Study: Overly narrow heart valves can break down blood's clotting ability

Thursday, July 24th 2003, 12:00 am

By: News On 6

Blood that passes through overly narrow heart valves may have some of its clotting ability squeezed out of it, leading to internal bleeding or bleeding through the skin, a study reports.

If additional research backs up the finding published Thursday in the New England Journal of Medicine, it could give doctors more reason to order valve replacement surgery for patients with aortic stenosis _ a condition that causes weakness, dizziness and shortness of breath.

Researchers looked at 50 consecutive patients sent to a cardiac hospital in Lille, France, for evaluation of aortic stenosis. Forty-two of them _ 18 women and 24 men _ had a problem serious enough for surgery.

Nine of those 42 patients, or 21 percent, had bleeding episodes unrelated to anticoagulant therapy during the previous six months, Dr. Andre Vincentelli of the University of Lille's medical school reported.

He began his study after other researchers suggested that bleeding problems could be caused when a rush of blood through a tight space squeezes large clotting molecules called von Willebrand factors. That squishing exposes a spot vulnerable to an enzyme that slices the molecules apart, reducing their ability to clot.

Vincentelli reported that most of the nine patients with bleeding problems also had very low amounts of the largest forms of von Willebrand molecules.

That changed within hours after surgery, he wrote.

None of 38 patients reached six months later had had any bleeding problems, Vincentelli wrote. He said that was true even for patients who had bleeding problems before the operation and had to take oral anticoagulants afterward because they had received mechanical valves, which are vulnerable to blood clots.

Aortic stenosis affects an estimated five in 10,000 people, so this form of acquired von Willebrand disease might affect more than 29,000 Americans.

The study does not suggest new ways of treating the more common inherited form of von Willebrand disease, which affects about one person in 50.

Symptoms include easy bruising, heavy or prolonged menstrual bleeding, frequent or sustained nosebleeds, and protracted bleeding after injury, surgery, childbirth or dental work.