FASD: Heart defects caused by altered function, not structure?

Recent data shows that more than 500,000 women in the U.S. report drinking during pregnancy, with about 20 percent of this population admitting to binge drinking.

Even one episode of heavy drinking can lead to the collection of birth defects known as fetal alcohol syndrome (FAS).

Along with growth retardation, head and face abnormalities, and neurological problems, FAS also causes heart problems in just over half of those with this condition.

Though much research has focused on looking for the cause of these alcohol-induced heart defects, they remain largely a mystery.

To investigate this question, Ganga Karunamuni of Case Western University and her colleagues studied heart formation in quail embryos, whose heart development is very similar to that of humans.

The researchers used an innovative imaging technique, optical coherence tomography, to compare embryos exposed to a single, large dose of alcohol to those who hadn't received alcohol.

They looked both at how alcohol changed the function of the developing hearts as well as their structure.

They found that significant changes in heart function appeared to come well before changes in structure that are hallmarks of the well-known FAS heart anomalies.

These changes in function, the study authors suggest, might be the cause of the structural problems that arise later by exerting forces on the heart that change its development.

The article is entitled "Ethanol Exposure Alters Early Cardiac Function in the Looping Heart: A Mechanism for Congenital Heart Defects?"

It appears in the Articles in Press section of the American Journal of Physiology – Heart and Circulatory Physiology, published by the American Physiological Society.

Results
As expected, the researchers found that the hearts of embryos exposed to alcohol had dramatic defects close to hatching, including thinner walls separating the heart's four chambers and damaged valves.

Long before these defects formed, the researchers saw significant differences in heart blood flow between embryos that weren't exposed to alcohol and those that were.

In those whose shells weren't injected with alcohol, a small portion of the blood flowed backward through the heart circuit after each beat.

In those exposed to alcohol, a much larger portion of blood flowed backward in the circuit.

These malfunctioning hearts had smaller "cardiac cushions"—collections of cells that later become chamber walls and valves—compared to unexposed hearts.

More information: ajpheart.physiology.org