New Center Studies Sudden Cardiac Death
DURHAM, N.C. -- When a young athlete seemingly at the peak of health drops dead while competing, the event draws national attention. Commentators wonder how such a catastrophic event could strike down someone with no apparent risk factors for heart disease.
At the newly created Duke Center for the Prevention of Sudden Cardiac Death, however, researchers understand that attention to such highly visible, infrequent episodes obscures the fact that sudden cardiac death is the most common cause of death in this country.
Thus, the new Center at Duke University Medical Center was created in part to raise the visibility of sudden cardiac death among the general public, policy makers, and the medical community. The Center's research aims to better understand who is most likely to suffer from a sudden cardiac event and to develop strategies for preventing its occurrence in at-risk patients.
The Center is led by Sana Al-Khatib, M.D., acting chief of cardiac electrophysiology at Duke and Gillian Sanders, Ph.D., medical decision analyst at the Duke Clinical Research Institute (DCRI).
"More than 40 Americans die every hour from sudden cardiac death," said Al-Khatib. "While the sudden death of an athlete grabs headlines, the reality is that many of those dying from sudden cardiac death are middle-aged and many would appear to be at low risk for a heart event. The truth is that sudden cardiac death is the most common and often the first manifestation of coronary artery disease."
"While the overall number of people dying from heart disease has declined over the past year, the proportion of the deaths attributable to sudden cardiac events has increased," Sanders said. "The reason for this increase is our inability to accurately identify those patients who will die suddenly and to better utilize therapies that we know can save lives."
In general terms, sudden cardiac death is the result of an abrupt and unexpected stoppage of heart function, usually the result of sustained ventricular arrhythmias. In these situations, the heart either beats more rapidly than usual in a condition state known as ventricular tachycardia, or it beats chaotically, as in ventricular fibrillation. A heart attack differs from sudden cardiac death in that a heart attack is the result of heart muscle that dies from the lack of nourishing blood flow
Since the underlying cause of most cases of sudden cardiac death can be traced to abnormalities in the heart's electrical system, one of the Center's focuses will be on implantable cardioverter defibrillators (ICD). ICDs are about the size of deck of cards and are surgically implanted under the skin of the chest, with wires attached to the heart. Whenever the device senses that the heart is in a life-threatening arrhythmia, it delivers an appropriate electric impulse to bring the heart back into proper rhythm.
Previous studies have demonstrated that ICDs are effective in preventing sudden cardiac death in patients who have already suffered from an arrhythmic event.
"However, when it comes to their effectiveness in preventing sudden cardiac death in a larger group of seemingly healthier patients, some of whom are at higher risk, we just don't know," Al-Khatib said. "Much more research needs to be conducted to pinpoint which subgroups of patients would benefit from ICD implantation."
In a recent study in the Journal of the American College of Cardiology, Al-Khatib showed that there was an inverse relationship between the experience of the cardiologist implanting an ICD and subsequent adverse outcomes. Inexperienced physicians had almost 50 percent higher rates of complications than did experienced physicians. A key function of the Center is to study the outcomes of patients receiving an ICD.
The ICD issue has staggering financial implications, Sanders said, since more than 500,000 patients could be eligible to receive the devices, which can cost as much as $30,000 per patient. Sanders led a study published Oct. 6, 2005, in the New England Journal of Medicine that showed the devices were only cost-effective for those patients who receive a significant mortality reduction. Another key function of the Center, the researchers said, is to study the cost-effectiveness of ICD use as well as other therapies used for the prevention of sudden cardiac death.
While agreeing to cover the cost of ICDs for now, the Centers for Medicare and Medicaid Services (CMS) has mandated participation of all hospitals in a National ICD Registry that will help answer many questions about which patients benefit the most from ICD therapy. .
In addition to conducting research into developing better methods for identifying at-risk patients, researchers at the Center plan to evaluate different interventions for preventing sudden cardiac death, to develop guidelines for the clinical application of different interventions, and to organize and coordinate clinical trials.
The Center will be housed within the DCRI and will be funded from numerous sources, including grants to individual researchers and on-going clinical trials. Center researchers will collaborate with scientists and policy experts across Duke University, as well as with experts at other universities, federal government agencies, industry, and patient support groups.