"Many patients given beta blockers after a heart attack may not benefit from being on the drugs, suggesting they may be being overprescribed," The Guardian reports.
Beta-blockers are drugs used to regulate the heart by making it beat more slowly and with less force. They are often used in people who have heart failure or are thought to be at risk of heart failure.
A new study has collected data from England and Wales from more than 170,000 people who had a heart attack but did not have heart failure. The researchers wanted to see if beta-blockers improved health outcomes in this set of patients.
The study compared mortality rates between those who were prescribed beta blockers and those who weren't when they were discharged from hospital. Though there were fewer deaths one year later among people prescribed beta blockers (5% vs. 11%), the researchers concluded that beta blockers did not affect risk of death once other risk factors and medications were taken into consideration.
UK medical guidelines recommend that all people who have had a heart attack take beta blockers for at least one year. And those with heart failure are advised to continue treatment indefinitely. The recommendations for people without heart failure may be reviewed in future guideline updates.
However, any future recommendations would need to consider not only this study but other clinical trial evidence. Beta blockers might still have benefits for patients, aside from mortality.
If you have been prescribed beta-blockers you should not stop taking them without first talking to your GP.
Where did the story come from?
The study was carried out by researchers from multiple UK institutions including the University of Leeds, University of Edinburgh, University College London, Bart's Heart Centre London and York Teaching Hospital NHS Foundation Trust as well as institutions in Sweden, France and Spain.
It was funded by the British Heart Foundation.
Generally the media reported the story accurately. However, the dramatic headline of the Mail Online claiming beta blockers "do more harm than good" is unproven as the study did not look at negative outcomes of taking beta blockers.
What kind of research was this?
This was a prospective cohort study looking at whether taking beta blockers reduced mortality in the year following heart attack for people without heart failure or systolic dysfunction (which is a significant risk factor for heart failure but does not usually cause any symptoms).
Beta blockers are among the recommended treatments for people who've had a heart attack. There is good evidence that beta blockers are effective for patients who have had a heart attack and also have heart failure or signs that the left chamber (ventricle) of their heart is unable to pump blood around the body properly.
For this reason, people with heart failure or left ventricular dysfunction are usually advised to continue taking beta blockers long term.
However it is unknown whether people without heart failure gain much from taking beta blockers. If you don't have heart failure, beta blockers are usually only prescribed for one year after a heart attack.
Beta blockers can also have side effects such as dizziness, slow heartbeat, tiredness and cold hands and feet.
A prospective cohort study is a good way of looking at how treatment affects long term health outcomes in a much larger sample than would be feasible in a randomised controlled trial.
What did the research involve?
Researchers looked at 179,810 people who were hospitalised following a heart attack in the UK between 2007 and 2013. They were identified using the national heart attack register in the UK – known as MINAP (Myocardial Ischaemia National Audit Project).
The study aimed to compare people prescribed beta blockers, or not, following a heart attack to look at the effect this had on likelihood of death after one year.
Only people who had a heart attack but did not have heart failure or systolic dysfunction were included.
Beta blocker use was determined by looking at people who had received a beta blocker prescription on discharge from hospital.
Analyses were carried out and then adjusted for the following confounders:
- socioeconomic deprivation
- year of hospital admission
- cardiovascular risk factors (diabetes, high cholesterol, high blood pressure, smoking status, family history of coronary heart disease)
- chronic obstructive pulmonary disease
- peripheral vascular disease (a condition that restricts blood flow to the limbs)
- discharge medications (including statins, aspirin, and angiotensin-converting enzyme inhibitors)
- adjusted mini-Global Registry of Acute Coronary Events risk score variables (age, cardiac arrest, blood pressure and heart rate at hospitalisation and whether heart enzymes were elevated)
- care by a cardiologist
The earliest hospital record was used for those with multiple admissions. The main outcome was death from any cause one year after hospitalisation.
What were the basic results?
Of the 179,810 people who survived a heart attack during this period, 9,373 died within a year of their initial hospitalisation.
94.8% of all survivors received beta-blockers when they were discharged from hospital. People who received beta blockers were more likely to be male (71% versus 62%), slightly younger (63 years versus 69 years), and less likely to have other medical illnesses like diabetes, kidney failure, history of stroke or asthma (a contraindication to beta blockers).
Looking at the raw numbers, after one year, fewer people had died among those who were prescribed beta-blockers (4.9%) than among those who didn't take the drugs (11.2%). However, with adjustment for confounding factors there was no significant link between beta-blockers and survival at one month, six months or one year.
There was no difference in effect depending on whether or not people had a heart attack with the classical heart attack features on electrocardiogram (ECG, showing elevation of the ST segment).
How did the researchers interpret the results?
The researchers conclude that "among survivors of hospitalization with heart attack who did not have heart failure or left ventricular systolic dysfunction as recorded in the hospital, the use of beta blockers was not associated with a lower risk of death at any time point up to 1 year."
This study aimed to see whether beta blockers reduce mortality in people who've had a heart attack but who don't have heart failure or systolic dysfunction. It found no difference between those who were and those who were not given beta-blockers on discharge from hospital.
The authors say this adds to the evidence that routine prescription of beta blockers might not be needed for patients without heart failure following a heart attack.
Current UK guidelines recommend all people who have had a heart attack take beta blockers for at least one year to reduce risk of recurrent events. Only people with heart failure or left ventricular dysfunction are advised to continue treatment beyond one year.
However, these results suggest that even one year of treatment may not be necessary for all people.
This cohort study benefits from analysis of a large number of people from England and Wales who had a heart attack using reliable national registers. However, there are a number of points to highlight:
- Only data on heart failure within the hospital was examined. People may have been diagnosed with heart failure or left ventricular dysfunction following discharge, therefore the cohort might have included some people with additional indications for beta blockers.
- Beta-blocker use was only measured according to prescription at discharge from hospital. People may have not actually taken the medication as prescribed. A study that better assessed for adherence to beta-blockers throughout the year could give more reliable indication of a benefit.
- There were differences in the characteristics of people taking and not taking beta-blockers. Even though some of these characteristics were adjusted for, there are others that may have had an effect on results, or even treatment compliance, such as education, diet and alcohol intake.
- With any cohort study, even with careful adjustment for other medications and risk factors, it is difficult to be certain that you have isolated the direct effect of beta blockers alone, rather than the combined effect with other medications.
- The study only looked at the effect of death after one year. There may be differences in mortality after one year. There might also be other outcomes, such as risk of re-hospitalisation and heart-related illnesses or interventions (such as revascularisation procedures) that are influenced by taking beta blockers, not just death.
This study contributes a large body of data to the question of whether beta blockers improve outcomes for all people following heart attack. Currently it's not possible to say whether or not these findings will have an effect on treatment recommendations in future guideline updates.
The findings will need to be considered alongside other clinical evidence on the effect of beta blockers in people without heart failure who have had a heart attack, including any randomised controlled trials that have been carried out.
Most people who take beta-blockers experience no or very mild side-effects. But if the medication is causing you problems talk to your GP. Don't suddenly stop taking beta-blockers as this could make your condition much worse.