Sudden Cardiac Death Subject of Sweeping UCSF Study

June 15, 2011
News Office: Jeffrey Norris (415) 502-6397

Researchers at the University of California, San Francisco's Cardiac Electrophysiology Service are seeking to discover for the first time the true causes of sudden cardiac death (SCD), and why it is more prevalent in certain populations.

Working with the Office of the Chief Medical Examiner for the City and County of San Francisco, researchers will fully investigate every death in San Francisco attributed to a sudden cardiac event over a three-year period. They hope to identify the biological risk factors for the disease and to improve medical therapy.

The rich character and cultural composition of San Francisco make it an ideal microcosm for such population studies. According to the U.S. Census Bureau, in about 30 years the level of ethnic diversity for the nation as a whole will reach San Francisco's current level of ethnic diversity. The researchers hope that the study will result in valid predictors for the prevalence and causes of sudden death within the entire U.S. population.

Recognizing the need for timely research in sudden death, the National Institutes of Health has awarded $1.9 million to UCSF to enable Dr. Zian H. Tseng, assistant professor of medicine in UCSF's Cardiac Electrophysiology Service, to mount a comprehensive, community-based project with the medical examiner's office, to which the deaths are reported.

"More than anything, we want to prevent SCDs by understanding who is at highest risk for the disease and which medical interventions, such as defibrillators, are likely to be most effective," Tseng said. "To do that, we need to know the prevalence in various populations of risk factors such as inherited arrhythmias, and whether an individual actually died of SCD rather than an aneurysm, for example. A great way to collect that data is to utilize public information already being collected by the medical examiner's office."

According to Dr. Amy Hart, San Francisco's chief medical examiner, "This research will inform not only a large public health problem, but could also advise future policy."

Dr. Ellen Moffatt, assistant medical examiner and a collaborator on the study, added, "We are excited to partner with Dr. Tseng on this important project. Sudden cardiac deaths make up a large burden of overall mortality."

Sudden cardiac death affects an estimated 295,000 people per year and incidence varies among ethnic populations. African-Americans, for example, suffer a rate nearly three times higher than Caucasians. SCD is defined by the American Heart Association as death resulting from an abrupt loss of heart function, or cardiac arrest, in which the victim may or may not have been previously diagnosed with heart disease. The time and mode of death are unexpected and occur within minutes after symptoms appear.

There are many reasons to conduct the study, according to Tseng. Little is known about the underlying causes of sudden death or what accounts for the observed racial disparity. The disease has not been widely researched; what knowledge does exist is nearly 30 years old and has been derived mostly from studies of homogeneous Caucasian populations, which probably included some subjects who actually died due to other causes.

During the second phase of the study, the research team will build a database of the cases, including clinical data from the deceased subjects' past medical records and information about their hearts.

Tseng has designed a systematic way of looking at the heart to analyze factors such as scarring, weight and thickness of heart walls, and the presence of other conditions, including diseases of the heart valves. Information from autopsies previously performed by the medical examiner's office on individuals who died from causes not related to the heart, such as falls or car accidents, will be compared against the SCD data.

The World Health Association defines SCD as collapse within one hour of symptom onset, if witnessed, or within 24 hours of having last been seen, if not witnessed. Tseng hypothesized that the very definition of SCD is inaccurate, allowing deaths from unknown causes — such as hemorrhage, vascular aneurysm or stroke — to be lumped into the sudden-death category by physicians filling out death certificates.

Knowing the actual cause of death is critical, according to Tseng, because medical responses such as defibrillators can help prevent SCD for someone prone to cardiac arrhythmias, but will not help a patient with a heart valve malfunction, for example.

"Until we know what we're dealing with, we can't apply our treatments properly," Tseng said. The team also hopes that the SCD research effort will encourage community physicians to order autopsies when faced with possible SCD cases — only then will answers about the little-known disease come to light.

About UCSF Medical Center

UCSF Medical Center consistently ranks as one of the top 10 hospitals in the United States. Recognized for innovative treatments, advanced technology, collaboration among health care professionals and scientists, and a highly compassionate patient care team, UCSF Medical Center serves as the academic medical center of the University of California, San Francisco. The medical center's nationally preeminent programs include children's health, the brain and nervous system, organ transplantation, women's health and cancer. It operates as a self-supporting enterprise within UCSF and generates its own revenues to cover the operating costs of providing patient care.

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