The lub-dub of a healthy heart  pg. 2

“Here’s the fantasy,” Barnett says. “If you need a valve, we take your circulating or bone marrow-derived stem cells, have tissue engineers sculpt the right shape and size matrix, grow the cells on the matrix, and give the complete heart valve to the surgeon.

“Wouldn’t that be amazing?”

An outrageous hypothesis

Stitches in Time
A preserved human heart (also pictured on page 23) displays its history: a variation of the extensive Ross procedure, in which surgeons replaced a diseased aortic valve with the heart’s own pulmonary valve. An artificial valve (shown here) was then stitched in its place
Photo by Dean Dixon
It’s the valves in action that give the heart its characteristic lub-dub sound. With each beat, these one-way fibrous doors open and close in a synchronized fashion to keep blood flowing in a forward direction.

The “lub” happens when the mitral and tricuspid valves – the valves separating the atria and ventricles – close. The “dub” corresponds to the closing of the aortic and pulmonary valves.

Valve failure – because of a developmental defect or disease – forces the heart to work harder to compensate for the defective blood flow, leading in many cases to congestive heart failure.

About one in 100 children is born with a congenital heart defect, the leading cause of death in the first year of life.

“Depending on the numbers you use, somewhere between 60 and 80 percent of these kids have an abnormal valve,” says Scott Baldwin, M.D., chief of Pediatric Cardiology at Vanderbilt who, with Barnett, is leading the charge to grow replacement heart valves in the lab. Children with valve defects often require multiple valve replacement surgeries as they grow.

“On the flip side, up to 4 percent of the population over the age of 60 will need to have a valve replaced because it’s calcified and thickened,” Baldwin says. More than 100,000 valve replacement surgeries are performed each year in the United States, according to the American Heart Association.

“Heart valve problems have become epidemic; it’s an important issue,” Baldwin says.

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