Many patients given beta blockers after a heart attack may not benefit from being on the drugs, suggesting they may be being over-prescribed, researchers said.
UK medical guidelines recommend all people who have had a heart attack should be put on beta blockers, which are medicines that reduce the activity of the heart and lower blood pressure.
They are necessary for people who have had a heart attack with heart failure, a complication in which the heart muscle is damaged and stops working properly, as they help the heart work more effectively.
But while around 95% of heart attack patients who did not have heart failure are also given beta blockers, the drugs do not help them live longer, research by a team at the University of Leeds suggests.
Not everyone who has their first heart attack has heart failure, and the study, published in the Journal of the American College of Cardiology, focused on patients who did not suffer the complication.
Analysis of anonymous data from the UK's national heart attack register looked at 179,810 people who were hospitalised with a heart attack between 2007 and 2013, but did not suffer heart failure.
It examined whether being put on beta blockers made any difference to their chances of being alive one year on.
The researchers found no statistical difference in death rates within a year of the patients suffering their heart attack between those who had been prescribed beta blockers and those who had not.
It could mean the drugs, which can have side-effects for some patients such as dizziness and tiredness, are being over-prescribed and burdening patients and the NHS with unnecessary medicine costs, the scientists said.
Dr Marlous Hall, lead investigator and senior epidemiologist at the Leeds Institute of Cardiovascular and Metabolic Medicine, said: "If you look at the patients who had a heart attack but not heart failure, there was no difference in survival rates between those who had been prescribed beta blockers and those that had not."
Chris Gale, Professor of Cardiovascular Medicine at the University of Leeds and Consultant Cardiologist at York Teaching Hospital Trust, said: "There is uncertainty in the evidence as to the benefit of beta-blockers for patients with heart attack and who do not have heart failure.
"This study suggests that there may be no mortality advantage associated with the prescription of beta blockers for patients with heart attack and no heart failure."
They said patient trials were needed to back up the findings and examine other issues, such as whether beta blockers prevent future heart attacks, to help "personalise" medications after a heart attack.
The British Heart Foundation, which funded the research, says there are around 950,000 people in the UK who have survived a heart attack.