Jamie Dimon, the longtime chairman and chief executive of JPMorgan Chase, had an emergency medical procedure on his heart on Thursday, according to a memo sent to bank employees.

Mr. Dimon, 63, underwent successful heart surgery for an “acute aortic dissection,” and he is recovering, said the memo, which was reviewed by The New York Times. He checked himself into a hospital Thursday morning after experiencing chest pains, according to a person familiar with the matter.

An aortic dissection occurs when blood forces its way into a tear in the aorta, the biggest artery in the body, separating its layers or peeling them apart. About two-thirds of people who have an aortic dissection are male, according to the American Heart Association, and those with high blood pressure or high cholesterol may be at greater risk.

While Mr. Dimon is out, the bank will be run by two senior JPMorgan executives, Daniel Pinto and Gordon Smith, the memo said.