Tiny gas bubbles can help identify people at risk of a life-threatening heart attack.
Once injected into the bloodstream, the movement of the bubbles can be monitored with an ultrasound probe. If they slow down or stop, it could indicate that there is a potentially dangerous blockage that needs to be cleared immediately.
A new study testing the technique in four patients by Imperial College London has shown promise.
Many patients admitted to the emergency room with chest pain often discover after a long battery of tests that they do not actually have heart problems
The hope is that the bubble injection could eventually be used in busy emergency departments to quickly identify whether patients with chest pain need urgent treatment to clear a blockage – or if something else is the cause.
More than seven million people in Britain suffer from heart disease, a condition in which the arteries that supply blood to the heart are narrowed or blocked, largely due to a build-up of fatty deposits.
When blood flow to the heart is disrupted, it can lead to acute chest pain, which may indicate a heart attack. This requires urgent medical treatment (for example, with blood-thinning medications, or with a typical metal tube called a stent to open a blockage).
But about half of all patients who arrive at the emergency room with pain do not actually have heart problems.
Instead, their discomfort is often related to other problems, such as severe heartburn, anxiety, or a peptic ulcer – a painful sore in the lining of the stomach or esophagus.
Despite this, most of these patients initially undergo long-term monitoring to rule out a heart attack.
Under current NHS guidelines, patients with a suspected heart attack should have a blood test for a protein called troponin as soon as they arrive at hospital. These ‘cardiac enzymes’ are released in large quantities by the heart muscle as a result of a heart attack.
Then, a second troponin test is performed at least three hours later to verify the results of the first.
Patients are kept under close supervision in the hospital while results are monitored. Only then, after a few hours, are they sent home or referred back to the doctor, when their heart is completely clear.
Those with a high troponin score are usually referred for an angiogram – where a special dye is injected (under local anaesthetic) into the bloodstream and monitored with x-rays as it flows through the body, highlighting any blockages.
The procedure, which was trialled on four people by Imperial College London, involved injecting thousands of bubbles into the bloodstream and then monitoring them with an ultrasound machine
The new test, which takes just a few minutes, could speed up the detection of clogged arteries and free up NHS beds occupied by patients whose pain is not actually heart-related.
In a study at Imperial College London, the technology was tested in four patients with a history of heart disease. For the simple procedure, thousands of bubbles are mixed with a saltwater solution and slowly injected into a vein through a small incision in the patient’s arm.
After a few minutes, a portable ultrasound probe is passed over the patient to monitor the bubbles as they pass through the blood vessels around the heart.
The sound waves bounce back off the bubbles and are converted into a computer image that indicates how well they move through the blood vessels.
The results of the study, published in the journal Nature Biomedical Engineering, showed that the scan picked up all the microscopic bubbles as they navigated through even the smallest arteries.
Separate tests, using pig hearts, also showed that arteries where the bubbles had either slowed, stopped or converged in the center of the vessel (indicating fatty deposits on the walls) were blocked or partially blocked .
Dr. Klaus Witte, a consultant cardiologist at Leeds Teaching Hospitals NHS Trust, says hospitals need faster ways to diagnose heart problems – and this ‘bubble technique could help’ solve the problem
Commenting on the technology, Dr Klaus Witte, a consultant cardiologist at Leeds Teaching Hospitals NHS Trust, said the test is ‘very interesting’.
“More than half of all emergency room visits for chest pain are not due to the heart,” he added.
‘We need a quick and easy way to identify people with a heart problem that could be life-threatening – and this technique could help.’