Beta blockers may be doing heart attack patients more harm than good, according to new research. The pills, which reduce blood pressure, don't improve survival chances for those who have suffered heart failure, suggest the findings.
Experts called for large randomised clinical trials to see whether they should continue to be taken. Corresponding author Dr Gorav Batra, of Uppsala University, Sweden, said: "In this large nationwide cohort study, long-term beta blocker therapy beyond the first year of heart attack was not associated with lower risk of cardiovascular outcomes in patients without heart failure."
Beta blockers were one of the most commonly prescribed blood-pressure drugs in past decades. But they fell out of favour as newer tablets which appeared to be better at reducing blood pressure became available.
They help widen veins and arteries to improve blood flow. They can also help manage symptoms of anxiety such as a racing heart rate. The tablets work by blocking stress hormones like adrenaline. But they can also cause side effects - including dizziness and tiredness.
They are known to be a useful medication for people with heart failure - a condition that often follows a heart attack, in which the muscle of the heart has become damaged and the ability to pump blood around the body is lowered. But the researchers found that for people who had suffered a heart attack but did not have heart failure, beta blockers made no difference.
Dr Batra said: "The accepted clinical practice of using beta blockers over the long term to curb the risk of further heart attacks or death doesn't seem to be warranted in patients who don’t have heart failure." His team found no difference between patients taking them more than a year after their heart attack and those who weren't on the drugs.
Beta blockers are predominantly used to manage abnormal heart rhythms, as well as angina. They are routinely prescribed after a heart attack to lower the risk of recurrence and other cardiovascular complications–a practice referred to as secondary prevention.
But it's not clear if these drugs are warranted in patients who don't have heart failure, or a potentially fatal complication known as LVSD (left ventricular systolic dysfunction) beyond the first year. Most current evidence is based on the results of clinical trials that predate major changes to the routine care of heart attack patients.
The study in Heart analysed 43,618 older men and women in Sweden who had had a heart attack between 2005 and 2016 that required hospital treatment, and whose details had been entered into a national health database. They were tracked for an average of four and a half years. None had heart failure or LVSD - with 34,253 still on beta blockers a year after discharge and the remaining 9,365 never prescribed them.
Findings showed long-term treatment with beta blockers wasn't associated with improved cardiovascular outcomes. This was after accounting for potentially aggravating factors such as demographics and other illnesses.
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Dr Batra said the study is the largest and most comprehensive of its kind. He explained: "Among 43,618 patients, long-term beta blocker therapy was not associated with improved cardiovascular outcomes
"Until recently, no randomised clinical trial had tested the efficacy of beta blockers on long-term cardiovascular outcomes among patients with herat attack without heart failure or LVSD." Some 6,475 (19 per cent) of those on beta blockers, and 2,028 (22 per cent) of those who weren't, died from any cause, or had another heart attack, or required unscheduled revascularisation, or were admitted to hospital for heart failure.
Dr Batra added: "The results of ongoing randomised clinical trials will provide much needed evidence about the role of long term beta blocker therapy in this group of patients." Cardiovascular disease is the world's number one killer, claiming almost 18 million lives a year.
Professor Ralph Stewart and Dr Tom Evans, of Green Lane Cardiovascular Services, Auckland, who were not involved in the study, said: "Despite strong evidence that long-term beta-blockers can improve outcomes after heart attack, it has been uncertain whether this benefit applies to lower risk patients who are taking other evidence-based therapies and who have a normal functioning heart.
"Recommendations on the duration of beta blocker therapy are variable or absent because this question was not specifically evaluated in clinical trials. Most patients take daily medications for many years after a heart attack because they believe they are beneficial.
"This study raises an important question directly relevant to the quality of care—do patients with a normal functioning heart benefit from long term beta blocker therapy after heart attack? To answer this question, more evidence from large randomised clinical trials is needed." There are currently an estimated one million heart attack survivors in the UK.
