Mayo Magazine

Heart Glitches — Explaining Sudden, Unexplained Deaths through Research

A teenager dies suddenly at swim practice and is found floating face-down in the pool. A young mother dies while nursing her 8-week-old daughter. A 3-month-old infant dies during sleep.

These are some examples of the sudden, unexplained deaths that are referred to the Sudden Death Genomics Laboratory at Mayo Clinic Rochester. The lab is directed by Michael J. Ackerman, M.D., Ph.D., a pediatric cardiologist. Dr. Ackerman is an associate professor of medicine, pediatrics and molecular pharmacology at Mayo Clinic College of Medicine. With his diverse background, Dr. Ackerman leads a research team that uses genetics and genomics to identify difficult-todiagnose electrical problems in the heart — the culprit in many of these kinds of deaths.

Reading the genetic blueprint

Researchers at the Sudden Death Genomics Laboratory study how defects in a person's genetic blueprint may contribute to or be the cause of sudden cardiac death. The research focus is on understanding the genetic underpinnings for sudden, unexplained cardiac deaths involving infants, children, adolescents and young adults.

A team of researchers led by Dr. Ackerman first discovered defects in a gene that causes the heart's electrical system to malfunction. In 1999, they reported in the New England Journal of Medicine how this defect might cause the drowning of an otherwise seemingly healthy person. In 2001, Dr. Ackerman's team discovered that this type of genetic defect in the heart's electrical system is responsible for some cases of sudden infant death syndrome (SIDS). The findings were published in the Journal of the American Medical Association.

More recently, Dr. Ackerman's team identified a strong link between a specific genetic heart syndrome and sudden, unexplained deaths occurring in young mothers during the postpartum period — the time following childbirth. The group also discovered defects in a second gene called RYR2 that causes malfunctions in the heart's electrical system and contributes to what were previously considered to be unexplained drownings.

"By harnessing the power from the Human Genome Project, our research team has solved these seemingly inexplicable tragedies through direct genetic evidence," says Dr. Ackerman. "Swimming and genetic glitches in the heart's electrical system appear to be a bad combination, but we need further study to understand why and how this occurs." Dr. Ackerman and his colleagues are working to establish a national registry of unexplained drownings so sudden death investigations can be conducted.

Discovering explanations

Detectives have long used genetic material, such as deoxyribonucleic acid (DNA), to solve crimes. Today, like a scene from the TV shows Quincy or CSI (Crime Scene Investigation), the researchers at Mayo Clinic's Sudden Death Genomics Laboratory apply sleuth-like tenacity in their search for previously hidden genetic clues that might explain some sudden deaths.

Finding an explanation for these types of deaths can help loved ones bring closure to their unanswered questions, but it can also help the family in other ways Identifying other family members who may be at risk of the same disorder is an important outcome of this research work. This information provides a bridge between research and patient care by helping family members understand their own genetics and, in many cases, make important decisions about prevention options.

"We are striving to make sure that the family's silent killer is not lurking in any of the family members left behind. If we know it is there, we can diffuse it," says Dr. Ackerman. "The next great challenge is to catch this genetic killer before it strikes the first time."