Legislative action and passage of measures to amend the health care reform law are certain in the wake of Tuesday's congressional elections in which Republicans regained control of the Senate.

But whether any of those measures will ultimately become law is much less certain, experts say.

Since the passage of the Patient Protection and Affordable Care Act in 2010, the GOP-controlled House of Representatives has passed a slew of ACA-related measures.

Some were sweeping, including several that would have repealed the health care reform law. Others were more narrowly focused. For example, the House earlier this year approved a measure that would raise the number of hours employees would have to work before their employers would be required to offer them health care coverage to avoid a massive financial penalty.

But whether broad or narrow, none of those House-approved bills were considered by the Democrat-controlled Senate, where Majority Leader Harry Reid, D-Nevada, declined to bring the measures up for votes.

With control of the Senate shifting to the GOP in January, Senate Democrat leaders no longer will be able to block consideration of measures, such as those passed by the House, to amend the ACA.

And it is certain that the health care reform law will be in the crosshairs of Senate Republican leaders.

Sen. Mitch McConnell, R-Ky., the current Senate Minority Leader and almost certain to become the new majority leader, “has made it clear that he wants to go after the ACA. This will be an area of intense legislative activity. You can count on it,” said Nicholas Allard, dean of the Brooklyn Law School and a senior partner with Squire Patton Boggs L.L.P. in Washington.

Changes to the ACA likely to be considered by lawmakers in the next congressional session include changing the definition of a full-time employee, repealing an employer-paid “reinsurance” fee used to offset losses of insurers writing coverage in the public insurance exchanges, and repealing an excise tax on providers and administrators of very expensive health care plans.

But whether those or other ACA-related measures ultimately become law is less certain. That is because even though Republicans will take control of the Senate in January, they still will be far short of the two-thirds majority needed to overturn any presidential vetoes.

“The GOP may have control of the House and Senate, but a Democrat is still in the White House — and that Democrat, President Obama, is the father of the health care reform law,” said Randy Abbott, a senior consultant with Towers Watson & Co. in Boston. “Republicans may have a majority in the Senate, but not a veto-proof majority,” he added.