LONDON — It may not be advisable for patients with a history of myocardial infarction and preserved left ventricular function to discontinue long-term beta-blocker therapy, warn investigators.

In the randomized ABYSS trial, although there was no difference in death, MI, or stroke between patients who discontinued and those who continued taking beta-blockers, those who stopped taking the drugs had a higher rate of cardiovascular hospitalization.

Discontinuation was also associated with an increase in blood pressure and heart rate, without any improvement in quality of life.

“We thought we would be able to withdraw beta-blockers safely and that this would result in improved quality of life, but our trial results suggest this is not the case,” said lead investigator Johanne Silvain, MD, PhD, from Pitié-Salpêtrière University Hospital in Paris, who presented the ABYSS findings here at the European Society of Cardiology (ESC) Congress.

The results, which were simultaneously published online in the New England Journal of Medicine, call into question current guidelines, which suggest that beta-blockers may be discontinued after 1 year in certain patient groups.

Beta-blockers have long been considered the standard of care for patients after MI, but trials showing the benefit of these drugs were conducted before the modern era of myocardial reperfusion and pharmacotherapy, which have led to sharp decreases in the risk for heart failure and for death after MI, Silvain explained.

This has led to questions about the add-on benefits of lifelong beta-blocker treatment for patients with MI and a preserved left ventricular ejection fraction and no other primary indication for beta-blocker therapy.

The ABYSS Trial
To explore this issue, the open-label, non-inferiority ABYSS trial randomly assigned 3698 patients with a history of MI to the discontinuation or continuation of beta-blocker treatment. All study participants had a left ventricular ejection fraction of at least 40%, were receiving long-term beta-blocker treatment, and had experienced no cardiovascular event in the previous 6 months

At a median follow-up of 3 years, the primary endpoint — a composite of death, MI, stroke, and hospitalization for cardiovascular reasons — occurred more often in the discontinuation group than in the continuation group (23.8% vs 21.1%; hazard ratio, 1.16; 95% CI, 1.01 – 1.33). This did not meet the criteria for non-inferiority of discontinuation, compared with continuation, of beta-blocker therapy (P for noninferiority =.44).

The difference in event rates between the two groups was driven by cardiovascular hospitalizations, which occurred more often in the discontinuation group than in the continuation group (18.9% vs 16.6%).

Other key results showed that there was no difference in quality of life between the two groups.

However, 6 months after randomization, there were increases in blood pressure and heart rate in the discontinuation group. Systolic blood pressure increased by 3.7 mm Hg and diastolic blood pressure increased by 3.9 mm Hg. Resting heart rate increased by 9.8 beats per minute.

“We were not able to show the non-inferiority of stopping beta-blockers in terms of cardiovascular events, [but we] showed a safety signal with this strategy of an increase in blood pressure and heart rate, with no improvement in quality of life,” Sylvain said.

“While recent guidelines suggest it may be reasonable to stop beta-blockers in this population, after these results, I will not be stopping these drugs if they are being well tolerated,” he said.

Sylvain said he was surprised that there was not an improvement in quality of life in the group that discontinued beta-blockers. “We are always told that beta-blockers have many side effects, so we expected to see an improvement in quality of life in the patients who stopped these drugs.”

One possible reason for the lack of improvement in quality of life is that the trial participants had been taking beta-blockers for several years. “We may have, therefore, selected patients who tolerate these drugs quite well. Those who had tolerance issues had probably already stopped taking them,” he explained.

In addition, the patient population had relatively high quality-of-life scores at baseline. “They were well treated and the therapies they were taking were well tolerated, so maybe it is difficult to improve quality of life further,” he said.

The REDUCE-AMI Trial
The ABYSS results appear at first to differ from results from the recent REDUCE-AMI trial, which failed to show the superiority of beta-blocker therapy, compared with no beta-blocker therapy, in acute MI patients with preserved ejection fraction.

But the REDUCE-AMI primary endpoint was a composite of death from any cause or new myocardial infarction; it did not include cardiovascular hospitalization, which was the main driver of the difference in outcomes in the ABYSS study, Sylvain pointed out.

“We showed an increase in coronary cases of hospitalization with stopping beta-blockers, and you have to remember that beta-blockers were developed to reduce coronary disease,” he said.

“Slightly Inconclusive”
Jane Armitage, MBBS, University of Oxford, United Kingdom, the ABYSS discussant for the ESC HOTLINE session, pointed out some limitations of the study, which led her to report that the result was “slightly inconclusive.”

The open-label design may have allowed some bias regarding the cardiovascular hospitalization endpoint, she said.

“The decision whether to admit a patient to [the] hospital is somewhat subjective and could be influenced by a physician’s knowledge of treatment allocation. That is why, ideally, we prefer blinded trials. I think there are questions there,” she explained.

She also questioned whether the non-inferiority margin could have been increased, given the higher-than-expected event rate.

More data on this issue will come from several trials that are currently ongoing, Armitage said.

The ABYSS and REDUCE-AMI trials together suggest that it is safe, with respect to serious cardiac events, to stop beta-blocker treatment in MI patients with preserved ejection fraction, writes Tomas Jernberg, MD, PhD, from the Karolinska Institute in Stockholm, Sweden, in an accompanying editorial.

However, “because of the anti-ischemic effects of beta-blockers, an interruption may increase the risk of recurrent angina and the need for rehospitalization,” he adds.

“It is prudent to wait for the results of additional ongoing trials of beta-blockers involving patients with MI and a preserved left ventricular ejection fraction before definitively updating guidelines,” Jernberg concludes.

The ABYSS trial was funded by the French Ministry of Health and the ACTION Study Group. Sylvain, Armitage, and Jernberg report no relevant financial relationships.