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EP LAB DIGEST. 2025;25(9):17-18.

Interview by Jodie Elrod

Bradley Knight, MD, and David Benditt, MD, discuss the moderated session on “Syncope: Novel Investigation Strategies and Treatment Approaches” at Heart Rhythm 2025.

Bradley Knight, MD: Hi, I am Dr Brad Knight at Northwestern. I'm the Editor-in-Chief of EP Lab Digest, and we're here at Heart Rhythm 2025 in San Diego. It has really been a fantastic meeting. I'm joined by my friend and colleague, Professor David Benditt from the University of Minnesota. For decades, he has been a leader in the evaluation and management of patients with recurrent syncope. For years, he has been an expert in the field. He just finished moderating a session entitled “Syncope: Novel Investigative Strategies and Treatment Approaches.” So, let’s start there. Tell me some highlights of that session that you just moderated. 

David Benditt, MD: It was a very interesting session. We had 4 speakers, all of whom are quite expert in their areas. One was from the University of Texas Southwestern Medical School. Dr James Daniels did a very fine job presenting the southwestern view of postural orthostatic tachycardia syndrome (POTS), which is a difficult problem for everybody. EP folks often end up seeing those people, even though perhaps they're not really accustomed to treating autonomic disturbances. Dr Daniels did a great job of presenting, because at UTSW, they've developed exercise protocols that are now widely used for that condition. In the second presentation, Dr John Lee from Saint Luke’s Mid America Heart Institute in Kansas City did a fine job discussing orthostatic hypotension. This is another problem that EP people often inherit that can be very difficult for them to deal with, because these folks often have neurologic problems. Differentiating the neurologic from the dehydration-type conditions can be a bit of a challenge in the clinic. But EP people tend to see these folks, so we must be alert to them. Dr Lee also discussed the various forms of orthostatic hypotension, which are very important to distinguish. We don't necessarily need to go into them here, but it helps doctors to prioritize the approach to therapy. The next talk was by Dr Satish Raj from Calgary discussing the so-called POST studies—there were 4 or 5 of them— looking at drug therapies for vasovagal syncope. The last was a nice presentation by Dr Sameer Jamal from Hackensack University also looking at POTS post-Covid syndrome, which is quite rampant. Again, EP people seem to inherit these patients, so we need to know more about them. 

Bradley Knight, MD: I recall in medical school a whole list of cardiac and non-cardiac causes of syncope. When we first see a patient with their first episode of syncope, it often leads to an investigation with an echo and things like that. But by the time we see these patients, they've usually had many of these tests already. Do you think that the causes of syncope and the prevalence of these causes differs now than it did 30 years ago? 

David Benditt, MD: I thought a lot about this particular issue, because especially with the Covid environment, you kind of see a little more syncope that we think might be inflammatory in nature. But overall, the causes are pretty much the same. Reflex syncope, which vasovagal syncope is the “big kid” in the house, is by far the most common still. From a physician's perspective, the history is really the key. So, it is like real estate, right? History, history, history, and then if you need a test, you can have a test. 

Bradley Knight, MD: I think we've been emphasizing that for decades too, and it still seems to be missed sometimes. 

David Benditt, MD: Syncope is a low priority in most training programs. So, the fellows don't get to really learn what you need to ask. It's not that it's intellectually very challenging, it's just that you have to know what to ask to get that information. Distinguishing these days, to speak to your specific question, POTS patients from orthostatic hypotension patients in a younger patient population is probably number 2 on the hit list for syncope doctors, because many patients get referred with POTS when they actually have orthostatic hypotension. They may fall into the overall group of postural intolerance, both of them, but they're different conditions and the orthostatic ones are much more common than the POTS. But one needs to ask the questions about the characteristic of the symptoms in detail. So much of the history that's taken is too superficial. 

Bradley Knight, MD: Yes, I think the term “unexplained syncope” is useful, because what you're interested in is getting to that point of, is it unexplained? If you take a careful history, a lot of time it's explained. What are the odds when they got up in the middle of the night to go to the bathroom that they had ventricular tachycardia when it could have been postural-related syncope?

David Benditt, MD: You're absolutely right. So, the key, and maybe to go back to the beginning before the beginning, is to make sure that it's a syncopal event when the patient went down. A lot of us see older people who will have falls due to accidents or they're unstable from orthopedic issues, and they fall and then are considered to be a syncope patient. It's pretty rare that we run into seizure disorders, but it happens occasionally. But I'd say that the key element in the history taking is not only to get a detailed history from the patient, but from eyewitnesses, such as spouses or people who were nearby. Get that information, because it fills out that portion of what you need to know before you select any tests. Too often, we test first and get the patient’s symptom details only afterward. 

Bradley Knight, MD: I think even a vagal episode of syncope as a bystander, witness, or family member can look quite traumatic. They may think that the patient practically died, when in reality, it could still have been a vagal episode. 

David Benditt, MD: Unfortunately, you are all too correct. And then what happens is people get very upset, and they don't recollect the detail. So, eyewitness reports cannot lead you to where you need to be, but it's worth at least asking. Also, bear in mind that vasovagal events are still very common in elderly people. If you look at the Newcastle data, syncope in young people less than 25 or 30, is probably 80% of syncope. But if you go to the 70-year-olds, it's still 50%. That is something we have to bear in mind, because the older folks do not have the same symptomatology. They don't tend to have the autonomic drive. So, you have to be aware when taking the patient’s history and be suspicious. 

Bradley Knight, MD: I wanted to get specifically to tilt table testing, because we do those adjacent to our EP lab, and it's one of the tests that our nurses really don't enjoy doing. There is a lot of pushback. I think we do fewer than we used to. We don't do tilt-guided drug therapy anymore and things like that, but there is still tilt table testing. What do you think is the role of tilt table testing? 

David Benditt, MD: I have a very sort of biased view of this. Tilt table testing, per se, was developed as a means to establish a diagnosis of reflex or vasovagal syncope. This was in the 1980s when EP people were just sort of getting involved in the field. We didn't really have any experience. Now, we have a lot more experience, so we need less tilt table testing for the purpose of diagnosis. But where it still comes in handy is when patients have seen multiple physicians and other providers without getting a satisfactory answer, and then they come to us; if we tell them that they just have vasovagal syncope, why are they going to believe us anymore than anyone else? So, tilt table testing can be useful to convince the patient that we've actually seen the episode and we know that they have the symptoms that they would expect to have at home, and that can be very conclusive in accepting the diagnosis. 

Bradley Knight, MD: And they now have a witness.

David Benditt, MD: They have a witness. So, tilt table testing is a bit more of a niche. So, other ways that tilt testing can be used is as part of an overall autonomic panel. We use it in conjunction with active standing tests, with Valsalva maneuver, and with respiratory sinus arrhythmia maneuvers, because we are looking to see if the basis for syncope was actually an autonomic dysfunction in a broader group of patients. That is another area where EP people are not trained to do that. So, we learn it day-to-day. But nevertheless, that's where tilt table testing has more value. Of course, it is in the guidelines for defining whether somebody has POTS or not. I'm a little skeptical that it's useful for that. 

Bradley Knight, MD: I think again, we've referred a lot of patients for tilt table testing who have never even had their orthostatics measured in clinic. It's just a poor man's assessment of their blood pressure and heart rate notwithstanding.  

David Benditt, MD: Orthostatic testing in the clinic is very important, but it has a major drawback, and that is many young people will present with what we term immediate orthostatic hypertension. They stand up and get a little woozy in the head. If you measure it on a beat-to-beat basis, their blood pressure falls by 40 to 50 millimeters of mercury and recovers very quickly, usually within 20 seconds total. You can never measure that in the clinic with a sphygmomanometer. So, there is some value to making that diagnosis because many young people present with orthostatic hypotension of that immediate form, and it's mistaken as POTS in the family practice clinic. So, you can make that diagnosis in the clinic.

Bradley Knight, MD: Good point. Since most of the discussion was related to autonomic disturbances, I'll follow up with another tilt table testing question. As you know, isoproterenol and nitroglycerin have kind of been provocative agencies in this country. We had a young patient who received sublingual nitroglycerin as part of provocative testing after a negative head-up tilt and had very prolonged asystole, to the point where the nurses started administering CPR. It was quite dramatic, and the patient was quite unhappy about the experience. I looked more into the literature about the value of these provocative tests. During the isoproterenol (Isuprel) shortage in the United States, a lot of us switched to nitroglycerin and it wasn't that strong. So, I think, to satisfy our team of nurses and this patient, we've actually stopped doing nitroglycerin. 

David Benditt, MD: Interesting. I've had a similar experience, but it's rare. I mean, you've probably done hundreds if not thousands of tilt studies and you have one bad example, right? I'm about in the same boat. 

Bradley Knight, MD: But if you find there's not much benefit to it, it's not just anecdotal. 

David Benditt, MD: Well, I might disagree a little. One has to be careful in interpreting the results, but the benefit is really in reproducing the patient's symptoms. So, you know the diagnosis, you know in your heart this is a vasovagal faint, but the patient doesn't know that, and they won't believe you unless you reproduce their symptoms. So, nitroglycerin can be a helpful project. Granted, you don't like experiences like that which are reported. But nevertheless, I'd say they're extremely rare. If you put that patient down back to a horizontal position, they recover. I don't know of a death associated with nitroglycerin infusion or sublingual nitroglycerin, which is what we use. 

Bradley Knight, MD: We're running out of time, but I'll close with asking you about syncope clinics. We don't really have a dedicated syncope clinic. People who run one make a strong case for one if you can kind of support that. Do you officially have one? 

David Benditt, MD: I am the syncope clinic, myself and our fellows. That's about it. But we do call it a syncope clinic, although we also deal with broader cardiovascular autonomic disturbances. That was supposed to be its name, but everybody just calls it the syncope clinic. So, the value of it seems to be best substantiated in Italy, where they have syncope clinics in many hospitals and have demonstrated reduction in cost and improvement in care. In the United States, it hasn't been taken up with that same enthusiasm. Mayo Clinic has had one, and they reported on it years ago, but very few other centers really advertise that. But I think more and more young EP people will be getting into autonomics because of cardioneuroablation and other things that the future may hold. I think that autonomic dysfunction in general will become more of an EP arena, and then the syncope clinics might sort of migrate more to EP. Whether that will be a happy outcome, I don't know, but it will be good for the patients.  

Bradley Knight, MD: I think we could probably talk for another hour. I have a lot of other thoughts, but I think we'll stop there. Thank you for summarizing that session. Thank you for your pearls, and it’s great to see you. 

David Benditt, MD: Yes, it’s great to see you. Thank you for the opportunity.

The transcripts have been edited for clarity and length.