Implanted Heart Sensor Monitors Heart Failure Patients

The CardioMEMS HF System is a permanently implantable wireless system that provides pulmonary artery (PA) pressure measurements--including systolic, diastolic, and mean PA pressures--which can then be used by physicians to monitor the status of the patient and, if necessary, initiate changes in medical therapy, with the goal of reducing hospitalizations due to HF. The system consists of three parts: a permanently implanted sensor that utilizes radiofrequency (RF) energy for power; a transvenous catheter delivery system that deploys the sensor within a branch of the left or right distal pulmonary artery (PA); and the CardioMEMS hospital and patient electronics system.

The sensor itself is a resonant circuit consisting of a capacitor and an induction coil. The capacitance of the sensor is a function of the pressure in the sensor's environment, and the resonant frequency is a function of the capacitance. During an RF pulse, the sensor accumulates energy; when excitation stops, the energy is re-radiated by the sensor to the electronics unit. The pressure information is encoded in the frequency of the sensor signal, processed, and transferred to a secure database as an 18 second PA waveform or as a pressure trend data waveform. The CardioMEMS HF System is a product of St. Jude Medical (SJM; St. Paul, MN, USA).

“This new device will enable heart failure patients to live more comfortably, easing their worries as we closely monitor them for the earliest signs of fluid retention, a major cause of the symptoms of breathlessness and tiredness heart failure patients experience,” said Raymond Bietry, MD, assistant professor of cardiology at Mount Sinai Hospital (New York, NY, USA).

The mean PA pressure is typically 9–18 mmHg; pulmonary hypertension is defined as a mean pulmonary artery pressure of greater than 25 mmHg. This may occur as a result of heart problems such as HF, lung or airway diseases such as chronic obstructive pulmonary disease (COPD) or scleroderma, or thromboembolic disease.

Related Links:
St. Jude Medical
Mount Sinai Hospital