Kudlow's condition wasn't immediately released by Walter Reed National Military Medical Center in Bethesda, Maryland. "He is now in Walter Reed Medical Center".
Kudlow, the director of the National Economic Council, had joined Trump last week in Canada for what became a contentious meeting of the Group of Seven world leaders.
President Donald Trump says his top economic adviser, Larry Kudlow, has suffered a heart attack.
Kudlow had worked as a White House budget aide in the Reagan administration, and had also been an informal advisor to the 2016 Trump campaign.
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After Mr. Trudeau reiterated at the G7 on Saturday that Canada would impose retaliatory tariffs in response to Mr. Trump's metal levies - and the President accused Mr. Trudeau of being "weak and dishonest" - Mr. Kudlow disparaged the Prime Minister in surprisingly personal terms. On Sunday, Kudlow said on CNN's "State of the Union" that Canadian Prime Minister Justin Trudeau "really kind of stabbed us in the back" after criticizing USA tariffs on imported steel and aluminum and Trump's positions on trade in a news conference following the summit.