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Implantable hemodynamic monitors show promise in management of HF
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A major focus has been placed on intracardiac and pulmonary artery pressure-guided management to reduce HF hospitalizations and readmissions, according to a review published in the Journal of the American College of Cardiology. Novel approaches such as hemodynamic monitors have been in development, and studies such as CHAMPION have shown a significant reduction in HF hospitalizations in patients guided by pulmonary artery pressure compared with those in the control group.
Cardiology Today spoke with Leor Perl, MD, of the cardiology department at Rabin Medical Center in Petah Tikva, Israel, researcher at Stanford University School of Medicine and medical director for Vectorious Medical Technologies about implantable hemodynamic monitors, the benefits of using the devices and what the future holds for them.
Question: What are the pros and cons of current implantable hemodynamic monitors?
Answer: Currently, the utilization of any kind of invasive ambulatory hemodynamic monitors is very low. The only FDA-approved device is the CardioMEMS (Abbott). However, despite showing efficacy, the device is still not used in most medical centers for multiple reasons for now, but it’s up and coming.
Each device has different advantages and disadvantages. For the CardioMEMS, which is in the pulmonary artery, what you get is a reading that is a surrogate of what happens in the heart. It is good in estimating pressure, naturally, of the pulmonary artery, but that might be influenced by many other noncardiac medical conditions such as lung disease. The reading is not extremely accurate in predicting left atrial pressure, or left-sided filling pressures, within the heart. But it is the only one approved in the United States.
Since most patients do not have any kind of continuous invasive hemodynamic monitors, we are left to use our own clinical judgement, using signs and symptoms to assess for their status. That has been proven to be very inefficient and unsafe for the patients because their signs and the symptoms appear late and are deceiving, basically. Weight gain, for example, has been very low in terms of sensitivity and not very good at predicting who might be admitted and who might not. When we do become aware of relevant signs, it’s typically very late in the natural course of disease. When they start having symptoms, such as shortness of breath or edema, they usually are hours to a few days before being admitted. We’re missing out on an opportunity to intervene earlier on. Invasive hemodynamic monitors are able to predict their impending admission 2 to 3 weeks out.
Q: What does the next generation of technology add?
A: The V-LAP (Vectorious Medical Technologies) is an example of a next-generation device designed to answer the needs of patients with HF. It is without any compromise in terms of anatomy, robustness and design. It’s implanted in the proper place, the left atrium, which most experts would say — backed by scientific data — is the right location in terms of the ability to directly measure the left ventricular end-diastolic pressure and other crucial parameters of the heart, all extremely useful and provide very direct, robust information. The location also enables the detection of other medical conditions such as arrhythmias and valvular disease-like mitral regurgitation.
Another reason it is a next-generation device is that it is fully digital. The signal is processed within the device itself, which turns out to be an important issue because there is significant potential drift in measurement. Anything implanted within the biological system is ultimately and quite rapidly covered with different phases of cells and a layer of tissue. These entities will change the pressure measurement because there’s a small membrane for all these devices, and the membrane becomes covered with these types of material. The measurement that you get is not accurate anymore. You need to be able to compensate for drift. The V-LAP device has an active drift compensation mechanism, which understands how much drift is already taking place and how much error is potentially occurring. It will correct for that automatically. We already have a patented system to do that.
It has a digital signal that is transmitted to an external system remotely, and that external system is very comfortable. This is a belt- or a sash-like device that patients just put on whenever they want to measure their pressure, and they press the button. It is very user-friendly and easy to walk around with. You can run with it, whereas other solutions are more cumbersome and may require that the patient lie down. We can imagine patients giving up on daily measurements because these devices are so uncomfortable and so cumbersome.
Q: What is the advantage of direct measurement of left atrial pressure?
A: If you’re not in the left atrium and you’re trying to measure pressure within the heart, or trying to estimate what happens in the left atrium from what is right now typically the location of the pulmonary artery, what you might is no more than see trends in pressure. When the pressure increases greatly, the patients are congested and haven’t taken their medications for a few days. A trend will be shown that is probably good enough in some cases to predict an impending HF exacerbation, but the actual number is inaccurate.
Also for smaller changes, you might miss out on cases. The reason is that devices in the pulmonary artery are estimating what’s happening to the heart as they are looking through a network of arteries and veins that go through the lungs. If there’s no resistance in these vessels, then it is accurate, but over 50% of patients with HF, which is our patient population, have high pulmonary vascular resistance. In these cases, there’s a “screen,” meaning that the pressure that you’re reading in the pulmonary artery is looking through that some unknown factor. Is it 10 mm Hg, is it 5 mm Hg, is it 20 mm Hg? The reading is inaccurate. You’re not getting the right number, whereas if you’re directly in the heart measuring pressure within the left atrium with a good drift compensation mechanism so that you know that what you’re measuring is accurate, you’re getting better precision, better accuracy and, most importantly, better sensitivity in terms of assessing who might have an impending HF exacerbation.
Q: What other left atrial pressure and pulmonary artery pressure devices are in development?
A: I can’t speak for companies that are in stealth mode. Integrated Sensing Systems developed the Titan, a device that was supposed to also go into the left atrium. They published some data on how the procedure was simultaneously done with transaortic aortic valve replacement and LV assist device. During surgery, they simply implanted it, measured pressures and showed initial results. I’m not aware of any kind of progress in terms of drift.
The most famous one is HeartPOD (Abbott), a pacemaker-like device. It was another pioneer in the race to monitor pressures in the heart. It had a battery that was implanted transvenously and then electrodes going in through the septum entered the left atrium, in some cases requiring the use of a snare when using a transfemoral approach.
It showed some nice preliminary results in the hemostasis trial and then was prospectively assessed in the LAPTOP-HF trial. LAPTOP-HF was just recently halted because of complications, which we attribute to their design, one which required a major, unsafe procedure to implant the device. However, they did show a proof of concept, with the device being able to predict left atrial pressure and thus reduce exacerbations. The hemostasis trial was effective. But the initial design of the device was not safe enough.
We considered those factors when developing a fully leadless, wireless and miniature implant on the septum vs. something that is big and cumbersome and has electrodes and a battery.
Q: What are the implications for clinical practice?
A: That’s the exciting part. We are moving into a world where the health care system already understands the value of preventing events and treating them at home via monitoring patients. This happens in all sorts of disease states, from diabetes to MI. We want to make sure those patients are not even admitted, without getting to the point where they’re short of breath and in danger.
There’s an actual risk of about 12% for mortality for each time that the patient is admitted for HF. The costs associated with HF readmissions are staggering. Out of the billions of dollars that are being spent on HF, two-thirds are because of HF readmissions. If we’re able to save any of that and improve the quality of life for these patients, it would be a huge step for them because what they want more than anything else is to stay away from the hospital, but also to live longer and live happier.
The implications could be that we have the technology now to enable care of patients with HF outside of the hospital and we may impact their natural course of disease and have them stay happy and healthy at home with simply changing the dosages of medications or guiding them in a certain way, but not needing to have them admitted through the ED.
Q: Can you foresee any issues or complications regarding this new technology?
A: Any invasive procedure still has a minimal risk. Some patients are complex and have comorbidities. There will always be a risk. There’s enough experience, however, with similar devices at this stage. In 2017, we know pretty well how to perform procedures of this kind, which really is fairly simple. It’s a straightforward transseptal procedure where you cross, anchor, leave the device and get out. It’s a venous procedure, so the risks for bleeding are relatively low. We also have enough experience and understanding of what kind of medications we need to give these patients: essentially a protocol of antiplatelet therapy for a few months. We can estimate that the total risk of these procedures is fairly low. Remember, these are very sick patients, with 50% mortality after approximately 5 years. For them, the relative risk-benefit ratio should be favorable for devices of this sort.
Q: What further research is being done/would you like to see done in this area?
A: More research is being done in terms of the medication. All of these devices are for monitoring; the way that we treat and improve patients’ lives and prevent readmission is by fixing the dosage of the medication. It is tied to the medication regimen, the dosages, the compliance of these patients, and all of these things probably improve with better monitoring. That was shown in the CHAMPION study and other studies. They prove that when we have more data and more of an infrastructure to follow up on these patients, [there’s] more awareness by patients themselves.
There are a few classes of medications that are coming in. We’re not done with understanding even traditional medications such as furosemide. One recent study showed that by administering diuretics early on, you can reduce mortality, which was classically not thought to be part an effect of diuretics. There is information on all these classes of medications, what the benefits are and new classes coming in. That is an important part of how as an environment and as a system, we can treat these patients and how we may be able to improve their care.
There are a lot of data that will hopefully come in from different and new ways of assessing patient behavior and health such as all the electronic devices now. All of the smartphones are like medical devices. There are data to show what happens when behavior changes. With this device and other digital devices that collect a lot of data on these patients, we may be able to see trends of behavior. The V-LAP, for instance, will be able to report on a host of “secondary” disease states in addition to mean left atrial pressure such as arrhythmias and valvular disease.
We’ll get a lot of information and new type of research, new type of data on what actually is working for these patients, what are the hemodynamic parameters that are associated with readmissions, mortality and how does the medication impact the CV system.
Next, how do we improve compliance in patients? Now that we’re starting to become integrated into their lifestyle in an ambulatory setting, we hopefully will have some insight on how to improve compliance, how to have the patients and their families become engaged, and then improve the care of these patients not only in the hospital, but at home as well.
Q: What needs to be done before this technology becomes more common in clinical practice?
A: Abbott is making progress in terms of reimbursement for CardioMEMS. Given the sheer numbers of patients with HF and the magnitude of the problem, the unmet need is such that I believe that there will be multiple devices. We’re already seeing some therapeutic devices also, but in terms of HF hemodynamic monitoring only, there is a need for more competition, a variety of devices that fit different patients.
Some patients might not benefit from the device that is seeded in the pulmonary artery. They might need something that’s more robust, works for longer periods of time and is more accurate. These patients might benefit from another type of device.
At the end of the day, there will be adoption. We have to go through all the classical channels of regulatory reimbursement, but 10 years from now, I have no doubt that patients with HF will not wait and call in if they feel short of breath. We will be smarter and will be able to monitor them with these new technologies and prevent them from getting worse, helping them live a better lifestyle.
Q: How are these technological developments enhancing the management of patients with HF?
A: The CHAMPION trial has already shown a 37% reduction in HF admissions associated with what is only the first generation of HF ambulatory monitors. The next wave of invasive hemodynamic monitors will completely change the lifestyle and the path for these patients. We will be able to keep them out of the hospital and reduce costs. That’s the major point.
We are moving to the next generation of understanding patients, understanding their physiology and their personal life situation. It’s moving from the dark ages into a modern world of truly having data on patients and treating them accordingly. It’s the renaissance of HF patient management in an ambulatory setting. – by Darlene Dobkowski
Reference:
Abraham WT, Perl L. J Am Coll Cardiol. 2017;doi:10.1016/j.jacc.2017.05.052.
For more information:
Leor Perl, MD, can be reached at leor@vectoriousmedtech.com.
Disclosure: Perl reports receiving consultant fees from Vectorious Medical Technologies.