Issue



Effective monitoring for congestive heart failure


11/01/2007







By Nader Najafi, ISSYS

Congestive heart failure (CHF) is an epidemic, affecting more than five million U.S. patients and contributing to 300,000 deaths annually. The major problem confounding effective treatment is the lack of a safe, low-cost, easy method to regularly collect a patient’s cardiac pressure data. Direct measurement is currently limited to invasive and expensive procedures done in a lab and provides only snapshot data a few times per year at most.

Integrated Sensing Systems Inc. (ISSYS- www.mems-issys.com) is developing a monitoring system for safe, chronic, fast, detailed, real-time, continuous, cardiac pressure measurements to enable effective, tailored treatment over time. The system consists of a batteryless sensor that is implanted in a minimally invasive outpatient procedure; and a handheld reader that uses electromagnetic telemetry to power the sensor and enable it to transmit data to the reader. Data collection can be performed at a doctor’s office or at home by the patient and submitted over the telephone or Internet; the data provides the basis for custom treatment.


ISSYS’s implantable wireless, batteryless sensor.
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The most useful measurement for the CHF treatment is that of left atrial pressure-but making such measurements with an implanted sensor is two orders of magnitude more difficult than for other parts of the body (including right side of the heart and pulmonary arteries). This difficulty is due in part to the stringent requirement of non-thrombogenecity and in part to the difficulty to deliver and anchor implants. While other MEMS companies are targeting pulmonary application (no products are yet available), ISSYS is developing a total solution-based on feedback from cardiologists and cardiac surgeons-that is delivered via a catheter in an outpatient fashion and promises to monitor left atrial pressure with minute details.


The handheld reader powers the sensor to send data.
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At Wayne State University School of Medicine (Detroit, Mich.), ISSYS sensors were implanted in dogs both in the aorta and the right ventricle. The implant performs as well as the temporary Millar reference, often considered the gold standard of catheter-based pressure measurements. The ISSYS sensor’s response is clean and accurate compared to that of the lumen pressure sensor, which is usually used in cardiac catheterization procedures to assess CHF: The artifacts of the lumen sensor can lead to inaccurate systolic and diastolic pressure assessment. Biocompatibility studies of the ISSYS system show healthy tissue growth with no blood clot formation.


In two studies, the ISSYS sensor’s measurement fidelity proved equal to that of the “gold standard” Millar reference.
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Nader Najafi, PhD is president and CEO of Integrated Sensing Systems (ISSYS) Inc. He can be reached at (734) 547-9896 or at issys@mems-issys.com.