An Implantable Pulmonary Artery Pressure Monitoring Sensor to Improve Outcomes in Heart Failure Patients

Congestive heart failure (CHF) affects over 1,000,000 patients annually, with >3,000,000 hospitalizations with HF as a contributor (Figure 1). Management of congestive heart failure is difficult and one of the most common reasons for hospital admissions. The use of continuous pulmonary artery (PA) pressure measures can now be used to address the challenging management of the CHF patient.^1-5 We recently received the CardioMEMS Heart Failure System (St. Jude Medical) that uses a PA pressure transmitted from an permanently implanted mini-sensor placed in the cath lab via right heart catheter technique (Figure 2).  

Dr. Arnold Seto implanted our first three PA sensors and initiated this advance into our heart failure program. Continuous pulmonary artery pressure monitoring with this implantable sensor has been shown to improve management of CHF patients and reduce hospital readmissions, a critical measure of program success and quality of life for these patients. Recall that hospital readmissions within 30 days will be the focus of Medicare penalties moving forward.  

The application of the system is fairly straightforward. Once the sensor implanted, the pressure data is transmitted to the CardioMEMS system, and the information then facilitates the titration of medications to normalize PA pressure and maintain baseline thresholds. The system also provides email notifications of pressure deviations from baseline that may require intervention. As a new procedure in our lab, I thought it would be worthwhile to share our initial experience. 

CardioMEMS Candidates

Recently, the U.S. Food and Drug Administration approved the CardioMEMS Heart Failure System to measure PA pressure and heart rate in patients with New York Heart Association (NYHA) Class III CHF who have been hospitalized over the previous year. This approval was based in large part on the numerous supporting studies and specifically, the CHAMPION clinical trial, a multicenter, prospective, randomized, single-blind study. CHAMPION demonstrated that pressure-guided heart failure management is effective in maintaining stability of these high risk patients, resulting in fewer hospital readmissions for decompensation (see below).

Patients who are candidates are those with NYHA Class III symptoms, defined as having dyspnea-limiting activity with minimal effort. No ejection fraction criteria were used for selection. Thus patients with heart failure and preserved ejection fraction syndromes can be candidates. 

Patients with stage D heart failure or those in need of left ventricular assist devices, transplant, or continuous inotropic support were excluded from the CHAMPION study and not considered good candidates. Poor renal function (estimated GFR <25 ml/kg/1.73m²) was also an important exclusion criteria. Because the PA implant needs to endothelize, patients unable to tolerate clopidogrel and aspirin for six months after implant may not be suitable. Patients should be initially treated with maximally tolerated medications including appropriate dosing of ACE/ARB inhibitors, beta-blocker therapy, aldosterone antagonists, and other medications appropriate for management of congestive heart failure. Patients with cardiac resynchronization therapy (CRT) or implantable cardioverter-defibrillator (ICD) therapies can be selected on current clinical grounds and are not contraindication for PA pressure monitoring.

System Components

The CardioMEMS System consists of three parts: 

1. An implantable miniaturized sensor with no battery, positioned in the pulmonary artery via simple right heart catheterization using a 12 French (F) sheath (Figure 2). 
2. A sensor delivery transvenous catheter that is positioned in a distal pulmonary artery branch. 
3. The patient electronics system, a signal processing system comprised of an antenna (paddle, Figure 3) and processing unit (Figure 4). The paddle antenna is placed inside a special pillow. The patient lies on the paddle pillow and the pressure signals are sent when the paddle ‘pings’ the sensor. The implanted sensor signals are processed and transferred to the database for review and treatment decisions. 

Implantation Technique

Right heart catheterization from the femoral vein is performed by inserting a 12F sheath using standard technique. Use of ultrasound may be especially helpful to avoid the artery and find an easy vein to approach for safe puncture. Some patients can have the right heart cath via the internal jugular vein. The next step involves flotation of a standard Swan-Ganz or balloon wedge catheter to measure right atrial pressure, pulmonary capillary wedge pressure, and PA pressures. The PA branch to be used for sensor placement is confirmed by a small volume angiogram, performed with the balloon inflated (Figure 5). Then the balloon tip catheter is exchanged for the sensor delivery catheter. The left pulmonary artery has the most vertical and posteriorly directed branch segment.  This posterior location is most likely to reliably conduct left atrial pressures (West’s Zone 3 condition). Next, a long .018-0.025-inch exchange-length guidewire is inserted to facilitate placement of the sensor delivery catheter. The sensor delivery catheter positions the sensor in a vessel segment >7 mm in diameter (Figure 6). Once the position is accepted, a release knob on the end of the catheter is turned and the securing wire removed, permitting the release of the sensor (Figure 7). Because the loops and sensor are mostly radiolucent, only the faint outline of the sensor and four marker dots will be seen on fluoroscopy. The delivery catheter is then removed and the balloon catheter replaced to measure PA pressure just proximal to the device. The sensor paddle is placed behind the patient’s back, and calibration is performed with simultaneous PA catheter and PA sensor pressure measurements. 

Once released, retrieval of the device is not feasible with the delivery catheter. The large bore venous sheath can be removed immediately as no anticoagulation is required. Perclose closure device (Abbott Vascular) placement and subcutaneous temporary suture can be used to facilitate venous hemostasis, depending on operator preference. After implant, those patients on anticoagulation have their anticoagulation resumed, while those not on anticoagulation receive dual-antiplatelet therapy for one month, followed by aspirin alone.

Post Implantation Assessment

After device implantation, the patients are preferably observed overnight to provide education and teaching to the patient about their device. Patients are taught the appropriate method to perform interrogation of the sensor and troubleshoot the system when they are home. The procedure can also be performed with a same-day discharge provided appropriate education and training can be done. PA pressure information should be uploaded daily by the patient every time they lay on their bed at night. The patient should be told that she will not receive a phone call every time there is an upload; rather, they will only hear from the heart failure clinic staff should medication changes be needed. Workflow for the monitoring of pressure data in an established heart failure management program follows four simple steps:

1. Office receives notification of PA pressure.
2. Nurse calls patient.
3. Medications are adjusted.
4. PA pressures continue to be monitored for patient response.

Subsequently, the patient can be seen in the outpatient clinic as needed. The most common vasodilator used in the CHAMPION clinical trial was long-acting nitroglycerin with the afterload reducer, hydralazine. Vasodilator therapy is withheld should patients demonstrate hypotension or hypoperfusion, and require readmission to the hospital. Pressure ranges that appear to require action for either changing or up-titrating medications according to study recommendations are listed in Table 1.

The CHAMPION Study

The CHAMPION study¹ was a prospective, parallel, single-blinded, multicenter study that enrolled participants with NYHA Class III heart failure symptoms and a previous admission to hospital within the prior year. All patients received device implantation. Patients were then randomly assigned (1:1) to either the treatment group, in which daily uploaded pulmonary artery pressures were used to guide medical therapy, or to a control group where the data was not available to the treating investigators. Patients in the control group received all standard medical, device, and disease management strategies available. Patients then remained masked in their randomized study group until the last patient enrolled in the study completed at least 6 months of study follow-up (randomized access period) for an average of 18 months. 

During the randomized access period, patients in the treatment group were managed with PA pressure and patients in the control group had usual care only. At the conclusion of randomized access, investigators had access to pulmonary artery pressure for all patients (open access period) averaging 13 months of follow-up. The primary outcome was the rate of hospital admissions between the treatment group and control group in both the randomized access and open access periods. Analyses were by intention to treat. (ClinicalTrials.gov, number NCT00531661).

The Results of the CHAMPION Study 

Between Sept 6, 2007, and Oct 7, 2009, 550 patients were randomly assigned to either the treatment group (n=270) or to the control group (n=280). Three hundred forty-seven (347) patients (177 in the former treatment group and 170 in the former control group) completed the randomized access period. Over the randomized access period, heart failure admission rates were reduced in the treatment group by 33% (hazard ratio [HR] 0.67 [95% CI 0.55-0.80]; P<0.0001) and when pulmonary artery pressure information became available to guide therapy during open access (mean 13 months), heart failure admission rates in the former control group were reduced by 48% (HR 0.52 [95% CI 0.40-0.69]; P<0.0001). There was a shorter length of stay when patients were hospitalized.

Only 8 (1%) device-related or system related complications and seven (1%) procedure-related adverse events were reported. A better patient quality of life (Minnesota Living with Heart Failure Questionnaire scores) was also demonstrated. Of note, there were no pressure sensor failures and 98.6% freedom from device- or system-related complications.  

Real-world data based on Medicare claims were recently presented at the American College of Cardiology (ACC) and published. Amongst the 1141 patients receiving CardioMEMS implants between June 2014 and December 2015, there were 1020 CHF hospitalizations in the 6 months before the implant, and 381 CHF hospitalizations in the 6 months after implant (HR 0.55, 95% CI 0.49-0.61, P<0.001). This benefit, if true, would indicate that the device is even more effective than in the CHAMPION trial; however, the design of the observation study makes it impossible to separate the effects of the device from the increased intensity of monitoring after implant from the CHF clinic. In other words, was it the PA pressure measurements or the more frequent phone calls that led to fewer CHF admissions?

Caveats

In the CHAMPION trial, physicians treating patients in the treatment group received communication and advice from nurses trained and employed by the sponsor. This ‘extra’ coaching, not extended to the control group, was beyond the expectations of the FDA and led to initial FDA rejection. The device was ultimately approved after a longer follow-up and additional analyses performed, but this specter of unequal treatment makes the conclusions potentially biased. As a result, the CardioMEMS system has not yet been endorsed by the heart failure guidelines.

Although the device acquisition cost is high at $17,750-$25,000 each, several studies have suggested that the device can be cost effective, particularly when patients are carefully selected. Ideal patients would be those with recurrent hospitalizations and unstable disease despite optimal medical therapy and preserved renal function. Of note, the device is effective in both heart failure with either reduced ejection fraction or preserved ejection fraction, with a suggestion that it may be actually more effective in patients with preserved ejection fraction. 

Bottom Line

The PA pressure sensor technology now is simple and easily implemented in the cath lab. Caveats aside, this looks like a game changer for our patients with difficult-to-manage CHF. 

References

1. Abraham WT, Stevenson LW, Bourge RC, et al; CHAMPION Trial Study Group. Sustained efficacy of pulmonary artery pressure to guide adjustment of chronic heart failure therapy: complete follow-up results from the CHAMPION randomised trial. Lancet. 2016 Jan 30; 387(10017): 453-461.
2. Zile MR, Bennette TD, St. John Sutton M, et al. Transition from chronic compensated to acute decompensated heart failure, pathophysiologic insights obtained from continuous monitoring of the intracardiac pressures (CHAMPION study). Circulation. 2008; 118; 1433-1441. 
3. Martinson M, Bharmi R, Dalal N, Abraham WT, Adamson PB. Pulmonary artery pressure-guided heart failure management: US cost-effectiveness analyses using the results of the CHAMPION clinical trial. Eur J Heart Fail. 2017 May; 19(5): 652-660.
4. Desai AS, Bhimaraj A, Bharmi R, et al. Ambulatory hemodynamic monitoring reduces heart failure hospitalizations in “real-world” clinical practice. J Am Coll Cardiol. 2017 May 16; 69(19): 2357-2365.
5. Krumholz HM, Dhruva SS. Real-world data on heart failure readmission reduction: real or real uncertain? J Am Coll Cardiol. 2017 May 16; 69(19): 2366-2368.

¹Chief, Cardiology, Long Beach VA Medical Center, Long Beach, California

Disclosure: Dr. Kern is a consultant for Abiomed, Merit Medical, Abbott Vascular, Philips Volcano, ACIST Medical, Opsens Inc., and Heartflow Inc. Dr. Arnold Seto reports no conflicts of interest regarding the content herein.