This post will be updated when more information is available.More news: Surprise! Ariana Grande and 'SNL' Star Pete Davidson Are Engaged
He said Mr Kudlow has been "working so hard" on trade and the economy.
Vice President Mike Pence also tweeted about Mr Kudlow's heart attack.
Kudlow, a former economic adviser to President Ronald Reagan and a Wall Street economist, has played a key role in ongoing trade talks, including disputes with China that led Trump to threaten tariffs.More news: U.S. hits five Russian firms with sanctions, citing cyberattacks
Kudlow, 70, was one of the administration's point men waging war against Canadian Prime Minister Justin Trudeau for "betrayal" on the Sunday shows for Trudeau's vows to stand up against US tariffs.
It was not immediately known when Kudlow suffered the heart attack. Before joining the White House, he had vehementlyopposed the protectionist trade agenda that Trump promoted, but he became a forceful advocate for Trump's policies since joining the administration.
The heart attack comes just days after Kudlow raised eyebrows by claiming Justin Trudeau "stabbed us in the back" after a G7 summit hosted by the Canadian leader ended in acrimony. He left that position in the early 1990s to treat an addiction to alcohol and drugs. His recovery has always been a source of pride for him and his friends, contributing to his optimistic outlook.More news: The Trump administration will stop granting asylum to domestic abuse victims
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