"Abandonment of this type of therapy for post-MI [post-heart attack] patients based upon an observational study is not warranted," he said.
For the time being, the study raises questions, said Dr. Harlan Kumhulz, a professor of medicine, epidemiology and public health at Yale University.
"The question it raises is about how long after having a heart attack should patients remain on beta blockers?" Kumhulz said, noting that beta-blocker patients didn't have better outcomes than the other patients did after the first year. "The study cannot definitively answer that question -- but raises doubts about the need to continue to take them for the rest of a patient's life."
Dr. Lauren Hughes of the ABC News Medical Unit contributed to this report.