Larry Kudlow, economic adviser to President Donald Trump, has had a heart attack and is being treated at Walter Reed Medical Center, according to a tweet sent from the president's Twitter account Monday evening. 

The White House said this evening Kudlow is in "good condition" after experiencing a "mild" heart attack.

The information about Kudlow's heart attack came just minutes before the president was set to meet in an unprecedented summit with North Korean President Kim Jong Un. Kudlow was not part of the entourage that traveled to Singapore with the president.

Kudlow assumed his role as the Director of the National Economic Council in April.

Jim Cramer, founder of TheStreet Inc., and host of CNBC's Mad Money, partnered with Kudlow for four years on a show called Kudlow & Cramer.

Cramer said Monday night, "Larry is a great friend and partner and I wish him well. He has taught me so much about strength and prayer and faith, and I am summoning all of his teachings to help him get back on his feet asap."

When Kudlow, 70, was named as the president's top economic adviser, Cramer wrote on TheStreet, "First, let me distill Larry's philosophy to one word: growth. Larry's the most pro-growth person I have ever met. In our time together we didn't see eye to eye on much, but the glue, what held it altogether, was our affinity for growth -- because growth can cure so much and growth can make our country stronger and more powerful than any other elixir.

He also said Kudlow is "a fantastic speaker and a legendarily congenial and articulate statesman."