Family Tree Helps Define Risk of Sudden Death

It may be easier to treat arrhythmias that have a genetic component now that Dutch researchers have estimated the ages associated with the highest risk of sudden death.

For example, a severely increased mortality risk for long QT syndrome type 1 (LQTS1), a condition related to sudden infant death syndrome, was seen during all years of childhood but was particularly severe during the first 10 years of life, Eline A. Nannenberg, MD, of Academic Medical Center in Amsterdam, and colleagues reported.

For two other mutations that cause this syndrome (LQTS2 and LQTS3), the risk of death began to increase in the mid-teenage years, but only in LQTS2 did it reach significance from ages 30 to 39, the researchers wrote online in Circulation: Cardiovascular Genetics.

In all, Nannenberg and colleagues examined six inherited arrhythmia syndromes that are caused by specific mutations. Children of parents who carry a mutation have a 50% chance of inheriting it. Although these mutations are rare, the risk of death is high for carriers.

Researchers suggested their findings can be used as a guide to screening families with known genetic mutations. This can facilitate treatment before symptoms associated with arrhythmias arise.

They acknowledged the known "substantial" risk of sudden death in symptomatic untreated patients but said the risk in asymptomatic mutation carriers is less clear.

To determine the optimal genetic and cardiologic screening strategies, researchers need data on the natural history of the disease.

Sudden infant death syndrome (also known as SIDS) is defined as the sudden death of an infant younger than 1 year of age. If the child's death remains unexplained after a formal investigation into the circumstances of the death (including performance of a complete autopsy, examination of the death scene, and review of the clinical history), the death is then attributed to SIDS. Sudden infant death is a tragic event for any parent or caregiver.

• SIDS is suspected when a previously healthy infant, usually younger than 6 months of age, is found dead in bed. In most cases, no sign of distress is identifiable. The baby typically feeds normally prior to being placed in bed to sleep. The infant is then discovered lifeless, without pulse or respiration. Cardiopulmonary resuscitation (CPR) may be initiated at the scene, but evidence shows a lack of beneficial effect from CPR. The cause of death remains unknown despite a careful review of the medical history, scene investigation, X-rays, and autopsy. - SIDS is rare during the first month of life. Risk peaks in infants 2-4 months of age and then declines. - About 90% of SIDS deaths occur in infants younger than 6 months of age.
• Even though the specific cause (or causes) of SIDS remains unknown, scientific efforts have eliminated several previously held theories. We now know the following about SIDS: - Apnea (cessation of breathing) of prematurity and apnea of infancy are felt to be clinical conditions that are distinct from SIDS. Infants with apnea may be managed with electronic monitors prescribed by doctors that track heart rate and respiratory activity. Apnea monitors will not prevent SIDS. - SIDS is not predictable or preventable. - Infants may experience episodes termed apparent life-threatening events (ALTEs). These are clinical events in which young infants may experience abrupt changes in breathing, color, or muscle tone. Common causes of ALTEs include viral respiratory infection (RSV), gastroesophageal reflux disease, or seizure. However, no definite scientific evidence links ALTEs as events that may lead to SIDS. - SIDS is not caused by immunizations or bad parenting. - SIDS is not contagious or hereditary. - SIDS is not anyone's fault.