CD&D Contributing Editor
Heart failure is common, but often unrecognized and misdiagnosed. It is a progressive condition in which the heart's muscle becomes weakened after it is injured from a heart attack or high blood pressure and gradually loses its ability to pump enough blood to supply the body's needs. Its symptoms are often mistaken for signs of getting older. Heart disease has always been primarily a disease associated with aging.
Roughly 80% of heart failure patients are over 65. The incidence of heart failure is growing at 8% a year. Heart failure affects about 2% of patients between 40-59, and increases to about 10% for patients about 70.
Heart failure is a pervasive medical condition in the U.S. Roughly 5.3 million patients suffer heart failure and 660,000 new cases are diagnosed each year. The disorder is the primary reason for 12 million to 15 million office visits, 6.5 million hospital days and 55,000 deaths each year. About 20% of hospitalizations in the U.S. for patients above the age of 65 are due to heart failure. Medicare spends more on the diagnosis and treatment of heart failure than any other condition. The number of deaths from heart failure has increased steadily despite improvements in treatment.
The symptoms of heart failure may be subtle and often are mistaken for normal signs of aging (see Table 1). According to the Heart Failure Society of America (HFSA ; St. Paul, Minnesota), an estimated 5 million Americans currently suffer from congestive heart failure (CHF), and another 400,000 to 700,000 new cases are diagnosed annually. More than half of all CHF patients will die within five years of diagnosis and less than 25% of these patients are alive after 10 years.
CHF is the only major cardiovascular disorder on the rise, having experienced an increase in the number of deaths in the U.S. over the past 25 years. The number of deaths in the U.S. from CHF has more than doubled since 1979, averaging 250,000 annually.
CHF can be caused by a variety of underlying conditions, including hypertension, coronary artery disease, or a heart valve defect, all of which can initiate the complex cascade of events that lead to heart failure.
Echocardiography for diagnosing HF
Doctors often order a number of tests when exploring a possible diagnosis of heart failure. The current best practice is to perform an echocardiogram, or "echo," which determines a person's ejection fraction (EF), a standard measure of the heart's pumping effectiveness and a key indicator of heart health. It is the fraction of blood ejected by the left ventricle during the contraction or ejection phase of the cardiac cycle, or systole. People with a healthy heart have an EF of about 60%, while people with heart failure have an EF of 55% and below. An echocardiogram requires the use of expensive equipment and a highly skilled technician for its operation. It is performed in a hospital or clinic.
In a recent development, some of the major imaging companies – including GE Healthcare (Waukesha, Wisconsin), Philips Heaalthcare (Andover, Massachusetts), Siemens (Erlangen, Germany) and Dr ger Medical (Telford. Pennsylvania/Lubeck, Germany) — are beginning to target cardiologists' private practices, the offices of their referring physicians, and especially mobile cardiac response teams with lightweight and increasingly powerful ultrasound units.
Hand-held echocardiography is becoming the stethoscope in doctors' everyday work, Commercial products are Vivid i, a laptop-sized cardiovascular ultrasound system from GE Healthcare, Acuson P-10, a pocket-sized model from Siemens, and CX50 (CompactXtreme technology) from Philips that enables the early recognition of heart disease.
Thermodilution catheters for output monitoring
Cardiac output is used to measure how well the heart is performing its function of transporting blood to deliver oxygen, nutrients and chemicals to the cells of the body. Cardiac output is the volume of blood pumped by a ventricle in the heart, measured in liters per minutre. It is equal to stroke volume multiplied by heart rate. Stroke volume is the volume of blood pumped per beat and the heart rate is the number of beats per minute.
A Swan-Ganz thermodilution balloon catheter is used during cardiac surgery to monitor cardiac output. The catheter is inserted into the jugular vein and threaded to the heart. Cold saline is then injected into the heart. An electronic temperature sensor is used to measure blood flow based on temperature changes.
Companies that market thermodilution catheters include Arrow International (Reading, Pennsylvania), a subsidiary of Teleflex (Plymouth Meeting, Pennsylvania); Boston Scientific (Natick, Massachusetts); Bard Access Systems (Salt Lake City), a subsidiary of C.R. Bard (Murray Hill, New Jersey); Edwards Lifesciences (Irvine, California); and B.Braun Interventional (Bethlehem, Pennsylvania), a subsidiary of B. Braun Melsungen (Melsungen, Germany).
Impedance cardiography for monitoring
Impedance cardiography (ICG), also referred to as thoracic electrical bioimpedance, is a non-invasive method for monitoring cardiac output (measured in liters per minute), among other hemodynamic parameters. Echocardiography also is a non-invasive method for monitoring cardiac output but it is much more costly method, requires a highly trained personnel to perform, and is more time consuming.
ICG is performed using four dual disposable sensors that are placed on the neck and chest. They are used to transmit and detect electrical and impedance changes in the thorax, which are translated into blood flow data and used to calculate hemodynamic parameters. Around for several decades, ICG's initial acceptance was limited due to performance problems from signaling and noise processing irregularities. Dr. Robert Patterson, professor emeritus of biomedical engineering and physical medicine and rehabilitation and director of the Bakken Medical Instrumentation and Device Laboratory at the University of Minnesota (Minneapolis), had invented the use of ICG for measuring cardiac output.
In recent years, improvements in the accuracy of ICG technology have led to an increasing number of competitors that have entered this market with systems for use in hospitals and by physicians for managing cardiac patients with hypertension and heart failure. These companies are reviewed below
By far, the oldest player in this market is CardioDynamics (San Diego), which calls iself "the ICG company." It was founded as Bomed in 1983 and changed to its current name in 1993. Its BioZ Dx is an advanced diagnostic impedance cardiography (ICG) device for outpatient and hospital settings. It comes equipped with an EKG which uses 12 leads and was jointly developed with Philips.
The BioZ Monitor is a mobile system for outpatient and hospital use, and BioZ Module is an integrated module for use with patient monitors from GE Healthcare. BioZ ICG systems use Z Marc (Modulating AoRtic Compliance) algorithm to provide several hemodynamic parameters including cardiac output, stroke volume, systemic vascular resistance, and thoracic fluid content.
CardioDynamics markets its products worldwide to the outpatient market and let its OEM partners, including GE Healthcare and Mindray Medical International (Shenzhen, China), develop the hospital market for ICG.
CardioDynamics suffered a setback in 2005 when the Centers for Medicare & Medicaid Services (CMS) changed its reimbursement from covering all patients with hypertension to only covering patients with resistant hypertension. The policy also left coverage decision-making to each CMS contractor.
CardioDynamics is still recovering from this reimbursement change. It has not yet returned to profitability but has recrded seven consecutive quarters of year-over-year growth. Its annual sales are about $25 million, but the company estimates that the cumulative worldwide market potential for its BioZ product line at $2.1 billion.
In June 2007, CardioDynamics entered into a strategic alliance with Spacelabs (Issaquah, Washington) which enables joint marketing of Spacelabs' cardiac safety services and CardioDynamics' BioZ ICG and BioZ port application software. The agreement authorizes Spacelabs to utilize CardioDynamics' ICG products for use in centralized collection and processing of ICG data and to sell and rent CardioDynamics' ICG products for use in pharmaceutical and device clinical trials.
In January 2008, CardioDynamics reported a strategic alliance with Recorders and Medicare Systems (RMS), a large manufacturer of medical equipment in India. This agreement allows RMS to sell the BioZ ICG products in that country and also to integrate the BioZ ICG technology into RMS' patient monitoring products.
Also last year, CardioDynamics initiated the PREVENT-HF trial, a large, randomized and controlled trial to evaluate whether use of BioZ monitoring in chronic heart failure management will delay or prevent heart failure-related hospitalizations compared to standard care.
Cheetah Medical (Ramat Hachayal, Israel/Portland, Oregon) received FDA market clearance in January 2008 for its Reliant portable cardiac output monitor which provides non-invasive measurements of cardiac and hemodynamic functions. It uses the NICOM (NonInvasive Cardiac Output Monitor) system, which combines traditional impedance technology with Cheetah's patented Bioreactance technology.
Traditional bioimpedance analyzes changes in voltage of electrical currents traversing the patient's chest, while Bioreactance also analyzes frequency-related effects. NICOM's hybrid analysis helps deal with electrical noise interference, patient movement, respiration and electrode misplacement. The Reliant uses thoracic impedance cardiography with the measuring electrodes placed on the chest. Cheetah's Universal Unit is a laptop-mounted system. The NICOM ICU and CCU is a non-invasive cardiac output monitor based on hemodynamic reactance mapping and is intended for the measurement and display of cardiac output and ECG, both at rest and under medical tests.
Cardiotronic (San Diego), a subsidiary of Osypka Medical (Berlin, Germany), is primarily a developer and manufacturer of temporary cardiac pacemakers. Its Aesculon device has been available in Europe since 2005 and has an installed base of 30 to 40 units. The company received FDA 510(k) clearance for the Aesculon device in February 2008 and is in the process of developing its U.S. infrastructure.
It plans to use strategic alliances and its own sales force for distribution in the U.S. The Aesculon device employs a non-invasive method for continuous determination of cardiovascular parameters, including stroke volume/stroke index, heart rate, cardiac output/cardiac index, blood pressure, systemic vascular resistance, index of contractility, and thoracic fluid index. The stand-alone device requires four ECG surface adhesive sensors.
The Aesculon device measures changes in thoracic electrical conductivity (bioimpedance) as they relate to the orientation of red blood cells during diastole and systole. An electrical current is applied in the direction of the blood flow. The current passes more easily when red blood cells are aligned than when they are in random orientation. This method has been named electrical velocimetry (EV) and the application electrical cardiometry.
According to the company, EV differs from classical ICG in respect to the theoretical model applied and, thus, the interpretation of the measurements, which causes different signal processing and different algorithms for determining stroke volume. This method is distinguished from ICG because it is not limited to the monitoring of adults, but is also intended for monitoring children and neonates.
Noninvasive Medical Technologies (Las Vegas, Nevada) markets IQ2, a non-invasive hemodynamic monitor for assessing left ventricular cardiac function, including cardiac output, fluid volume, contractility, preload and after load. It provides hemodynamic evaluation in less than five minutes. The IQ2 does 3-D signal processing. Its sole contractor in the U.S. is the Department of Defense. It is marketed internationally for use in the ICU and in physician offices and is principally used to monitor hypertensive patients.
Hemo Sapien (Sedona, Arizona) markets the Hotman, a PC-based system for non-invasive hemodynamic assessment, monitoring, management and modeling of a patient's hemodynamics and oxygen transport dynamics, ranging from neonates to geriatrics. The product is used primarily as a guide for prescribing drugs. The product is available as modular and stand-alone systems.
The modular system is equipped with the external TEBCO (thoracic electrical bioimpedance cardiac output) module and notebook. It has its own power source and converts instantly any system (or a PC) with serial port into a continuous, non-invasive cardiac output and left ventricular performance monitor.
The TEB technology, also referred to as ICG, non-invasively measures cardiac index and nine other cardiodynamic parameters. Hemo Sapiens is an OEM supplier of TEB to other companies.
V samed (Eden Prairie, Minnesota) has developed the AcQtrac system for non-invasively accessing hemodynamic information and monitoring cardiovascular health. The AcQtrac system has an integrated cart that provides a portable platform. The system uses thoracic impedance cardiography (TIC) to present a cadiovasculogram waveform that illustrates the mechanical function of the cardiovascular system. The software is PC-based and information is provided in PDF format. A proprietary cardiac amplifier employs algorithms for providing a clear picture of cardiovascular health.
AcQtrac is marketed in Europe by a distributor in Greece and a few units are placed in U.S. hospitals, but it is not presently being actively marketed.
Conmed (Utica, New York) introduced at the UBS Life Sciences Conference in September its ECOM (endotracheal cardiac output monitor) for use in cardiac surgery. The company plans to soon begin marketing ECOM which was described as a "game-changing device."
The single-use endotracheal tube is use along with the device. ECOM's sensors are integrated into the endotracheal tube.