New blood test may lead to better predictions of heart attack risk

A compound produced in the gut is a reliable indicator of major heart problems in patients arriving at A&E, according to a report in the European Heart Journal.

Researchers in Switzerland and the US have found that by measuring levels of a molecule called trimethylamine N-oxide or TMAO (which is produced by the gut bacteria from components of red meat, eggs and diary) they can accurately establish the risk of serious heart problems and death, both in the short term and for up to seven years.

The standard diagnostic test, for a protein called troponin T that is usually released when the heart muscle has been damaged, does not work in every case because some people do not have it in their blood. The new test would be similarly inadequate in those who don’t eat meat, eggs and dairy.

The findings suggest patients could reduce their risk by lowering TMAO levels in two ways: through a change in diet or by designing new drugs that prevent TMAO being produced.

Professor Thomas Lüscher, the study’s lead author, said: ‘We found that the Cleveland patients with higher TMAO levels were more likely to experience a major adverse cardiovascular event at 30 days, six months and seven years after their admittance to hospital [with chest pain].

‘After adjusting for risk factors such as age, smoking, diabetes, cholesterol levels and blood pressure, when compared with patients with the lowest TMAO levels, those with levels in the top 25 per cent were around six times more likely to die, suffer a heart attack or stroke or require revascularisation at 30 days and six months, and nearly twice as likely to die within seven years.

‘Interestingly, even in patients who did not appear to have elevated levels of troponin T when they first arrived at hospital, those with the TMAO levels in the top 25 per cent still had a nearly six-fold higher risk of a major adverse cardiovascular event.

‘In the larger group of Swiss patients, those with the highest TMAO levels had a 1.5 times higher risk after one year, after adjusting for other risk factors. Possibly this is related to different dietary habits of Swiss and US patients.

‘This study shows for the first time that TMAO levels are associated with both short- and long-term risks of death and other cardiovascular problems among patients coming to hospital emergency departments with chest pain and suspected heart problems.

‘We think that rapid TMAO testing could now contribute to the identification of higher risk patients, with the potential to speed up the time between initial evaluation and cardiac catheterisation. This could help salvage more of the heart muscle that is under stress, as time is muscle.’

Instant analysis
Patients who present with chest pain are usually swiftly assessed as to whether they may be having a heart attack, and one of the tests commonly used in the UK measures a protein in their blood that can indicate damage to heart cells.

This study suggests there may be an even more sensitive test now available where the levels of a molecule called TMAO, produced by gut bacteria, can estimate the likelihood that someone with chest pains will suffer a heart attack within a month, six months or seven years. This would allow for high-risk patients to have heart scans, stents fitted if required and change their lifestyle to reduce their heart risks. High levels of TMAO are associated with blood vessel inflammation and clots.

The test, which would cost around £45, is currently not in use in the UK and cardiologists here are still quite a way off from deciding if this adds value to the existing clinical pathways that patients with chest pain currently follow. So, this is an interesting study, but do not expect to be offered the test in your local hospital any time soon.
RH
Research score: 4/5