Gene test that could save lives of heart operation patients
Doctors and scientists have developed a new screening programme to identify those at risk
Doctors have developed a new test to identify patients at risk of complications following heart surgery.
More than 120,000 people undergo coronary artery procedures a year including heart surgery and angioplasty (where a tiny balloon is inserted into the blocked artery to clear it).
Following these procedures, it’s vital that patients take blood-thinning drugs to prevent the formation of blood clots which can cause a new heart attack or stroke.
Clopidogrel, also known as Plavix, is one of the most commonly prescribed clot-busting drugs.
However, to prevent blood clots forming, the drug has to be turned into its active form in the liver.
Recent studies show that about a third of patients have a genetic defect which prevents clopidogrel from working properly, leaving them three to five times more likely to die from a stroke or heart attack within a year of surgery.
Now doctors and scientists at London Bridge Hospital have developed a new screening programme to identify those at risk.
This tests patients’ blood to make sure it is clotting properly and screens for the genetic defect using a swab from the inside of the cheek.
Results are available in less than an hour and, if a problem is found, patients are put on alternative medication.
Currently, patients undergoing heart surgery are monitored for side-effects of the drugs.
Alan Rayner, a surgical assistant who operates the heart-lung machine during surgery, developed the programme alongside cardiologist Dr Cliff Bucknall and says routinely screening all patients requiring coronary intervention will save lives.
‘Until now, patients have been given clopidogrel with no monitoring of its effect. It’s been a one-size-fits-all approach,’ he says.
‘In many cases, the first time doctors are aware that it is not working properly is when a patient gets symptoms such as chest pain.
‘For some, waiting until then may be too late.
‘/12/06/article-2070418-0588B9CA000005DC-594_468x370.jpg” width=”468″ height=”370″ alt=”Research carried out in New Zealand found that preventing just two heart attacks would more than pay for 100 patients to be screened” class=”blkBorder” />
Research carried out in New Zealand found that preventing just two heart attacks would more than pay for 100 patients to be screened
Similar tests are available in other private hospitals and on the NHS.
However, they are not routinely offered to heart surgery patients and the results can take weeks.
The older technology they use means the blood samples have to be sent to specialist laboratories for analysis — and cost at least 500.
Instead, patients are monitored for signs — such as high blood pressure or bleeding after treatment — that the drugs are not working properly. The new test costs around 200.
Research carried out in New Zealand found that preventing just two heart attacks would more than pay for 100 patients to be screened.
But says Professor Jeremy Pearson, associate medical director at the British Heart Foundation, there is not yet enough evidence for the new test to be made available nationwide, as it is not clear how many side-effects the tests would avoid.
‘The principle is a good idea and this kind of personalised genetic testing will increase in the future,’ he says.
‘But there is controversy over whether these tests are cost-effective.’
Meanwhile, a study of 1,000 patients by U.S. scientists has revealed that early-morning heart attacks — those that occur between 1am and 5am — are the most damaging.
The research team, who also factored in the amount of time it took each patient to seek help, suggest that the ability of the heart to protect itself against damage fluctuates with our 24-hour body clock.
These powers of protection are at their lowest between 1am and 5am, as this is when we are in deep sleep; the heart does not need to prepare for any stresses, and so it can reduce the number of protective chemicals and focus on repair.
‘It is important to understand that the heart’s ability to protect itself against more severe damage varies over a 24-hour cycle,’ said the study’s author Jay Traverse, a cardiologist at the Minneapolis Heart Institute Foundation, whose findings were published in the journal Circulation Research.
He believes the findings may help researchers develop more effective heart drugs.