"Early warning signs may have been missed in up to one in six people who died of a heart attack in English hospitals," BBC News reports.
A review of hospital records found 16% of people who died of a heart attack were admitted in the previous 28 days with another condition.
The study authors say this raises the possibility that doctors missed early warning signs of heart attack in people who were being admitted with other heart problems, lung disease or an injury, such as a broken hip.
The researchers argued that more research needs to be done to establish whether these admissions could represent opportunities to reduce the numbers of deaths from heart attack.
A fact largely ignored by media reports is that half of people who died of a heart attack had not been admitted to hospital. This underlines the importance of getting help quickly when heart attack symptoms start.
Symptoms of a heart attack can include:
Not everyone has severe chest pain – the pain can often be mild and mistaken for indigestion. The important thing to focus on is the overall pattern of symptoms.
A heart attack is a medical emergency. Dial 999 and ask for an ambulance if you suspect a heart attack.
The study was carried out by researchers from Imperial College London and Harvard Medical School and was funded by the Wellcome Trust, Medical Research Council, Public Health England and National Institute of Health Research. The study was published in the peer-reviewed journal The Lancet Public Health on an open-access basis, meaning it is free to read online.
Two of the authors reported links with the pharmaceutical industry, but there were no apparent conflicts of interest.
Most of the UK media say that the study found that doctors had missed warning signs of one in six fatal heart attacks. However, the study didn't show that for certain.
It found that 16% of people who'd died of a heart attack had been treated in hospital for other conditions, but that doesn't mean warning signs were definitely missed.
We don't know the individual circumstances of the cases – for example, whether people had tests for heart attack, or whether the condition was considered but ruled out.
The researchers say that additional study is needed to find out "whether these admissions represent missed opportunities" for the treatment of people with impending heart attack.
This is a record linkage study that looked at data on deaths from heart attacks from the Office for National Statistics (ONS)
Researchers then linked that to data on hospital episode statistics, to see whether these people had been admitted to hospital in the past 28 days, and if so what they had been diagnosed with and treated for.
The study can show patterns, such as how many people who died of heart attack had been previously diagnosed with heart attack.
But it can't tell us the detail about each case, so we don't know how the diagnosis on admission was linked to the person's eventual death.
Researchers looked at data on deaths from heart attack in England between 2006 and 2010 (158,711 deaths), and at hospital episode statistics for the same period, which record hospital admissions, diagnoses and deaths. They linked the data to look for patterns between diagnoses (either at first admission, or later during the hospital stay), and eventual death from heart attack. They wanted to know whether the patient's initial diagnosis made a difference to how likely they were to die of heart attack.
Data on deaths came from the ONS.
This data records all deaths in England and the underlying cause. Hospital episode statistics data came from the Health & Social Care Information Centre (now known as NHS Digital). The data records each "episode of care" when someone is admitted to hospital, including the diagnosis made by each doctor whose care they come under.
Doctors can record one diagnosis, or one primary diagnosis with several co-morbidities – for example, someone might have pneumonia as a primary diagnosis, and heart arrhythmia (irregular rhythm) as a co-morbidity.
Researchers linked the data in a "follow-back and follow-forward" study, tracing what happened to people after an admission to hospital, as well as back from a death from heart attack. They stratified the data by age and sex, as men and women – and older people – may experience heart attacks differently.
The researchers found that just over half the people who died of a heart attack (51%) had not been admitted to hospital in the 28 days before their fatal heart attack. Among the remaining 49%, who had been admitted to hospital:
People whose heart attack diagnosis was made alongside that of another illness were two to three times more likely to die of heart attack than those who were just admitted with a heart attack.
The most common diagnoses among people who were admitted for conditions other than a heart attack, but subsequently died of heart attack, were:
The researchers say their results show the "underinvestigated role" of fatal heart attacks when people have been admitted to hospital with no diagnosis of heart attack, or with heart attack mentioned as a "co-morbidity" alongside another condition. They say their records "often" include mention of risk factors or symptoms "which might herald the impending death from acute myocardial infarction [heart attack]".
However, they say more research needs to be done to establish whether these admissions could represent opportunities to reduce the numbers of deaths from heart attack.
They point to the 51% of heart attack deaths that happen outside hospital, with no recent admission, and say that the time between getting symptoms and calling for help "has changed little since the 1980s".
They say that shortening the delay in getting people with heart attacks to hospital "could result in substantial improvements" for these people.
They also look at why people with more than one condition might be more likely to die of a heart attack. They say that these patients are often older, often women, and that the heart attack may be prompted by a "stressor condition" such as pneumonia or a broken hip. Rather than causing a standard heart attack, this causes a different type, known as type 2. They say the best management of type 2 heart attacks is "currently uncertain".
Are doctors missing signs of heart attack in people admitted to hospital? The study results show that may be true in some cases, but there could be other explanations for these findings.
One limitation of the study is that it doesn't show what tests were done, so we don't know whether people who'd complained of chest pain, for example, had tests for heart attacks. We don't know whether doctors actually missed the signs, or whether they investigated them but the tests were negative.
It's also possible that – where people were admitted for one reason but eventually died of a heart attack – the initial diagnosis was the one most important to treat at the time.
The point is that heart attacks brought on by other conditions are not easy to treat. Often very ill patients can have two or more chronic diseases (co-morbidities), which can trigger a range of interrelated complications.
This issue of co-morbidities may also explain why people who had heart attacks as well as other conditions were more likely to die than those who had heart attack only. People with several conditions were also more likely to be frail and elderly, so less likely to survive a heart attack.
While the study has a clear message for doctors – that possible signs of heart attack should always be looked for and risks acted on – there's also an important message for the rest of us.
More than half of people who died of a heart attack didn't make it to hospital. Knowing the signs of a heart attack, and getting help quickly, is the key message for most people from this study.
Symptoms of a heart attack can include:
If in doubt, it is far better to err on the side of caution. Call 999 for an ambulance.