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CardioMEMS: Experts in Intervention, HF Provide Their Take on the FDA Approval
In late May, the FDA approved the CardioMEMS HF System for the measurement of pulmonary artery pressure and heart rate in patients with NYHA class III HF who have been hospitalized for HF within the previous year, allowing health care professionals the ability to remotely monitor the condition of their patients. The system is the first permanently implantable wireless system intended to provide pulmonary artery pressure measurements, including systolic, diastolic and mean pulmonary artery pressures.
According to a press release, the CardioMEMS system (St. Jude Medical) is comprised of a battery-free implantable sensor/monitor that is implanted permanently in the pulmonary artery; a transvenous catheter delivery system that deploys the implantable sensor/monitor within the distal pulmonary artery; and the CardioMEMS Hospital and Patient Electronics System that acquires and processes signals from the implantable sensor/monitor and transfers pulmonary artery pressure measurements to a secure database.
With this approval comes the creation of a role for interventional cardiologists in the care of HF patients. To better understand the implications of this development, Cardiology Today’s Intervention interviewed experts in interventional cardiology — Jay Yadav, MD, consultant cardiologist, Piedmont Heart Institute, Atlanta, and founder and CEO of CardioMEMS — and HF management — Lynne W. Stevenson, MD, director of the cardiomyopathy and heart failure program, Brigham and Women’s Hospital, Boston, and professor at Harvard Medical School — to get their take on this first-of-a-kind technology and what it will mean for practice.
CardioMEMS: The Formative Years
Jay Yadav, MD: The impetus for the CardioMEMS device was that I noticed we had a lot of HF patients who were admitted to the ICU with decompensated HF and pulmonary edema. My thought was that if we had gotten the hemodynamic information we get from a right heart catheterization earlier, when patients are still at home, we could have adjusted their medications and prevented the decompensation so they would not have ended up in the hospital.
Jay Yadav
This turned out to be a really hard problem to solve. I could have taken the approach of using the traditional pacing technology of batteries and leads, but I had dealt with the complications of leads, in the subclavian vein and superior vena cava, and didn’t want to have a lead-based system. I also wanted to avoid the battery so as to create a truly permanent implant, utilizing wireless power, which nobody had done before. Compounding the challenge, we needed a stable sensor, which was problematic because sensors are traditionally unstable, as their baseline drifts over time, so if you calibrate them today by tomorrow the information is no longer accurate. With CardioMEMS, we created a sensor that, instead of drifting millimeters per day, drifts 0.1 mm in a year, making it the world’s most stable sensor. As a result, patients don’t require an additional heart catheterization for recalibration.
After the development, we needed clinical evidence to support the hypothesis that having the information would prevent hospitalizations. What followed was the large, randomized CHAMPION trial that took several years to complete. What we found, resoundingly, was that having this information did allow doctors to manage patients better and reduce hospitalizations.
Lynne W. Stevenson, MD: When I first began to get involved with HF back in the 1980s, most patients didn’t live more than a year after being referred for transplant, so there wasn’t a long period of severe symptoms. But with ACE inhibitors and beta-blockers and then implantable cardioverter defibrillators (ICDs) and more recently cardiac resynchronization therapy devices, patients began to live a long time with HF, which was and continues to be very gratifying. But the major limitation of recurrent fluid retention remained. We realized that we were not as effective as we needed to be to keep patients stable, as indicated by the high rate of rehospitalizations. Patients would be admitted to the hospital, we would decongest them and get rid of the fluid and they would feel good and go home; however, often within 30 days, they would be back again. So we had a high rate of rehospitalization due mainly to the symptoms of congestion: shortness of breath with exercise, shortness of breath lying down, poor appetite with abdominal distention, and the discomfort of edema. Early on in the development of the monitoring technology, a group of physicians, including Robert C. Bourge, MD, William T. Abraham, MD, Philip B. Adamson, MD, and myself, were asked what we needed to know and we said the cardiac filling pressures when patients are home. That really led to our understanding of the physiology of recurrent congestion. We had beautiful data transmitted from a 24-hour in-home monitoring system (Chronicle, Medtronic). Before this, we had thought decompensation was a sudden event, but what we found was that the pressures start to go up, on average, 2 to 3 weeks before clinical evidence of deterioration. With this new information, we realized we needed to find a better way to see the increase coming so we could avert it. However, after clinical research in the COMPASS-HF trial, we realized the Chronicle device was not the right technology to make monitoring generalizable.
Afterward, the same group realized our mistake in treating the pressures only when they started to go up instead of getting the pressures down to a safer baseline. What we learned from the COMPASS-HF trial was that patients who live at a more normal plateau of pressures are much less likely to have a hospitalization when their pressures go up a little. Then when we came to testing the CardioMEMS device, we had a much stronger strategy: We would not just treat the pressures when they went up; we aimed vigorously to lower the pressures patients were living with every day down to closer to normal levels, giving them much more of a margin. That is really what we believe led to the dramatic success of the CHAMPION trial. One of the most dramatic observations was among patients with HF with preserved ejection fraction (HFpEF). These patients are often very brittle and have a narrow window of fluid balance that works well for them, between too wet and too dry. We were able to keep patients with HFpEF out of the hospital who had been hospitalized almost every month, and some we were able to keep out of the hospital for 2 years once we had this information.
Procedural Aspects
Yadav: Most interventionalists have a lot of experience with physiologic information obtained during cardiac catheterizations and that helped me conceive of the device in terms of the utility of the information gathered during a catheterization. I also knew the procedure needed to be not only safe, but also capable of being performed by physicians who are not interventionalists, which is important because HF is a major problem that is treated by all cardiologists. What resulted is a straightforward and safe procedure that anyone who performs a right heart catheterization can do. In fact, in our trial, most of the implanters were HF cardiologists, followed by interventionalists and electrophysiologists.
Stevenson: The procedure is performed very much like inserting a pulmonary catheter. You insert the device into a small branch in the pulmonary artery where it lodges. It is not connected to anything, which is different from all the other technologies that have been tried. Its power source is external: You put a power source on top of the device to supply the energy to read it. This is another real advantage because you are not tied up with leads that connect to a box. It’s freestanding in the small branch of the pulmonary artery.
Since our institution has people who work in the cath lab all day, we had them insert the device, which is how I think it will be done at many centers. However, on the scale of procedures, CardioMEMS is a very simple one to perform.
Potential for Paradigm Change
Yadav: Right now, HF management is very inefficient. Physicians are left relying on symptoms and many tests that aren’t very good. Through two large randomized telemonitoring trials, we have learned that talking to patients on the phone regarding their symptoms is not effective. The CardioMEMS device dramatically improves the efficiency and outcomes of managing HF patients, and will fit well into the interventionalist’s practice. Currently, many interventionalists take care of HF patients, as many of their MI patients develop HF. Having this device helps the interventionalist because it is physiologic, efficient, a device-based therapy and provides the kind of information that interventionalists are very comfortable looking at and dealing with.
The recently FDA-approved CardioMEMS HF System, which is placed in the pulmonary artery
via a transvenous catheter delivery system, is smaller than the size of a dime.
Photo courtesy of CardioMEMS
Stevenson: This is going to create the chance for many cardiologists to finally understand what’s going on with their patients’ HF at home. At the moment, there are only about 480 HF specialists in the country and there are about 6 million people with HF, so clearly the new monitoring system will not be used solely by HF cardiologists. One of the most exciting opportunities is for the electrophysiology clinics to get involved because the transmission and central website should be relatively similar to what they currently use to manage ICDs and CRT devices.
Long-Term Impact
Yadav: My opinion is that the CardioMEMS device will reduce HF admissions and readmissions quite a bit in clinical practice. The clinical trial evidence was dramatic. We reduced admissions by 37%, and reducing admissions will effectively reduce readmissions. Importantly, we already have Medicare reimbursement, as we received it before FDA approval. Medicare is really concerned about the cost of HF and was pleased that we were able to significantly reduce HF admissions. There are monitoring codes already built in, so both the implant and follow-up are paid for. As a result, the adoption of CardioMEMS should be widespread and really good for patients and all cardiologists, while at the same time playing to an interventionalist’s strengths.
Stevenson: I would anticipate the CardioMEMS technology will cause a dramatic change in workflow for HF management programs because it will become part of what we do every day. The workflow is going to include much more objective information about our patients, including data on those who are undergoing changes in their therapy at home, as well as alerts when patients are gradually slipping out of stability.
Accordingly, CardioMEMS should decrease the number of rehospitalizations that are related to recurrent fluid retention, which is most of the current HF rehospitalizations. This will also give both the patients and the staff who take care of them more confidence in dealing with issues over the phone. If a patient calls and says “I just don’t feel right today,” we can now distinguish better whether this is related to HF.
In the long run, my hope is that we are going to change the natural history of HF. If we look at what causes HF to progress and become end stage, it is often progression of left HF to right HF, which relates to elevated left-sided, right-sided and pulmonary pressures, and the development of tricuspid regurgitation. I am hoping that being able to keep the left ventricle decongested will interrupt this gradual progression of HF from the left backward into the right; and if we can maintain the right ventricular function then we have basically changed the picture of HF. Even when the LV function is chronically reduced, it is often when the right ventricle fails that patients develop malnutrition and cachexia and renal function begins to deteriorate. I’m hopeful that if we can keep the left-sided filling pressures in the optimal range, we will be able to prolong the period of good quality of life and compensation with HF.