There was no benefit one year after a heart attack in people without heart failure or left ventricular systolic dysfunction.
Taking beta blockers after a heart attack may not protect against the risk of having another heart attack beyond 12 months, according to new research.
The Swedish study including more than 43,000 older adults who had had a heart attack found that beta-blocker treatment was not associated with improved cardiovascular outcomes if they did not have heart failure or left ventricular systolic dysfunction.
Researchers found that over an average of 4.5 years, recurrent myocardial infarction, unscheduled revascularisation, hospitalisation for heart failure or death occurred in 18.9% of the 34,000 patients on beta-blockers and in 21.7% of the 9300 patients who weren’t.
“After adjustment for demographics, relevant comorbidities and with inverse probability weighting, beta-blockers versus no beta-blockers therapy was associated with a similar rate of the primary composite outcome,” they wrote in Heart.
“The results of our study address an existing gap in the current evidence and provide an insight into long-term optimal secondary prevention strategies for a large proportion of myocardial infarction survivors, namely patients with no heart failure or [left ventricular systolic dysfunction] who may have longer survival compared with those who develop such complications after an MI,” the researchers said.
Cardiologist Professor Andrew Sindone said beta-blockers had the greatest benefits within the critical 12-month period after a myocardial infarction.
After one year, however, the benefits of beta-blockers “start to wear off” in people who are at low risk, the director of the heart failure unit and department of cardiac rehabilitation at Sydney’s Concord Hospital told TMR.
Within the first week, beta-blockers reduced the risk of “cardiac catastrophe” such as a ruptured interventricular septum, ruptured pillory muscle, or ruptured left ventricular free-wall, he said.
“In the first few months it will help control blood pressure, reduce atrial fibrillation and ischaemia,” he said.
“After 12 months, those benefits start to wear off because you’ve got the blood pressure right and everything’s good.”
Professor Sindone said in patients who don’t have hypertension, heart failure, atrial fibrillation or ongoing ischaemia, the benefits of beta blockers were “negligible”.
“And the reason for that is those patients are really low risk, and beta blockers are not a free lunch. They do have side effects.”
Professor Sindone said beta-blockers slightly increased LDL cholesterol and blood glucose levels and caused fatigue.
That’s why “beta blockers in the longer term are not such a great thing”, he said.
This was why the study didn’t show a benefit of taking beta-blockers beyond 12 months, he said.
“It had low-risk patients who’d already been treated with their revascularisation, and the highest risk patients who you would definitely give a beta-blocker to – people with heart failure, or people with atrial fibrillation or ongoing ischaemia or high blood pressure – those patients are already excluded.”
Professor Sindone wrote the section on beta-blockers and survival after myocardial infarction in the 2017 PERMIT network analysis consensus recommendations.
Those recommendations said that once patients reached the first 12 months after a heart attack, they could stop taking beta-blockers if they didn’t have heart failure, hypertension, ischemia or atrial fibrillation.
Cardiologist Professor Tom Marwick said the evidence from the study wasn’t “unequivocal” because it was propensity matched, not a randomised controlled trial, so there were unmeasured cofounders.
For instance, participants at lower risk may have been taken off beta blockers, while those at higher risk may have stayed on the medication, Professor Marwick, director of the Baker Heart and Diabetes Institute, told TMR.
Professor Marwick said previous evidence regarding the effectiveness of beta-blockers after heart attack was “from a different era and a different group of patients”.
“When the original beta blocker studies were done, which is decades ago, there wasn’t an effective revascularisation strategy. People had substantial-sized infarcts and as a consequence, a very significant proportion of people after infarction had left ventricular impairment.
“Now we’re in a completely different era where there’s rapid revascularisation, and the infarct sizes are much smaller.
“The message that we’re getting from this study as well as previous ones of similar design is that in people with preserved left ventricular function and no heart failure, the long-term benefits of beta blockers are probably not very high.”
Professor Marwick said it was important to note that the study excluded people with left ventricular systolic dysfunction and heart failure.
“There’s no question that beta-blockers are beneficial in people with left ventricular dysfunction and heart failure.”
Professor Marwick said patients often discussed dropping some medications at their review one year after having a heart attack.
“The patient’s keen to move on and reduce the number of meds and the beta-blocker is one of the things that people would discuss discontinuing in a low-risk patient, but the guidelines are not specific about that.
“If somebody is fully revascularised and on appropriate treatment, then their level of risk is low, so the return on investment for beta blocking them is pretty small.”
