Dec. 8, 2011  

Proposed Implanted Medical Device for Monitoring Heart Failure Should Not Be Approved, Public Citizen Tells FDA

Device Has Serious Risks But No Known Benefits; Sole Controlled Clinical Study of Device Was Biased

WASHINGTON, D.C. – An experimental medical device proposed for monitoring patients with heart failure should not be approved because implantation of the device poses serious, life-threatening risks and there is a lack of evidence that the device offers significant benefits, Public Citizen said in testimony delivered today before a Food and Drug Administration (FDA) advisory committee.

The device, the CardioMEMS Champion HF Monitoring System (the CardioMEMS System) is intended for use in patients with moderately severe, symptomatic heart failure who have been hospitalized for this condition in the past year. Use of the device involves permanently implanting a small sensor in a branch of the pulmonary artery (a blood vessel carrying blood from the right side of the heart to the lungs). Implantation of the sensor requires insertion of a long catheter into a vein in the groin, advancing the tip of the catheter through the right side of the heart and into a branch of the pulmonary artery guided by X-ray imaging, and placing a small sensor in that branch of the pulmonary artery. Once in place, pressure within the pulmonary artery can be monitored using an antenna that is placed under the patient while lying flat in bed. Medical therapy for heart failure would then be adjusted based on the pulmonary artery blood pressure readings.

“Placement of the CardioMEMS System sensor involves undergoing an invasive procedure that presents risk of serious harm to patients, including risk of infection, bleeding (including bleeding into the airways of the lung), abnormal heart rhythms, blood clots and sometimes death,” Dr. Michael Carome, deputy director of Public Citizen’s Health Research Group, told the FDA’s Circulatory System Devices Panel of the Medical Devices Advisory Committee. “If this device were to be approved, it would be heavily promoted by the manufacturer of the device, and likely would be implanted in hundreds of thousands of patients. Given the known serious risks associated with implantation of the device, as well as likely unknown long-term risks, there must be evidence from well-designed clinical studies that the device has substantial clinical benefit for treating patients with heart failure. Such evidence for benefit does not exist.”

The manufacturer of the CardioMEMS System – CardioMEMS, Inc. – submitted data to the FDA from a single, large, randomized study of 550 patients with heart failure conducted at 64 medical centers across the U.S. All patients enrolled in the study underwent implantation with the device, and physicians for half of the patients were provided with the pulmonary artery pressure readings (the experimental group), whereas physicians for the other half were not (control group). The study showed less frequent hospitalization for heart failure in the experimental group subjects.

However, of particular concern to Public Citizen is that the way the study was designed and conducted created serious bias favoring the patients assigned to the experimental group, and as result, no valid conclusions can be drawn from the study about the benefits of the CardioMEMS System.The most egregious source of bias was identified during an inspection of the CardioMEMS System clinical study by the FDA’s Division of Bioresearch Monitoring. In its briefing documents for the Circulatory System Devices Panel, the FDA noted, “nurses working for the sponsor made medical recommendations for heart failure management for specific subjects during the course of the trial … limited to [experimental] group subjects only … the sponsor contacted investigational sites during the trial regarding recommendations for [experimental] group subjects with respect to starting, stopping and/or titrating specific heart failure medications, including doses, intervals and duration.”

“Such direct contacts between employees of the sponsor, who were highly motivated to affect the outcome of the study in a direction that favored use of the CardioMEMS System, and individual site investigators regarding management of only the experimental group subjects is highly unusual. Combined with the lack of investigator blinding (that is, investigators knew which group each patient was in), this created a high degree of bias in favor of the treatment group,” Carome said. “Such apparent bias prevents any valid conclusions from being drawn about the effectiveness of the CardioMEMS System. The FDA should not approve this device.” 

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