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Into The Digital Age: The Promise of Implantable Hemodynamic Monitoring in the Management of Pulmonary Arterial Hypertension


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Amresh Raina, MD
Allegheny General Hospital
Pittsburgh, PA, USA
araina@wpahs.org



In May 2014, the United States Food and Drug Administration (FDA) approved the first implantable hemodynamic monitor (IHM) for the treatment and monitoring of New York Heart Association (NYHA) functional class III heart failure (HF) [1]. The CARDIOMEMs device (St. Jude Medical, St. Paul, MN), is a wireless sensor placed in a distal branch of the pulmonary artery during right heart catheterization (RHC), and transmits measured pulmonary artery (PA) systolic, diastolic and mean pressures via an external console to a secure website, accessed by a patient's physician (Figure 1). This sensor also has the potential for measurement of cardiac output, but this algorithm remains to be validated.

Though this device was approved based on reduction of HF hospitalizations in patients with left heart failure [2], the hemodynamic information it provides could be easily applicable to the management of patients with pulmonary arterial hypertension (PAH).

Within two weeks of the FDA approval, one of our tech-savvy PAH patients posed exactly this question. He pulled out a picture of the CARDIOMEMs device printed from the internet during an office visit and asked whether he might be a candidate for this new technology, especially if he could access his PA pressures at home, and if the device could replace having future 'archaic' right heart catheterizations.

For better or worse, many PAH patients remain focused on PA pressures, as these are perhaps the easiest component of the hemodynamic assessment for a lay-person to understand and track, and, at least in the sentinel National Institutes of Health Registry, mean PA pressure was a main component associated with survival [3]. Though other hemodynamic variables, such as right atrial pressure and pulmonary vascular resistance (PVR), have subsequently been found to better predict outcomes in PAH patients [4,5], ongoing hemodynamic assessment may be useful in the management of PAH.

Indeed, there are several clinical scenarios where IHM data might be used to supplement traditional hemodynamic assessment with RHC. Perhaps the biggest advantage of IHM monitoring is that it provides ongoing and frequent assessment of a patient's hemodynamics in the outpatient setting. It can also give a more complete understanding of a patient's overall hemodynamics versus RHC which is performed intermittently at best, and under somewhat artificial conditions, typically supine and at rest. A recent small study of IHM monitoring in PAH patients showed that there was a more dramatic variation in PA pressures with daily activities versus with six minute walk testing, or even with cardiopulmonary exercise testing [6]. This becomes particularly relevant to the assessment of patients who have predominantly exercise-induced PAH symptoms and those who have borderline PAH (mean PA pressures 20-25 mm Hg) on resting RHC.

Another potential advantage with IHM monitoring in PAH might be in the prevention of hospitalization for right heart failure. In patients with left heart failure, a rise in PA pressures often occurs several days prior to the onset of new or worsening symptoms [7], allowing a window for medical intervention and prevention of hospitalization. The same logic could be applied to patients with PAH. Of course, PA pressures can rise due to an increase in PVR or an increase in cardiac output, but current IHM systems have the potential for estimating cardiac output to help discriminate between these possibilities. Moreover, in patients with PAH, wedge pressure is typically normal and assuming a normal wedge pressure, the IHM system could then provide an ongoing assessment of PVR.

Knowledge of PA pressure and PVR might also be helpful to rapidly gauge the efficacy of PAH specific therapy. For example, when starting oral agents, PAH clinicians initiate a therapy and then wait weeks to months before reassessing a patient's symptoms, functional status, right ventricular imaging, and potentially invasive hemodynamics. In two small studies with IHM monitoring in PAH patients, IHM data informed changes in medical therapy. Among two PAH patients transitioned from iloprost to bosentan, IHM data allowed clinicians to see the acute efficacy of bosentan over a week of therapy, allowing for successful discontinuation of iloprost [8]. In a multi-center study of 24 patients with PAH who had IHM implant prior to planned change in PAH therapy, the IHM data identified 13/15 patients who improved their six minute walk distance greater than 30 meters [9]. IHM data might also aid the titration of patients with intravenous prostanoid therapy, allowing the PH clinician to tailor a 'goal' dose individualized to the patient and their response to the particular prostanoid agent.

Finally, PAH patients may be able to enjoy a greater degree of autonomy and a reduction in the number of visits to the tertiary care center with the use of IHM monitoring. Many PAH patients live several hours away from tertiary PAH referral centers and participate in shared care with their local physicians. Through remote monitoring with an IHM, local physicians and those at referral centers may be able to facilitate shared care, reducing the need for long trips to a referral center and foc invasive procedures, such as RHC with its associated risk and discomfort.

So is the use of IHM systems in PAH ready for 'prime time'? Though the advent of this new technology is certainly exciting for the heart failure and PH community, patients and clinicians should be aware that the clinical experience to date with IHM systems in PAH is very small, and has been limited to small cases series and small multicenter studies, such that efficacy data remains lacking. Similarly, relatively little safety data exists with IHM devices in PAH patients, though the data that is available is positive. In the CHAMPION trial of the CardioMEMS IHM in 550 patients with left sided congestive heart failure, 48 (9.2%) patients had PH with a significant component of pulmonary vascular remodeling, a clinical phenotype similar to PAH. In this patient subset, there was only a single device/system related complication, which was actually associated with the implantation RHC [2]. The device/system related adverse event rate in this subgroup was not statistically different than the established rate of adverse events for a RHC in PH [10].

With the combination of so many possible benefits of IHM monitoring in PAH combined with the relative paucity of efficacy and safety data in this patient population, this may be an ideal time to consider a larger clinical trial of IHM monitoring in PAH patients and to consider use of IHM data as surrogate endpoint in future PAH therapeutic clinical trials. ■

Figure 1: CardioMEMS Heart Failure System Including Pressure Sensor, External Measurement Unit and Sample Pulmonary Artery Pressure Measurement Screen

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Disclosure Statement: Dr. Raina has received consulting and speaking fees from United Therapeutics Corporation.


References:

  1. FDA approves first implantable wireless device with remote monitoring to measure pulmonary artery pressure in certain heart failure patients.
    www.fda.gov/newsevents/newsroom/pressannouncements/ucm399024.htm. 2014.
  2. Abraham WT, Adamson PB, Bourge RC, et al. Wireless pulmonary artery haemodynamic monitoring in chronic heart failure: a randomised controlled trial. Lancet. 2011;377(9766):658-66.
  3. D'Alonzo GE, Barst RJ, Ayres SM, et al. Survival in patients with primary pulmonary hypertension. Results from a national prospective registry. Ann Intern Med. 1991;115(5):343-9.
  4. Benza RL, Miller DP, Gomberg-Maitland M, et al. Predicting survival in pulmonary arterial hypertension: insights from the Registry to Evaluate Early and Long-Term Pulmonary Arterial Hypertension Disease Management (REVEAL). Circulation. 2010;122(2):164-72.
  5. Humbert M, Sitbon O, Chaouat A, et al. Survival in patients with idiopathic, familial, and anorexigen-associated pulmonary arterial hypertension in the modern management era. Circulation. 2010;122(2):156-63.
  6. Kjellstrom B, Frantz RP, Benza RL, et al. Hemodynamic ranges during daily activities and exercise testing in patients with pulmonary arterial hypertension. J Card Fail. 2014;20(7):485-91.
  7. Zile MR, Bennett TD, St John Sutton M, et al. Transition from chronic compensated to acute decompensated heart failure: pathophysiological insights obtained from continuous monitoring of intracardiac pressures. Circulation. 2008;118(14):1433-41.
  8. Fruhwald FM, Kjellstrom B, Perthold W, et al. Hemodynamic observations in two pulmonary hypertensive patients changing treatment from inhaled iloprost to the oral endothelin-antagonist bosentan. J Heart Lung Transplant. 2005;24(5):631-4.
  9. Frantz RP, Benza RL, Kjellstrom B, et al. Continuous hemodynamic monitoring in patients with pulmonary arterial hypertension. J Heart Lung Transplant. 2008;27(7):780-8.
  10. Hoeper MM, Lee SH, Voswinckel R, et al. Complications of right heart catheterization procedures in patients with pulmonary hypertension in experienced centers. J Am Coll Cardiol. 2006;48(12):2546-52.



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