Melanie Cole, MS (Host): Welcome to UF Health MedEd Cast with UF Health Shands Hospital. I'm Melanie Cole. And we have a panel for you today with two University of Florida College of Medicine physicians highlighting new treatment options for inappropriate sinus tachycardia. Joining me is Dr. Kevin Xiang, he's an Assistant Professor of Cardiology and Electrophysiology; and Dr. Thomas Beaver, he's the Chief and Professor in the Division of Cardiovascular Surgery.

Doctors, thank you so much for joining us today. Dr. Xiang, I'd like to start with you. Give us a working definition of inappropriate sinus tachycardia and tell us a little bit about the pathophysiology of it.

Kun “Kevin” Xiang, MD, PhD: Inappropriate sinus tachycardia is a clinical syndrome characterized by a patient that has a sinus heart rate that's always above 100 beats per minute at rest, or have a monitored study showing average heart rate more than 90 beats per minute. Those patients usually with fast heart rate come with a variety of symptoms such as palpitations, they can feel dizzy, chest pressure. Sometimes the symptoms can be debilitating, severely affecting patient's lives and functions.

Melanie Cole, MS: Well, Dr. Xiang, how do you differentiate this from other forms of tachycardia? What makes it so different?

Kun “Kevin” Xiang, MD, PhD: The key is for inappropriate sinus tachycardia, the patient has a fast heart rate all the time. It's like they're running a marathon 24/7. Other types of tachycardia, patient heart rate goes up and down, depends on the situation. So, that's the key differences between this diagnosis and other tachycardia diagnosis.

Melanie Cole, MS: But sticking with you for just a second, Dr. Xiang, what is the current diagnostic criteria? How are you identifying it? When patients come to you, whether it's from primary care or internal medicine, what diagnostic criteria are you using?

Kun “Kevin” Xiang, MD, PhD: We usually do a resting EKG to show patient has a heart rate more than 100 beats per minute, or we can do a Holter monitor for at least 24 hours. And the average heart rate during the monitored study period needs to be above 90 beats per minute. This also has to be associated with clinical symptoms, that's how we diagnose inappropriate sinus tachycardia.

Melanie Cole, MS: Dr. Beaver, why don't you start by some of the limitations of current treatments? And we're going to get into this hybrid treatment, but what are some of the primary challenges in managing IST, particularly in patients as we're going to talk about with refractory symptoms?

Thomas Beaver, MD, MPH: Thank you, Melanie. And the limitations of current treatment is a lot of times with the current medical therapy, including beta blockers or diltiazam or other calcium channel blocker class of family, patients will try them and then they still have the persistent heart rate or the dose is required to get an effective treatment end up leaving them with significant side effects of fatigue, they don't tolerate the medications.

There's a more recent medication that has been effective named ivabradine, and Kevin can comment on it more, that has been effective in some patients. But even then, after a while in some patients, the efficacy decreases. It's also very expensive, and sometimes the patients have trouble with insurance companies trying to get coverage for that treatment. So at that point, Kevin can comment about ablation in more detail as he is an electrophysiologist.

But one of the challenges with catheter ablation has been the phrenic nerve runs in proximity to the atrium where what we call the sinoatrial node or the SA node is located. And using catheter approaches, there's often stimulation of the phrenic nerve that can even be damaged from the ablation. So, that's actually how I got involved with this probably over 15, 20 years ago because they had asked me as a surgeon is there a way to port access thoracoscopy to pull the phrenic nerve away from the catheter areas so that ablation can be formed, and could you do epicardial ablation? And we actually had done that. We have our own series published, including about 15, 20 patients. We've done more since then. But certainly, we can do it effectively with a thoracoscope.

And so, what we call a hybrid therapy is when we use surgical and this is minimally invasive, port access surgery, combined with the cardiology catheter mapping techniques and that's we call a hybrid approach. So, that's how as surgeon I became involved with this therapy. But as Kevin mentioned, these patients have often been through multiple medications, multiple sometimes ablations, and they come to our office with an inability to go to school, inability to hold down a job, and it can be a very distressing situation, as you can imagine, for the patients.

Kun “Kevin” Xiang, MD, PhD: Yeah. I concur what Dr. Beaver has just said. So, the current treatment for IST is very limited. Pharmacological therapy is still the first line. But the choice of medication is limited by the effectiveness. Also, a lot of patients cannot tolerate medical therapy. In the past 30 years, the radiofrequency ablation by catheters also has been studied and explored, but there are a lot of limitations including the potential complication for damaging the phrenic nerve and recurrence of tachycardia after ablation. Sometimes people end up getting a pacemaker, because of a permanent damage to the sinus node. The catheter-delivered ablation is in general not recommended unless this patient failed for other therapies. That's why this new hybrid sinus node-sparing ablation is very promising. We can let Dr. Beaver comment more on this new technology.

Thomas Beaver, MD, MPH: Yes. Thanks, Kevin. The concept here is, you know, I think in medical school, we always thought the SA node was kind of like a tip of a pencil and it was in the top of the atrium where the superior vena cava meets the right atrial junction. But what we've learned over the last few years, and particularly as I've been involved with this therapy over the last few years-- I think Kevin would agree-- it's more like a peanut shape. I mean, it can be a longish structure. And to try to pinpoint ablate, oftentimes you'll need to ablate the superior aspect. And then, typically, what happens is the SA node will reset itself a little lower, and then you have to reablate a little bit lower, and then you just keep moving down the atrium.

The concept with this new inappropriate sinus tachycardia therapy that we're doing is a sinus node-sparing approach. So, we actually, in the past, had gone after the sinus atrial node thinking that that was the most effective way to treat these patients, and it can be very effective, and we have a very successful series with that. But if you ablate a lot of the SA node, then you lose the ability for the body to adapt and for that sinus atrial node to sell-regulate, if you will.

 The concept with this new therapy is to also use port access. But rather than ablating the SA node, what we're trying to do is ablate the autonomic input, if you will, or the extra stimuli that are affecting the SA node and causing it to go too fast. So, it's interesting to note that these signals actually come from the superior vena cava and even the inferior vena cava. And then, there's a huge autonomic ganglionic plexus, typically located near the pulmonary veins, which are right in proximity to this area. So, all three of those areas, and even up onto the crista terminalis are ablated, sparing the sinoatrial node. And what we do with this therapy is we do it together in the operating room with electroanatomic mapping, so that Kevin will do a baseline map, will identify where the SA node is.

And then, via the port access cameras, we'll put a little, if you will, a blue dye, mark the spot. And then, we know where it is, and then we come as close to it as we can without affecting the SA node. And we actually, if we get too close to it, sometimes we'll back away a little bit, but essentially try to denervate, if you will, or remove all the extra-anatomic stimuli of the SA node and spare the patient. And we actually did a very successful case last week.

Melanie Cole, MS: This is really exciting and absolutely fascinating how you two are working together. And as we talk a little bit about patient selection, Dr. Beaver, is your approach to managing this different in young, otherwise healthy individuals versus those with more complex medical histories because comorbid conditions, I imagine, would change the scope of what you're doing.

Thomas Beaver, MD, MPH: What we're learning with the younger patients is the tissues are a lot thicker and more durable. I think as we all know, as we get older, our tissues are a little easier to manipulate. So, the surgery is actually a little easier in the elderly patients rather than the young 20-year-old patients to your point about the other comorbidities. Of course, we have to manage, you know, just be cognizant of what other kidney disease or lung tissue. But typically, I don't know, Kevin, if you want to comment. But typically, these are younger patients that we're seeing, just by nature of the disease itself.

Kun “Kevin” Xiang, MD, PhD: Yes. Currently, we consider this disease as autonomic dysfunction. So, the diagnosis is exclusion of all secondary causes of tachycardia, means rule out structural heart disease or other chronic medical conditions. And those patients primarily only have this autonomic dysfunction to cause the sinus node to be at a high heart rate, high level.

The advantage of this new hybrid ablation approach is the sinus node is an epicardial structure means it is located at the surface, outside surface of the heart. So, use a mini invasive surgical approach, we can directly apply the treatment to the surface of the heart to decrease the nerve input to the sinus node. That's how we can reduce the heart rate. Another advantage is we can avoid those challenging complications such as phrenic nerve injury, also try to avoid patient to get a permanent pacemaker.

Melanie Cole, MS: Dr. Xiang, how are wearable devices, implantable monitors playing a role in the real time management? As we wrap up here, I'd like to give you each a chance for a final thought because this is so interesting for other providers. Speak about what's exciting in your field and how you're looking at these patients in a whole new way.

Kun “Kevin” Xiang, MD, PhD: All those patients have gone through multiple monitor studies for diagnosis purpose and for monitoring the treatment effect. Patients usually will have variable monitors to monitor for their average heart rate to correlate with their clinical symptoms. Sometimes we also implant those implantable cardiac monitors and monitor patient for long-term.

For patient who receive the ablations, we use the monitor to monitor their long-term responses to our therapy. We typically see a significant heart rate reduction post-ablation. So, the monitor gives us a way for diagnosis and for long-term monitoring of their symptom, correlate with the heart rate response. So, monitoring is an integral part of the whole diagnosis and the management.

Melanie Cole, MS: Dr. Beaver, I'd love to give you the last word here as we look forward to the future. And because this is relatively newer and very exciting, how do you see the management of IST evolving over the next decade? So, speak about that, your team and the multidisciplinary approach that's so important for these patients.

Thomas Beaver, MD, MPH: Yeah, I think I'd just like to highlight the fact that it's a team-based approach. It's a hybrid, it's part of a clinical trial. We're trying to get this technology approved as all these patients as part of the clinical trial being followed very closely. We're learning more every month about how to best manage these patients and, as we understand it better and we study the patients and the therapy itself, which we're excited about, I think, that the future looks bright for ISD patients.

Melanie Cole, MS: Thank you both so much for joining us today and sharing your incredible expertise on this topic. And to learn more about this and other healthcare topics at UF Health Shands Hospital, please visit innovation.ufhealth.org or to listen to more podcasts from our experts, please visit ufhealth.org/medmatters.

That concludes today's episode of UF Health MedEd Cast with UF Health Shands Hospital. I'm Melanie Cole. Thanks so much for tuning in today.