Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Clot-busting drugs may help detect potentially

15.02.2005


A possible diagnostic use for clot-dissolving drugs such as tPA has been found by Medical College of Georgia researchers working to improve a test that identifies potentially deadly blood clots in the legs.



“This study is a fairly simple concept,” says Dr. Vincent J.B. Robinson, nuclear cardiologist at MCG and the Veterans Affairs Medical Center in Augusta and lead author of a study in the February issue of CHEST detailing how clot-busting drugs such as tPA, already used to treat strokes and heart attacks, may help find clots as well.

When patients go to their doctor with symptoms such as swollen legs with tender spots, shortness of breath or passing out, they may get a simple blood test called the latex d-dimer, says Dr. Robinson.


The d-dimer test is a screening test that checks the blood for evidence that the body is trying to break down a clot. The body forms blood clots, impermeable masses of elastic fibrin and platelets and other cells, to stop bleeding. But clots also can form for no apparent good reason, particularly in areas such as the legs where blood pools.

“It’s just how we are built; dependency and immobility shifts the balance to clotting inside our veins,” says Dr. Robinson. This risk is the main reason flight attendants remind passengers to stretch their legs on long flights and hospitals put intermittent inflatable devices on the legs of bedridden patients. Some people have an inherited predisposition to forms these clots, a condition called thrombophilia.

Each year, 250,000 hospitalizations and 200,000 deaths in the United States result from these clots moving to the lungs, where they can prevent sufficient oxygen from getting to the body, the researchers says. About 10 percent of hospital deaths are linked to the potentially preventable scenario of clots forming in the venous system, then breaking loose.

Amazingly, the body already has tPA in the lining of blood vessels to help dissolve clots; the d-dimer tests looks for the breakdown products of that effort. While the standard d-dimer test has been shown highly efficient at detecting a clot once it has reached the lungs, called a pulmonary embolism, it’s not as efficient at finding clots deep in the leg veins where many of them start.

MCG researchers, led by Dr. Robinson, wondered if they could improve the effectiveness of clot detection by giving small amounts of tPA before the test.

They hypothesized that the lower part of the legs has lower rates of clot dissolution because a clot large enough to occlude a vessel in the leg would minimize contact between the clot and the blood.

Using pigs as their animal model, the researchers first performed d-dimer studies to get a baseline, then caused a clot in the femoral vein in the groin. An hour later, there were no significant changes in the d-dimer levels even though, if the natural clot-busters were working as might be expected, the levels should have risen rapidly.

So they gave five progressively higher doses of tPA – the highest of which was well below the therapeutic level given for stroke or heart attack treatment – and d-dimer levels increased within 30 minutes of each dose, with significant changes at the highest two doses.

“There are some groups of people, especially those with deep-vein thrombosis in their lower limbs, who don’t show positive with the standard d-dimer test. How can we improve the ability of the d-dimer test to detect clots in these groups? The answer may be to add a miniscule dose of tPA so that it would break down a small amount of the clot,” says Dr. Robinson. “There is also a group of patients who are false positive. I had one in my clinic today. Those people have higher levels of d-dimer and we don’t know why. It may be they have confounders, such as antibodies that mimic d-dimers,” says Dr. Robinson.

Adding tPA or some other clot-dissolving drug right before the test may clear up those positives and negatives, he says, hypothesizing that measuring the difference between the standard and the new ‘provoked’ d-dimer test will allow the clinician to better determine whether the clot was present in the first instance.

A better d-dimer test also could help some patients avoid more costly and potentially more risky tests, such as a computerized tomography scan with a radiographic dye, he says.

Dr. Robinson recently applied for an American Heart Association grant to fund clinical studies in which humans get two d-dimer tests: one without tPA and the second after a tiny dose. “Then, we may have a gold standard technique for looking at clots in people which will work for nearly everyone.”

Co-authors on the study include Dr. Guillermo E. Pineda, former MCG cardiology fellow who is now on the faculty at the University of South Carolina in Columbia; Dr. Ali K. Salah, MCG internal medicine resident; Dr. Walter L. Pipkin, former MCG general surgery and vascular surgery fellow who is now a pediatric vascular surgery fellow at the University of Alabama; James H. Corley, nuclear pharmacist and associate professor of radiology at MCG; Mary H. Jonah, supervisor of the MCG Hematology Lab in the Department of Pathology; and Dr. James R. Gossage, MCG pulmonologist.

Toni Baker | EurekAlert!
Further information:
http://www.mcg.edu

More articles from Health and Medicine:

nachricht Collagen nanofibrils in mammalian tissues get stronger with exercise
14.12.2018 | University of Illinois College of Engineering

nachricht New discoveries predict ability to forecast dementia from single molecule
12.12.2018 | UT Southwestern Medical Center

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Data use draining your battery? Tiny device to speed up memory while also saving power

The more objects we make "smart," from watches to entire buildings, the greater the need for these devices to store and retrieve massive amounts of data quickly without consuming too much power.

Millions of new memory cells could be part of a computer chip and provide that speed and energy savings, thanks to the discovery of a previously unobserved...

Im Focus: An energy-efficient way to stay warm: Sew high-tech heating patches to your clothes

Personal patches could reduce energy waste in buildings, Rutgers-led study says

What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes - while significantly reducing your...

Im Focus: Lethal combination: Drug cocktail turns off the juice to cancer cells

A widely used diabetes medication combined with an antihypertensive drug specifically inhibits tumor growth – this was discovered by researchers from the University of Basel’s Biozentrum two years ago. In a follow-up study, recently published in “Cell Reports”, the scientists report that this drug cocktail induces cancer cell death by switching off their energy supply.

The widely used anti-diabetes drug metformin not only reduces blood sugar but also has an anti-cancer effect. However, the metformin dose commonly used in the...

Im Focus: New Foldable Drone Flies through Narrow Holes in Rescue Missions

A research team from the University of Zurich has developed a new drone that can retract its propeller arms in flight and make itself small to fit through narrow gaps and holes. This is particularly useful when searching for victims of natural disasters.

Inspecting a damaged building after an earthquake or during a fire is exactly the kind of job that human rescuers would like drones to do for them. A flying...

Im Focus: Topological material switched off and on for the first time

Key advance for future topological transistors

Over the last decade, there has been much excitement about the discovery, recognised by the Nobel Prize in Physics only two years ago, that there are two types...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

ICTM Conference 2019: Digitization emerges as an engineering trend for turbomachinery construction

12.12.2018 | Event News

New Plastics Economy Investor Forum - Meeting Point for Innovations

10.12.2018 | Event News

EGU 2019 meeting: Media registration now open

06.12.2018 | Event News

 
Latest News

Data use draining your battery? Tiny device to speed up memory while also saving power

14.12.2018 | Power and Electrical Engineering

Tangled magnetic fields power cosmic particle accelerators

14.12.2018 | Physics and Astronomy

In search of missing worlds, Hubble finds a fast evaporating exoplanet

14.12.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>