Studies that started in an Amsterdam emergency room have yielded the first molecular insight into cardiac conduction disease-a disorder that slows the heart rhythm, necessitating pacemaker implantation in millions worldwide.

Cardiac conduction disease tends to afflict older patients, not young children like the three-year-old whose episodes of fainting during a feverish illness brought her family to the front lines of genetic research. The child and several other members of her family, it turns out, have a genetic mutation that causes cardiac conduction disease.

Scientists collaborating across the Atlantic describe the mutation and how it slows the cardiac rhythm in the February 22nd issue of Nature.

"Before this family came to medical attention, we had little insight into the molecular mechanisms that could potentially contribute to acquired conduction disease-the type that affects people as they age," said the report's senior author, Dr. Jeffrey R. Balser, associate professor of Anesthesiology and Pharmacology and holder of the James Tayloe Gwathmey Physician-Scientist Chair at Vanderbilt University. "We hope that this newly defined genetic mutation will serve as a model for understanding what's happening in aging hearts."

The child brought to the emergency room for fainting was suffering periods of a very slow heart rate-25 beats per minute instead of the normal 120 beats per minute for a child her age. The conduction disturbance persisted after the acute illness had ended, and her physicians ruled out other causes, including structural heart disease, viral infections, auto-immune disease, and thyroid dysfunction. The child required a pacemaker to regulate her heart rhythm.

Subsequent examination of family members revealed nearly identical findings in an older sister, who also required pacemaker implantation, and evidence of slowed conduction in three adults.

All of the affected family members have a genetic mutation that alters the acti
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Contact: Leigh MacMillan
leigh.macmillan@mcmail.vanderbilt.edu
615-322-4747
Vanderbilt University Medical Center
21-Feb-2001