Thrombosis - a question of clotting

8 May 2015        

Picture of Rachel Sacks from the Research Communications team. Rachel Sacks, from our Research Communications team, looks into BHF breakthroughs in thrombosis and where our research is headed.

You may have noticed that this week was National Thrombosis Week, but what exactly is thrombosis?

Thrombosis is the process by which clotting occurs whenever there is damage to a blood vessel. It involves small cells in the blood called platelets, and proteins which circulate throughout the bloodstream. During clot formation, these platelets and proteins are rapidly stimulated to form a clot in order to plug the site of damage and prevent blood from leaking out of the vessel.

Blood clotting, although critical in healthy healing (it forms the scab when you cut yourself) can also be dangerous…

What have we learnt over the years?

In the 1970s a BHF Professor, Michael Davies, conclusively proved that blood clots in the heart’s coronary arteries can cause heart attacks by starving the heart of blood. 

We now know that blood clots can also cause strokes by cutting off the blood supply to part of the brain, causing brain cells to become damaged or die.

The next step for scientists around the world was to take a look at why and how blood clots happen, and to start developing clot-busting medicines.


Over the next 20 years thanks in part to major BHF-funded studies the clot-busters aspirin and streptokinase, taken as soon as possible after a heart attack or stroke, were proven to reduce deaths. 

This was very exciting for the medical community, and vast changes in doctors’ prescribing patterns were seen (68 per cent of doctors shifted to routine administration of the drugs after a person had a heart attack). 

However these drugs don’t always work effectively, and both can cause an increase in bleeding after injury.

So how much more do we have to find out?

There is still plenty of research to be done into understanding the exact process of clot formation. 

Aspirin works by blocking platelet activation. BHF Professor Steve Watson and his team study in detail how platelets are stimulated to form a clot, in the hope of finding new drugs that can prevent clotting but with reduced risk of bleeding. 

Streptokinase works by dissolving the proteins in the clot. Dr Helen Philippou in Leeds has BHF funding to discover new drugs that prevent the proteins from clotting and which again will reduce the risk of bleeding.

In a different approach, researchers at Washington University School of Medicine have worked to produce new drugs that remove the molecules causing platelet activation. Last year they found that a genetically-engineered protein called APT102 is effective at preventing blood clots from reforming in dogs after a heart attack, and reduces the risk of bleeding.

What do blood clots look like?

A grey background, showing a clot, with multi-coloured cells depicted from a scanning electron microscope

Fraser Macrae from the University of Leeds carries out research to better understand how clots are formed in the body.

Working out the clot structure may be of benefit in the prevention and treatment of heart and circulatory disease.

Fraser Macrae
University of Leeds

His image (shown above) won our annual science image competition ‘Reflections of Research’ in 2014. This picture could easily be mistaken for an underwater coral reef but is, in fact, a detailed microscope image of a blood clot – the leading cause of heart attacks and stroke. The thick grey mesh is the clot, capturing a mixture of different cells seen in different colours.

Researching clotting, saving more lives

Although we have already made huge advances in the prevention and treatment of heart attacks, there is much more to be done. That's why we fund scientists, like BHF Professor Steve Watson, to help us understand more about dangerous blood clots and how we might prevent them causing heart attacks.

All of our research is made possible by you. Help us keep funding breakthroughs.