The research, published online in the journal Thorax, suggests that all patients with abnormal blood vessels in their lungs known as pulmonary arteriovenous malformations (‘pulmonary AVMs’) might benefit from potentially life-saving treatment to block off the malformed blood vessels.
About 4,000 people in the UK are estimated to have pulmonary AVMs. As many as one in three of them will have a stroke or brain abscess by the age of 65, according to the new research.
Until now, treatment has only been available for small numbers of patients in the UK, because its effectiveness at reducing stroke was not proven and it was widely considered that only those already unwell could benefit from it.
The new study is the first to show that treatment lowers the risk of stroke. The authors - researchers and doctors from Imperial College London and Imperial College Healthcare NHS Trust - believe it is important that treatment is offered to all patients and not just to those who are obviously unwell.
The study reveals that seemingly healthy patients, with one or two pulmonary AVMs, have essentially the same risk of stroke as patients who are obviously unwell and have a number of large pulmonary AVMs.
“Our statistical analysis has shown that it doesn’t matter how sick someone is – a pulmonary AVM patient who is fit and well has the same stroke risk as someone who is on oxygen,” said Dr Claire Shovlin, from the National Heart and Lung Institute at Imperial College and lead author of the study.
Pulmonary AVMs are strongly linked to a genetic condition called Hereditary Haemorrhagic Telgangiectasia (HHT), which affects around 1 in 5,000 people in the UK. Most people with HHT are well and are unaware that they have the condition until it is diagnosed in a family member.
The authors of the new study call for screening for pulmonary AVMs to be given to all those with HHT. They say that doctors must not be complacent about the wellbeing of people with HHT just because they appear to be healthy.
“In other parts of the world, it is recommended that people with HHT should be screened for pulmonary AVMs and offered treatment for them. At the moment, relatively few individuals in the UK receive this sort of management,” added Dr Shovlin.
Pulmonary AVMs are a serious risk to patients because the enlarged blood vessels do not do their job of filtering out small clots or infected material circulating in the blood, thus allowing this material to pass into the brain, potentially causing stroke (clots), or brain abscess (infected material).
Pulmonary AVMs can be treated by a procedure known as embolisation, which is performed under local anaesthesia. The new study shows that this procedure is highly effective at preventing stroke in pulmonary AVM patients. All procedures in the study were carried out by Dr James Jackson, an interventional radiologist at Hammersmith Hospital, which is part of Imperial College Healthcare NHS Trust. Dr Jackson is one of the authors of the new research.
For the pulmonary AVM embolisation, the radiologist passes a fine tube through a blood vessel in the top of the leg and then introduces small metallic coils into the malformed blood vessels. The coils block off the blood supply to the malformed blood vessels and force the blood to flow through healthy blood vessels instead, ensuring that the blood is properly filtered.
“We have shown that healthy individuals with pulmonary AVMs may benefit not only from embolisation, but also from other preventative measures, including improving dental hygiene,” said Dr Shovlin.
Improved dental hygiene is important as bacteria from the mouth enter the bloodstream and can pass through pulmonary AVMs and enter the brain.
The cohort study analysed the medical histories of 219 pulmonary AVM patients seen by Dr Shovlin at Hammersmith Hospital from 1999 to 2005. Researchers looked at a huge range of data about the extent of their condition and their general level of health, including the size and number of malformed blood vessels in the lungs, oxygen levels, blood pressure and smoking history. They then compared the data for those patients who had suffered stroke or brain abscess and those who had not.
This study was funded by the Margaret Straker HHT Memorial Fund and donations by families and friends of British HHT patients.
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