By Mary Ellen Egan
You track your blood pressure, sodium and cholesterol. Soon you may have another vital sign to monitor: blood viscosity.
Researchers have spent the last fifty years studying heart disease and stroke by focusing almost exclusively on biochemical enemy agents in the bloodstream–baddies such as cholesterol, salts and triglycerides. The result has been a slew of drugs such as Lipitor and Zocor to lower cholesterol and a heightened awareness of proper nutrition and exercise.
SIX STEPS TO LOWER YOUR BLOOD VISCOSITY:
1. Donate blood regularly.
2. Take an aspirin a day.
3. Drink 10-12 glasses of water a day.
4. Quit smoking.
5. Reduce fat in your diet.
6. Exercise 3 to 4 times a week.
But there's a culprit cardiologists have long overlooked in their fight against heart disease: the thickness of your blood. A mounting body of research suggests that thicker blood roughs up the arteries and causes plaque to form, which can lead to clogged arteries and heart attacks and strokes.
The reason your blood gets thick is aging, genetics and the presence of cholesterols and fats. But heart attacks can strike even those without traditional risk factors such as high cholesterol levels, suggesting that high viscosity is a possible cause.
Yet doctors, unlike car mechanics, have never had a precise way to measure viscosity to prove that thicker blood leads to heart attacks. Current methods require drawing blood and adding anticoagulants, a step that changes blood from its natural state. As a result, doctors have no baseline viscosity number considered "healthy," analogous to a cholesterol count below 200 milligrams per deciliter of blood. Nevertheless, doctors wrote 21 million prescriptions for the anti-coagulant Coumadin (generically known as warfarin), a drug growing 5% a year. But anticoagulants, aspirin included, merely fight blood clotting without solid proof that they thin blood.
But now a new device called the Rheolog , which accurately measures blood viscosity, is heading for the market next year. It is currently in use by a dozen research labs around the U.S. If it takes off, it may vastly improve the science behind blood-thinning drugs and finally shed light on how thicker blood plays a role in heart disease and stroke. The Rheolog is made by Rheologics , a small, privately held firm in Exton, Pa., founded by 52-year-old cardiologist Kenneth Kensey. Five years from now, he says, "doctors will be measuring viscosity along with blood pressure and heart rate."
Dr. David Faxon, chief of cardiology at University of Chicago Hospital and former president of the American Heart Association, began using the device earlier this year to determine the role viscosity may play in clogging or hardening arteries. He is enthusiastic about the promise of Kensey's device but cautions that no one yet knows how close the link is between viscosity and heart disease. "Even if viscosity is a factor," says Faxon, "patients still need to pay attention to their cholesterol and blood pressure levels."
Kensey's Rheolog device improves on older methods by simulating how blood moves through veins and arteries. In the past, a blood sample was put between two metal plates, and then the plates were turned to measure resistance. But researchers had to add an anticoagulant to keep it from clotting after it's out of the body. The anticoagulant changes blood's properties, skewing the data.
Kensey spent 12 years and $11 million coming up with a machine that mimics nature's way. He put up much of the funding by selling chunks of his original $30 million stake in Kensey Nash, a Nasdaq-listed medical device firm he cofounded in 1983. Less than a teaspoonful of blood from a patient is fed into the Rheolog, a toaster-size device with tubing inside. The blood flows up one leg of a U-shaped tube that has been coated with phosphoryl choline, a protein that tricks the blood into thinking it hasn't left the body.
The blood flows down one side of the "U" and up the other, simulating the cardiac cycle. The blood moves very quickly but eventually slows down and then stops. Software measures the blood's speed 10,000 times as it falls, to produce a reading of height versus time to express viscosity. "It is without a doubt the most complicated problem I've ever had to solve," says Kensey, who also invented a device to stop arterial bleeding during surgical procedures.
Eli Lilly and AstraZeneca are interested in using the Rheolog to test their drugs' effects on blood viscosity. Lilly wants to measure the viscosity of postmenopausal women, to see which face the risk of heart disease should they go on estrogen therapy.