Healthcare Industry News: Microvolt T-Wave Alternans
News Release - November 15, 2006
Results of Clinical Trial Demonstrate That a New, Non-invasive Test is Comparable to Invasive Tests in Identifying Patients Who Could Benefit from ICDs
Trial Results Presented Today at American Heart Association 2006 Scientific SessionsCHICAGO--(HSMN NewsFeed)--New clinical trial results from the Alternans Before Cardioverter Defibrillator (ABCD) trial were presented today at the American Heart Association's 2006 Scientific Sessions conference in Chicago. The study found that a non-invasive test that uses computer technology to predict a patient's risk for sudden cardiac death has proven itself comparable to an invasive and more expensive procedure commonly used by cardiac electrophysiologists to determine a patient's eligibility for an implanted defibrillator.
Primary Investigators Otto Costantini, M.D., and David S. Rosenbaum, M.D., from the MetroHealth Medical Center campus of Case Western Reserve University in Cleveland, Ohio, presented the results. The study, sponsored by St. Jude Medical, Inc. (NYSE:STJ ), compared the predictive value of Cambridge Heart, Inc.'s (OTCBB:CAMH ) non-invasive Microvolt T-Wave Alternans (MTWA) Test(TM) with traditional, invasive electrophysiology (EP) tests in patients with a history of ischemic heart disease at high risk for sudden cardiac death (SCD).
This first-of-its-kind study investigated the use of MTWA, in which electrocardiogram sensors are placed on the chest, to eliminate or reduce the need for more costly and complicated invasive tests, where catheter electrodes are placed into the patient's heart and electrical impulses are delivered to deliberately induce an abnormal heart rhythm.
It is anticipated this new tool will be used by referring physicians to better identify which patients have life-threatening arrhythmias and need therapy provided by implantable cardioverter defibrillators (ICDs). Current estimates show that only one in eight patients who needs such a device actually gets one implanted. SCD from ventricular arrhythmias accounts for nearly 50 percent of all cardiovascular deaths worldwide and, although treatable with an ICD, it's difficult to predict which patients are most at risk.
Rosenbaum, the study's senior author and director of the MetroHealth Heart and Vascular Center, said, "The current test used to identify patients at risk for SCD who might benefit from ICD therapy has significant limitations. Consequently, most patients who are likely to benefit from ICD therapy are not receiving it, and conversely, most patients who receive ICDs never experience an arrhythmia."
"Many SCD events occur without warning and 95 percent of people do not survive the first episode. The ABCD trial will give referring physicians a non-invasive means of categorizing a patient's risk," said Eric S. Fain, M.D., executive vice president of Development and Clinical/Regulatory Affairs for St. Jude Medical's Cardiac Rhythm Management Division. "We are optimistic about the possibility of providing an easier, more cost-effective, early warning system for the more than 335,000 Americans stricken by SCD each year."
"The positive and negative predictive values of a MTWA-directed strategy and that of an EP test alone were essentially identical," said Costantini. "This is most important, as the clinically relevant question today is not who should receive an ICD, but who is unlikely to benefit from ICD therapy. The use of a non-invasive approach to help us answer this question represents a significant step forward."
About EP and MTWA Testing
Typically, patients referred for one of the tests have already demonstrated poor cardiac performance on an echocardiogram. The American Heart Association estimates that 5 million Americans suffer from heart failure, meaning their heart muscle is not pumping effectively. Many of these patients may be candidates for an implanted defibrillator.
"The EPS is an invasive procedure in which a catheter is threaded through a patient's veins into the heart where it delivers electrical stimulation to set off an arrhythmia," said Rosenbaum. "The EP testing carries a small risk and requires a high degree of expertise, limiting its ability to be used as a widespread screening tool."
The non-invasive MTWA test is similar to a stress test, where the patient walks on a treadmill while electrical sensors attached to the skin surface record changes in the heart's electrical activity. However, unlike a stress test, the MTWA uses a computer program to analyze subtle differences in the electrocardiogram's T-wave from one beat to the next. Physicians first noticed the association between a difference in T-wave patterns and the risk of SCD more than a century ago, but advanced technology has made it possible to analyze them to predict SCD.
"The MTWA test provides a fast and inexpensive method for a physician to identify high risk patients in need of ICD therapy right in their own office," said Jeff Langan, president and CEO of Cambridge Heart. "The results of this clinical trial show that the Spectral Analytic MTWA test is comparable to the 'gold standard' invasive EPS, and therefore should provide physicians with additional confidence in their diagnosis when utilizing our technology."
Sudden Cardiac Death
SCD, also called sudden cardiac arrest, is unexpected death resulting from an abrupt loss of heart function caused by a rapid irregular heart rhythm (arrhythmia) or cardiac arrest. Many people have no symptoms until the SCD occurs, and the majority of patients suffering SCD do not survive the first episode. Cardiac arrest is reversible in most victims if it's treated within a few minutes with an electric shock to the heart to restore a normal heartbeat. According to the American Heart Association, about 335,000 people a year die of coronary heart disease without being hospitalized or admitted to an emergency room; most of these are sudden deaths caused by cardiac arrest.
An ICD detects arrhythmias, both bradyarrhythmia (slow heart rates) and tachyarrhythmia (fast heart rates), and delivers electrical therapy-pacing pulses or defibrillation therapy as necessary to treat these rhythm disorders and restore normal rate and rhythm to the heart. When not needed, the ICD merely monitors the heart without delivering any electrical energy. ICD therapy is often prescribed for patients who have experienced at least one episode of ventricular tachyarrhythmia, ventricular fibrillation, previous cardiac arrest or drug therapy that was ineffective in controlling the tachyarrhythmia or that caused severe side effects.
"Patients with heart damage, like those in the study, are at increased risk of sudden death, a condition in which the heart beats rapidly or chaotically and then stops," said presenter Costantini, who is assistant professor of medicine at the MetroHealth campus of Case. "The condition causes death within seconds unless the heart is given an electrical shock, such as that delivered by an ICD, allowing a normal rhythm to resume."
About the ABCD Trial
The ABCD trial, initiated in May 2001, followed 566 patients, 18 years of age and older, at 43 medical centers in the United States, Germany and Israel, for a median of 1.9 years. Trial enrollment was completed in 2005 and follow-up ended in June 2006. All participants underwent MTWA and EP tests with blinded and central adjudication of all test results; St. Jude Medical ICDs were implanted if either test was positive and at the physician's discretion if both tests were negative.
All patients had previous heart damage from coronary artery disease but, importantly, none of the patients had previously experienced a cardiac arrhythmia. The patients had both EP and MTWA testing and received an ICD if either or both tests were positive, making this the first trial in which patients received active therapy based only on a positive MTWA test. "MTWA directed" strategy was defined as positive if either the MTWA test was positive, or if the MTWA test was indeterminate and the EPS was positive.
EPS and MTWA directed strategies had comparable one year positive (11 percent and 9 percent, respectively) and negative (96 percent and 95 percent, respectively) predictive values. Event rates were higher at one year in patients with ICD therapy guided by both MTWA directed (HR=2.1, p=.03) and EPS alone (HR=2.4, p=.007) strategies. The event rates for patients with both a negative MTWA test and EPS were 2 percent.
Over two years, physicians monitored patients every six months to see if their ICDs had been activated. Researchers found that the overall rate of arrhythmic events was 7 percent after one year and 13 percent over two years. The study showed that a strategy for screening patients for SCD risk which includes MTWA could greatly improve the process of selecting patients who can benefit from ICD therapy.
"There is rationale for incorporating more than one risk stratification test, which is understandable, given that changes produced by heart disease are very complex," said Rosenbaum. "It also makes sense because the tests measure different things: EPS measures how electrical waves spread across the heart as it beats and the MTWA measures how the heart cells recover from those electrical activities. We need to adopt the mindset for SCD screening that we currently have for breast cancer screening: Like the mammogram, SCD screening should be applied to appropriately selected patients at regular intervals. Ultimately the patient and physician need to decide what level of risk is acceptable."
Another important finding was the unexpected time dependency of risk markers for SCD. "We found that the EP study was not predictive until nine months or more and then remained predictive for two years, while the MTWA test was predictive as early as six months but was no longer predictive of outcomes by 12 months," Rosenbaum said. "The findings suggest that the abnormalities in heart disease that increase the risk of arrhythmia are highly dynamic and change over time, which suggests periodic screening may be beneficial."
About Microvolt T-Wave Alternans
Cambridge Heart's Microvolt Alternans Test measures very small beat-to-beat fluctuations of the T-wave amplitude on an electrocardiogram (ECG). These tiny heartbeat variations - measured at one millionth of a volt - are detected using proprietary Alternans Sensors while the heart rate is elevated by exercise, use of pharmacological agents or pacing. Extensive clinical research has shown that patients who show symptoms of life-threatening arrhythmias and test positive for Microvolt T-Wave Alternans are at significant risk for subsequent sudden cardiac events, including SCD.
About MetroHealth
MetroHealth offers a full range of healthcare services at 14 sites throughout Greater Cleveland. With its commitment to research, medical education and community service, MetroHealth is able to provide the best care to the most people. MetroHealth is a major affiliated teaching hospital of Case Western Reserve University. In addition to the Heart & Vascular Center (www.MetroHealthHeart.org), services include a Level I trauma center, burn center, comprehensive cancer care, high-risk obstetrics care, neonatal intensive care, women's health, pediatrics, medical and surgical specialties, family health, internal medicine, mental health, rehabilitation, long-term care and community health.
About Cambridge Heart, Inc.
Cambridge Heart is engaged in the development and commercialization of products for the non-invasive diagnosis of cardiac disease, in particular addressing such key problems in cardiac diagnosis as the identification of those at risk of sudden cardiac arrest. The Company's products incorporate its proprietary technology, Microvolt T-Wave Alternans, coupled with its patented Spectral Analytic Method, which have been cleared by the U.S. Food and Drug Administration to non-invasively measure microvolt levels of T-wave alternans. The Spectral Analytic Method MTWA test is the only MTWA reimbursed by Medicare and major insurers in the United States, and is included in guidelines for cardiac care in the United States and Europe. The Company, founded in 1990, is based in Bedford, Mass., and is traded on the OTCBB under the symbol CAMH. Cambridge Heart can be found on the World Wide Web at www.cambridgeheart.com.
About St. Jude Medical
St. Jude Medical is dedicated to making life better for cardiac, neurological and chronic pain patients worldwide through excellence in medical device technology and services. The Company has five major focus areas that include: cardiac rhythm management, atrial fibrillation, cardiac surgery, cardiology and neuromodulation. Headquartered in St. Paul, Minn., St. Jude Medical employs approximately 11,000 people worldwide. For more information, please visit www.sjm.com.
Forward-Looking Statements
This news release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 that involve risks and uncertainties. Such forward-looking statements include the expectations, plans and prospects for the Company, including potential clinical successes, regulatory approvals, anticipated future product launches, revenues, margins, earnings, and market shares. The statements made by the Company are based upon management's current expectations and are subject to certain risks and uncertainties that could cause actual results to differ materially from those described in the forward-looking statements. These risks and uncertainties include market conditions and other factors beyond the Company's control and the risk factors and other cautionary statements described in the Company's filings with the SEC, including those described in the Company's Annual Report on Form 10-K filed on March 16, 2006 (see Item 1A on pages 15-21) and in the Company's Quarterly Reports on Form 10-Q filed on August 7, 2006 (see Item 1A on page 32) and November 7, 2006 (see pages 31-32). The Company does not intend to update these statements and undertakes no duty to any person to provide any such update under any circumstance.
Source: St. Jude Medical
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