A large British study has cast doubt on the benefits of using beta blockers in patients after they have had acute myocardial infarction (MI), at least in those without heart failure.
Researchers studied data from more than 179,000 patients and found no difference in death rates between those who were prescribed the drugs after a heart attack and those who were not.
Historically, beta blockers have been the standard of care for patients with acute myocardial infarction, but this study suggests that UK guidelines to prescribe the drugs to all patients after heart attack — irrespective of whether or not they have heart failure — may need reconsideration.
The researchers stress that this was only an observational study and that a randomised controlled trial would be needed to definitively assess which patients may not need to take the drugs.
In the analysis, which took data from the Myocardial Ischaemia National Audit Project for England and Wales, there were 91,895 patients who had been hospitalised with ST-segment elevation myocardial infarction and 87,915 patients with non ST-segment elevation myocardial infarction.
Most patients in both groups (96.4% and 93.2% respectively) received beta blockers, report the researchers who published their findings in the Journal of the American College of Cardiology
(online, 29 May 2017).
Overall, there were 9,373 deaths and at first the calculations suggested a lower one-year mortality for patients who were given beta blockers. But after adjusting for several factors, the difference was found not to be significant for both types of heart attack.
Study author Chris Gale, professor of cardiovascular medicine at the University of Leeds and consultant cardiologist at York Teaching Hospital Trust, said while the study did not carry sufficient weight to change practice, the findings along with other research suggest more work is needed.
“Evidence for the effectiveness [of beta blockers] predates the modern management of heart attack, such as the advent of revascularisation and the other MI pharmacotherapies, and the historical trials included patients with heart failure or left ventricular dysfunction,” he said.
He added that it was clear that patients with heart failure or left ventricular systolic dysfunction benefited from beta blockers.
Robert Henderson, honorary secretary of the British Cardiovascular Society, said giving everyone a beta blocker after a heart attack had become part of established medical practice but the trials that showed benefit were done before the advent of newer treatment options including primary angioplasty, which had dramatically altered the outcome for patients.
“They conclude we need a randomised controlled trial and I would agree with that. This paper is not going to change practice but it is a pointer towards the need for an RCT.”
He added that while the researchers had done a sophisticated analysis there could be unknown variables that were never measured that could have influenced the outcome.
The British Heart Foundation estimates there are around 950,000 people in the UK who have survived a heart attack.