New heart attack test shows promise for women
"Doctors could spot twice as many heart attacks in women by using a newer, more sensitive blood test," BBC News reports.
In women, for reasons that are unclear, a heart attack often doesn't trigger the symptom most people associate with the condition: severe chest pain, memorably described as like having an elephant sitting on your chest. This can lead to delays in diagnosis, which may impact on clinical outcomes.
A more sensitive blood test has been developed that can help determine if a person with the symptoms of a heart attack has actually had one.
The new test is more sensitive to levels of a protein called troponin, which is released into the bloodstream when there is damage to heart muscle.
The test was used on more than 1,000 people investigated for a suspected heart attack, in addition to the standard diagnostic protocols, such as an electrocardiogram (ECG).
The researchers found if the new test was used alongside standard protocols, the rate of accurate heart attack diagnoses in women would have doubled. The test had less impact on the diagnosis for men.
If the larger studies now underway confirm these results, more women may be identified who have had a heart attack and are therefore in need of preventative strategies, which, as the BBC rightly concluded, could save thousands of lives.
Where did the story come from?
The study was carried out by researchers from the University of Edinburgh, the Royal Infirmary of Edinburgh, Southern General Hospital, St George's Hospital and Medical School, and the University of Minnesota.
It was funded by the British Heart Foundation with support from the legacy of Violet Kemlo. The tests were provided by the US pharmaceutical company Abbott Laboratories, but it is reported they had no role in the study design or analysis.
The study was published in the peer-reviewed British Medical Journal (BMJ) on an open-access basis, so it is free to read online.
The UK media covered the story accurately, and BBC News also provided expert opinion from Professor Peter Weissberg of the British Heart Foundation (BHF).
He reported the BHF are now funding a larger study to confirm the results, and from this it is hoped more women will be identified who could benefit from preventative measures.
However, the media did not discuss the important finding that even after a diagnosis of heart attack has been made, women were not referred for further investigations or treatment as often as men.
This could suggest potential gender inequality in terms of diagnostic and treatment protocols that may need to be investigated further.
What kind of research was this?
This was a cohort study that aimed to see if a more sensitive blood test could improve the diagnosis of a heart attack and help predict who is at risk of having a further heart attack.
The blood test was used in addition to standard investigations for people who presented to hospital with a suspected heart attack.
The results of the test were not given to the doctors, so did not influence their decisions on treatment, prevention or management.
The researchers recorded which people went on to have a heart attack or die in the next 12 months to see if the new blood test was more accurate.
When there is damage to heart muscle, the cells that die release a protein called troponin into the bloodstream. Higher levels of troponin indicate greater damage.
Troponin levels are routinely checked when someone has symptoms of acute coronary syndrome, a medical emergency where the supply of blood suddenly becomes restricted, resulting in damage to the heart.
Acute coronary syndrome includes:
- myocardial infarction (heart attack)
- unstable angina (symptoms and ECG changes, but no increase in troponin levels)
- non-ST-elevation myocardial infarction – a "milder" type of heart attack (though still extremely serious) where there is a partial blockage of the blood supply to the heart (symptoms and increased troponin levels, but no ECG changes)
People with acute coronary syndrome are at risk of having a heart attack or another heart attack, depending on the diagnosis. For example, if unstable angina is left undiagnosed and untreated, the condition can escalate into a heart attack.
What did the research involve?
All adults presenting to Edinburgh Royal Infirmary with suspected acute coronary syndrome were enrolled in the study between August 1 and October 31 2012.
Troponin levels were measured using the standard test as well as the new, more sensitive test. The tests were performed on admission and again six to 12 hours later.
The doctors were not given the results of the new test, so they based their diagnosis and management on the standard troponin test, symptoms, ECG results and other imaging.
The researchers looked at the clinical records from admission to 30 days. They analysed whether the level of troponin in the new test could predict outcomes such as a heart attack or death.
They used a single cut-off level of troponin 26ng/L, and then a higher level for men of 34ng/L and a lower threshold of 16ng/L for women.
They then calculated whether these levels could predict outcomes at 12 months, and adjusted the results to take into account age, kidney function and other medical conditions.
What were the basic results?
In total, 1,126 people attended the hospital with suspected acute coronary syndrome (mean age 66, 55% men).
Test results
A heart attack was diagnosed in:
- 55 women (11%)
- 117 men (19%)
If the new troponin test had been used with the sex-specific cut-offs, twice as many women would have been diagnosed with a heart attack:
- 111 women (22%)
- 131 men (21%)
These additional women had a similar risk of having a heart attack or dying within the next 12 months as women who were diagnosed.
After adjusting the results to take account of age, renal function and diabetes, compared with people with no ECG changes and negative troponin tests, the likelihood of having a heart attack or dying within the next 12 months was:
- six times more likely in women diagnosed with the new test and ECG changes (odds ratio [OR] 6.0, 95% confidence interval [CI] 2.5 to 14.4)
- nearly six times more likely in women diagnosed with the standard test and ECG changes (OR 5.8, 95% CI 2.3 to 14.2)
- just over five times more likely in men diagnosed with the new test and ECG changes (OR 1.5 to 19.9)
- three times more likely in men diagnosed with the standard test and ECG changes (OR 1.1 to 3.8)
The new test would not have missed anyone currently diagnosed with a heart attack.
Management
Women with a diagnosis of heart attack using the standard tests were less likely than men to:
- be referred to a cardiologist (80% women versus 95% men)
- be given statin treatment (60% versus 85%)
- have coronary angiography – imaging of the heart (47% versus 74%)
- have coronary angioplasty – a surgical intervention to reopen the vessels of the heart (29% versus 64%)
Women who would have been diagnosed with a heart attack using the new test and the ECG changes were the least likely to have any further investigations.
How did the researchers interpret the results?
The researchers concluded that, "Although having little effect in men, a high-sensitivity troponin assay with sex-specific diagnostic thresholds may double the diagnosis of myocardial infarction in women, and identify those at high risk of reinfarction [further heart attack] and death."
They go on to say that, "Whether use of sex-specific diagnostic thresholds will improve outcomes and tackle inequalities in the treatment of women with suspected acute coronary syndrome requires urgent attention."
Conclusion
This new study showed how a more sensitive test of troponin levels would have led to a diagnosis of heart attack in double the number of women studied.
The test made less of a difference to the diagnosis for men. This could be because the troponin levels in the standard test were much higher in men than women.
The research also indicates that even with a diagnosis of heart attack, women were less likely to be referred to cardiologists or have any further investigations or treatment, such as a coronary angiography or coronary angioplasty.
The researchers found women who would have been diagnosed with a heart attack with the new test were even less likely to be referred, prescribed a statin, or have vessel surgery, despite having ECG changes.
In both cases, the reasons for this are unclear. It is also not known what other preventative strategies were actually implemented, such as:
- thinning the blood with aspirin
- treating high blood pressure
- optimising the treatment of any comorbid conditions, such as diabetes
- supporting lifestyle changes, including stopping smoking, reducing obesity and inactivity
The reasons for this are not clear. So it is also unclear what difference an increase in diagnosis would make to outcomes if these underlying gender inequalities in heart attack management are not also addressed. Arguably, this issue warrants further investigation.
