risk that these...

thresholds could be altered when the device is put into a high magnetic field. Thanks for going over that, Dr. Kwan. And I just want to give a shout out that 2017 practice changing energy and paper that really made us much more comfortable. in getting MRIs in patients with these implantable devices is out of a group from Hopkins with PI Henry Halperin, who Dan is actually doing research with. So it's very exciting to see that. Yeah, they've really pioneered the field.

It's amazing. I mean, we've been citing Hopkins all the time and saying, well, they're doing it and, you know, look at what they're able to do and the advances they've made. So yeah, you guys have really been the pioneers. Yeah, I'm actually more in the resuscitation arm of the lab, but they are working a lot on device therapy, like ablation therapies with using cardiac MRI real time. So that's what they're doing. Yeah, you guys have a interventional MR scanner, I believe.

Yes. Yeah. Everything in the lab gets designed to be MRI compatible. So like our ECMO machines are all MRI compatible. Oh, wow. Yeah. That's awesome. Dan uses that when he cannulates pigs on ECMO. Yeah. Okay. Anyways.

Yeah, Dr. Kwan, this is like super valuable, especially, you know, when we, you know, sometimes you get complacent, you're in the clinic and you're just like clicking boxes and you're like, oh, I'll get the cardiac MRI. And what you realize is like, it's a whole consultation process and one click and epic and a signature.

actually setting forth such a big, you know, scheduling events. And also you really have to go through all this with the patient. So when you're considering getting an MRI or specifically cardiac MRI, I have always been thinking about, you know, you get... anatomical data, you get functional data, and you get this beautiful buzzword that we call tissue characterization. That seems to be a big benefit for cardiac MRI.

over some of the other modalities. Dr. Kwan, do you mind recapping on these different aspects of cardiac MRI that we get to help our patients? Yeah, so the basic clinical sequences for cardiac MRI include anatomic or morphologic assessment, and this can typically be helpful for patients who have dilated.

aortas and you want to be able to measure and quantify the size. Sydney imaging can be used to assess myocardial function and that's really one of the main strengths of cardiac MR because it's the gold standard for quantifying ventricular size. and function because it's able to assess it in a three-dimensional acquisition as opposed to making assumptions that echocardiography does when you do a two-plane and a four-plane assessment.

And then we can do perfusion imaging to assess for myocardial ischemia and also to quantify myocardial blood flow. Tissue characterization, as Dan mentioned, is really one of the highlights of cardiac MR, and it is able to assess tissue properties. to identify presence of myocardial edema, myocardial fibrosis, infiltrative processes, and assess and quantify the size of myocardial infarct.

And some sequences require gadolinium for tissue characterization, and some do not. So T2 imaging helps to assess the presence of edema or inflammation, and that does not require gadolinium administration to acquire that data. Flow velocity quantification is also extremely useful, and it's used to measure the amount and direction of flow, which is typically performed at the proximal aorta.

and can also be performed at the main pulmonary artery. When you do both the proximal aorta and the pulmonary artery, then you can quantify. the QPQS. Flow velocity quantification can be used to quantify valvular dysfunction. So you can quantify aortic regurgitation, pulmonic regurgitation, and then you can integrate that with the volumetric assessment from your CINE image.

to derive and quantify mitral regurgent volume infraction as well as tricuspid regurgent volume infraction if you've acquired a pulmonic flow velocity assessment. And then the last major protocol is 3D whole heart imaging or MRA imaging, and that allows you to get a full volume set of data, and then you can reconstruct it. This can be useful for aortas, but also for congenital.

abnormalities if you want to be able to look at different structures or different shunts or surgical repairs and reconstruct them in a three-dimensional nature. So those are the main components of the cardiac MR. And it's also important to realize that we don't perform all of these sequences in every patient because that would take an exorbitant amount of time, which would also be uncomfortable for the patient.

So cardiac MRI studies are really tailored to the clinical question and the indication at hand. And we have standardized protocols based on these common indications. So for instance, if you have a patient where you just wanted to look at their aorta.

We would do the MRA and the 3D whole heart imaging, but we wouldn't do tissue characterization if there was no concern for myocardial infarct or some kind of underlying cardiomyopathy. And then on the flip side, if you're sending somebody for... cardiomyopathy assessment, we would not necessarily be doing 3D whole heart imaging to look at the aorta.

Because again, it adds extra time in it. If it's not clinically useful, we don't do that. So when you place a cardiac MRI, it's important to indicate what the clinical question is so that the study is protocoled correctly. So public service announcement for everyone, what you write in the comments really matters. Yes. So Dr. Kwan, thank you so much. This was such an incredible intro to cardiac MRI. But now let's get to the heart of cardiac MRI. Oh, God. By going over some case examples.

Maybe you can walk us through how a cardiac MRI could be helpful in some of the patients we saw in a cardiac nurse clinic yesterday. Karine, take it away. Absolutely. So I'll start with the first patient. Ruth Hanna, who's a 45-year-old G1P1 female with prior preeclampsia and anterior STEMI status post in LAD STEM three years ago, who's now being seen for chest pain.

TTE shows an EF of 45% with mid-apical anterior hypokinesis, as well as an apical aneurysm. How does CMR help delineate ischemic heart disease? Yes, that's a great question and a great case example. So cardiac MR would be very useful for delineating the ejection fraction in this patient. Sometimes with echocardiography, the apical images can be foreshortened to provide a falsely elevated ejection fraction.

In patients with ischemic heart disease, particularly that are on that borderline of 35%, if you're not sure if they might need to be referred for primary prevention, cardiac MR is really good for giving you a gold standard assessment of the ejection fraction. In terms of... Risk stratification, cardiac MR would be really important for also assessing the LV size. And if this was in the acute setting, looking for microvascular obstruction can also help to identify higher risk patients.

In this particular patient who has an apical aneurysm, cardiac MR is very helpful for also identifying the presence of an LV thrombus, which would be important to identify because obviously then this patient would need to be put on anticoagulation. And then because this patient is now coming in for chest pain, if you opted to go for a non-invasive way of assessing for myocardial ischemia.

a stress MRI could also be obtained to assess myocardial blood flow. Oh, and then obviously the strength of Cardiac MR is also the ability that it can assess the presence of myocardial infarction, the size of the infarct, and underlying viability of the myocardium.

What a powerful tool. And, you know, just thinking about this case, I'm struck by how young she is. But then I remember that Dr. Martha Gulati taught us that adverse pregnancy outcomes are an important atherosclerosis risk factor for women. So this patient had a history of preeclampsia.

Speaking of which, so she did have a stress MRI and it showed an anteroapical perfusion defect and apical aneurysm with a mural thrombus with associated late gadolinium enhancement corresponding to scar. On further review, however, her chest pain is sharp. pleuritic, and worsens with recumbency. EKG on follow-up shows diffuse ST elevations and PR depression, except in AVR, which showed ST depression and PR elevation. ESR and CRP are moderately elevated. Dr. Kwan.

How is CMR helpful for pericardial disease? That's a great question. So cardiac MR is actually very useful for pericardial disease, particular with pericarditis. Cardiac MR can provide assessment of... pericardial inflammation and also can assess for the presence and size of pericardial fusion. So on our first images with cardiac MR, we can also look for pericardial thickness, and that could be your first cue to pericardial disease.

Then we do T2-STIR imaging, which looks for pericardial edema. And that helps us to discern if this is acute versus subacute versus chronic. So if it's enhancing on the T2 stir images, that suggests that the pericarditis is more in the acute phase. And then we can also do free breathing sequence that helps to delineate if there's constrictive physiology.

So basically, it's another way to assess for interventricular dependence. So we ask the patient to take deep breaths in and out, and we can visualize simultaneous RV and LV filling.

So if the patient has constrictive physiology, you'll see the RV septum flattening or bowing to the left during inspiration to accommodate the venous return. So in patients who have really significant... pericarditis with a significant amount of pericardial inflammation, they can also develop constrictive physiology, which can resolve as inflammation resolves with anti-inflammatory medication.

So it is important to assess for constrictive physiology in these patients with acute pericarditis. And then the delayed enhancement assessment can be utilized to also assess the degree and severity of pericardial inflammation. So basically, these patients with pericarditis can develop neovascularization of their pericardium, and that's how the gadolinium gets into the pericardial tissue.

And because gadolinium is an extracellular agent, the gadolinium stays in the pericardium and that enhances when we do the delayed imaging. So this allows us to do tissue characterization of the pericardium. And this can be tracked with patients who have... pretty complex pericarditis that's not responding well to therapy. We've shown from our center that cardiac MRI can help dictate.

the intensity of anti-inflammatory medication that needs to be utilized. So if a patient has severe concentric... pericardial enhancement on delayed enhancement imaging, then these patients probably should be treated with triple therapy out of the gate with NSAIDs, colchicine, and prednisone.

And this is because we've shown that people who have severe pericardial enhancement are more likely to have recurrence. And we think it's probably because they were not adequately treated initially to address the degree of inflammation. You know, that's great. You mentioned that Nicole and I were just talking about the use of serial cardiac MRIs in Dr. Klein's clinic in managing complex patients with recrudescent pericarditis. Yes, those are very challenging patients to manage.

Cardiac MR can be useful in those patients who are refractory to medication therapy. Oh, definitely. Yeah, it's definitely fascinating to hear how you can use MRI as almost a titrating test to see if your dose is adequate or inadequate. You almost think, I mean, prior to now, now I'm well informed.

But I, you know, you think of like an MRI is like, what do I have? Do I have severe AR? You know, some sort of like a snapshot in time. And then I won't get another MRI forever. You know, this is quite interesting. And side note, we, Amit and I and Kareen and... Heather are dying to do a pericarditis F cardio nerds episode. It's on our wish list. So we'll return to this subject for sure. Alan Klein would be a great person for that podcast.

It's been mentioned. It's been mentioned. We're on it, doctor. It's really like kind of been on our wish list since we started. We keep like having to move it back because of other things.

Okay, let's talk about Susan Kidds, who is a 35-year-old woman athlete who is admitted after a VF arrest that occurred during a tennis match. Thankfully, she received immediate bystander CPR with early defibrillation and... prompt Rosk. She has had prior syncope during training and an uncle who died suddenly at the age of 40. Resting ECG shows incomplete right bundle branch block, right precordial T wave inversions, and an epsilon wave in V1 through V3.

On telly, she's had multiple runs of NSVT, of a left bundle branch block morphology, and echo shows pretty impressive RV dilatation. A heart failure consult is done to consider endomyocardial biopsy, but request CMR beforehand. What are we thinking about here and how would cardiac MRI help us? Yeah, so based on the clinical and pertinent findings, I think at the top of the differential would be ARVC and CMR definitely helps to provide further.

delineation of that by assessing the right ventricular size and function and also ability to assess for regional right ventricular wall motion abnormalities as well as areas of dyskinesia. Cardiac MR can also look for areas of phatofibro infiltration of the RV. And so you can assess for tissue characterization, if you will, of the RV to help delineate that entity. However, it should be mentioned that the task force criteria for CMR is really for ARVC is really just based on the presence of.

RV size and function and regional wall motion abnormalities. They did take out the RV tissue characterization, I think in 2010, because they thought that there was a lot of false positives that were being identified. It's really helpful to note that CMR is so useful in right-sided disease, especially for imaging the right ventricle.

which is such a complex three-dimensional structure that is difficult to really understand on echocardiography. Yeah, by echocardiography, we often call it the forgotten ventricle. And we don't have as much dedicated assessment with echo. Yes. In our show, we've talked about cardiac amyloid. We've done hypertrophic cardiomyopathy.

And we did in general kind of an evaluation of heart failure, especially non-ischemic cardiomyopathies. And we've definitely touched on the importance of this modality and in those conditions. So that's great. Yeah.

All right, moving on to our next case, we have Ben Adams, a 28-year-old man with no past medical history who presents with progressive dyspnea during his routine morning runs. His exam is notable for an early diastolic decrescendo murmur that is best heard at end expiration while leaning forward. While concentrating on the murmur, you also notice a subtle rhythmic head bobbing.

His echo shows eccentric aortic insufficiency and a dilated left ventricle, but further characterization is limited. Dr. Kwan, how is cardiac MRI helpful for the evaluation of valvular heart disease? Yes, that's a really great question. So CMR can be extremely useful for the assessment of valvular heart disease, particularly in patients with aortic regurgitation.

So CMR can help to identify the aortic valve morphology. And in a young 28-year-old man, you would be suspecting that he has a bicuspid or a unicuspid aortic valve. And so the cardiac MR can help you identify the presence of a bicuspid valve and then also to assess if there's concomitant aortic pathology, such as a dilated or aneurysmal ascending aorta. So CMR has great utility for those components.

But in addition to that, aortic regurgitation can sometimes be somewhat difficult to accurately quantify by echocardiography, especially when the JET is eccentric, as in this case. And so cardiac MR can be helpful because it can provide quantitative measurement of both the aortic regurgent volume as well as the regurgent fraction. And similarly, cardiac MR can assess for holodiastolic flow reversal.

as can be done with echocardiography. And this has been shown to help be a very useful arbitrator of those with hemodynamically significant versus non-significant aortic regurgitation. And finally, in this patient who's asymptomatic, who has, it sounds like, significant regurgitation based on the physical exam. The main question would be to see if he meets surgical criteria based on the LV size and...

function of the left ventricle. So again, since cardiac MR is the gold standard for LV size and function, it would be able to provide very robust measurements. of the ejection fraction as well as LV diameters and the LV volumes to help you discern if this patient should be referred for surgical evaluation.

Yeah, that was perfect. So in our patient on his cardiac MRI, he was actually found to have many of the features that you described. He has a bicuspid aortic valve, a thoracic aortic aneurysm, as well as moderate left ventricular dilation. Wait, was he referred for surgery? In the hypothetical Cardi Nerds Hospital, he will be. I love it. Dr. Roselli's all over it. And the OR the next day. There you go.

So our next patient, Ms. Holly Massey, is a 55-year-old woman with subacute fevers, chills, and night sweats who's now presenting with an acute ischemic left leg pain. Auscultation reveals a mild diastolic plop and echo is limited by poor sonographic windows, but there's a nondescript echo density in the left atrium. What's the role of CMR in the setting of cardiac masses? Yes, another great question.

CMR can be helpful in the role of cardiac masses, but certain features should be taken into consideration. So if the cardiac mass is small and if it's high frequency, meaning that it's moving around quite a bit, then TEE might be a better option. So for patients who have suspected endocarditis, for instance, TE spatial resolution is 0.6 to 1 millimeter, whereas CMR is 2 to 3 millimeter. So my rule of thumb usually is that I don't really recommend CMR unless the mass of in question.

is one centimeter or larger, because I'm not confident that we would be able to see the mass that well by CMR if it's smaller than that. And so such masses that are one centimeter or smaller should really be better evaluated with TEE. However, in larger masses, such as in this case, which is highly suggestive for a myxoma, CMR can be helpful in terms of delineating the size, where it's attached.

But it should be mentioned that while CMR can be helpful in terms of tissue characterization, it shouldn't be thought of to be diagnostic of the etiology of the mass. histopathology will always be required for definitive diagnosis. Where I think CMR can be helpful is if you're worried about the mass potentially being a neoplasm.

and you wanted to see if the mass was infiltrating tissue planes or if there was satellite lesions that are also within the cardiac structures, then cardiac MR could be helpful. But masses can sometimes be difficult to discern if you should get a TEE or a CT scan or cardiac MR. And so sometimes having a discussion with a... cardiac imager would be very helpful to delineate the next best advanced imaging test. Thank you, Dr. Kwan.

So we are actually in the middle of a myocarditis series where we're building out basically a whole structure for everyone to kind of get on the same page in terms of myocarditis. And we had... a real patient actually joined us last week, Chaz Miller, who's actually, we did his case from the medical perspective in episode 31. And then in 32, he came in, his wife, Julie gave, they just gave us a really, really.

great appreciation for what they went through during their whole process. So anyways, he presented with cardiogenic shock and heart block and was found to have full-minute myocarditis. He was... pretty sick when he came in and he really was not able to undergo cardiac MRI. But how would cardiac MRI have helped in a case of myocarditis? Yeah, that's great. I'm definitely gonna have to listen to that, those episodes.

So patients who are in hemodynamic extremis, as you mentioned, obviously are not suitable for CMR. So patients who are in heart block, if they have a temporary pacemaker wire, they can't go for CMR because those are contraindicated. But if the patient's stabilized and you want to be able to further characterize the extent of their myocarditis, I think CMR can be particularly helpful. And I think it can be particularly helpful in patients who have...

positive cardiac enzymes, EKG changes, normal coronaries, and you're not yet sure if they have myocarditis. Because CMR can delineate the presence of myocarditis, pericarditis, myopericarditis. or Takotsubos, or differentiate that from myocardial infarction and the setting of an epicardial coronary thrombus that has recanalized by the time of a coronary angiography that was thus not appreciated and then said that it was normal coronaries.

because late gadolinium enhancement would be characteristic of a myocardial infarct, these patients would then be realized that they had an ischemic event as opposed to myocarditis. But in patients with... proven myocarditis, whether it's by biopsy or whatever it means, I still think that CMR has an important role to play because it can help predict the prognosis of the patients.

So it can assess the degree of left and right ventricular dysfunction. And also the degree of late gadolinium enhancement has been shown in several studies to be associated with long-term risk. And so there's been a couple of studies that demonstrated that people who have late gadolinium enhancement basically doubles the risk of major adverse cardiovascular events during long-term follow-up. And so these patients should be followed more closely.

Also, not only just the presence of late gadolinium enhancement, but also the pattern and location of the gadolinium enhancement. So mid-wall enhancement or Apache distribution. seemed to have an even higher risk. And those patients had close to a threefold increased risk in MACE. So I do think that doing CMR in these patients will help risk stratify patients, help physicians.

discern optimization of their medical therapy and determine the closeness of follow-up. Basically, if a patient has myocarditis and they have a normal CMR exam, obviously those patients are going to be much more lower risk. But I do want to highlight the fact that recently CMR has become much more quantitative. And so we're doing T1 and T2 mapping. And sometimes patients can have negative late gadolinium enhancement.

but abnormal T1 and T2 times. And these patients would be diagnosed by myocarditis based on T1 and T2 imaging as opposed to by late gadolinium enhancement alone. Oh, wow. That was very helpful. Actually, I had been reading that when we were prepping for the myocarditis series. We definitely saw that that has been popping up in the literature, this quantification. So that is very, very helpful.

Yeah. In an older study, I think it was a JAP 2012 paper, it was over 200 biopsy-proven myocarditis patients. And in that study, about 50% of patients had late gadolinian enhancement. So if you refer a patient for CMR and they say no late gadolinium enhancement seen, that doesn't rule out the presence of myocarditis. T1 and T2 mapping really should be performed. That helps to improve the sensitivity of the assessment.

I wonder if in the future, this will also be able to predict who will end up having a dilated cardiomyopathy from the episode of myocarditis. Yes. Yeah, I think that's a great point. So that would be a very strong hypothesis to suspect that those are the ones that are higher likelihood of developing dilated cardiomyopathy down the road.

Dr. Kwan, that was such a helpful discussion. I feel so much better about the role of cardiac MRI in the assessment of cardiovascular disease. Well, thank you so much for the opportunity. This was a lot of fun. Dr. Kwan, we can't thank you enough for taking the time to teach us today. And, you know, I also want to add that Dr. Brian Griffin, who is the section head of imaging here, said the following. Debbie is the epitome of the triple threat physician scientist.

She has really enhanced cardiac MRI by developing a database and has spearheaded our use of machine learning in cardiac MRI applications. She is a talented inventor and clinician and just submitted her first R01. As such an accomplished physician, scientist, mentor, educator, and mother, we have to ask, how do you do it all? Do you have any advice for us as we launch into our careers? Oh, that's a great question.

I think that definitely it cannot be done alone. So having a strong social and emotional network is definitely key. And mentorship is... the most impactful thing I would have to say. I was lucky enough to have Dr. Wilson Tang as my mentor in fellowship. And I actually wanted to go into heart failure, but then I was pulled to the dark side. and went into cardiac imaging. But he has remained my mentor throughout the years. And I never thought I would submit my own R1, honestly.

But he kept pushing me. And this past year, I... Actually, looking back, I can't believe I actually submitted it. Congratulations, Dr. Kwan. Thank you. We'll see. It's in the revision mode. But if it actually gets funded, it's going to be all thanks to Wilson. So I think... my advice is to definitely seek out supportive mentors. There's a ton of people out there. And the other thing I think is that mentorship is a very strong bi-directional relationship. I think sometimes...

We feel bad approaching mentors because we think we're taking away their time. But I've been fortunate to now serve as a mentor. to trainees and it's it's really inspiring and invigorating it's um it's a it's definitely a bi-directional process and it really helps to get back to the vision of why we went into medicine and science. It's really to further understand disease and better serve our patients. And then the other really important thing is to find very understanding and

forgiving and a serving spouse. Definitely could not have done it without a husband. We can all relate to that. Dr. Kwan, you are such an example for us fellows. And, you know, I really just want to thank you for one being you and also for letting us borrow a part of your vacation day on a Friday evening to spend time with us cardio nerds.

I highly enjoyed it. And I just wanted to say that what you guys are doing is amazing. It's really so much fun. And I see a phenomenal future ahead for the cardio nerds. So thank you for touching so many lives. Thank you. Thank you. Oh my God. My heart's fluttering.

Well, that brings us to the end of our show. So it's time to make like an S2 and split. You can follow us on Twitter at CardioNerds and please share what made your heart flutter this week. Send us a clip to CardioNerds at gmail.com. If you enjoyed the show, be a nerd and spread the word. And now, a Flutter Moment.

Hi, cardio nerds. My name is Aroma Shahid. I'm an international medical graduate currently studying for US MLEs. My husband and I listen to your podcast regularly. They're very knowledgeable.

So, um, what makes my heart flutter? So during one of my rotations, I remember recognizing a classic ASD fixed split in the pulmonic area. And that was the first time I was able to apply all my theoretical knowledge into real patient care. And that made my heart flutter thank you so much for the show keep up the good work guys