Sen. Bernie Sanders released letters from his primary physician and two cardiologists on Monday stating that the 2020 candidate "has the mental and physical stamina to fully undertake the rigors of the Presidency."

Why it matters: The 78-year-old Sanders has faced questions about his health in the wake of a medical procedure he had after suffering a heart attack in October. Sanders included his health history and results from recent lab tests in the release.

What they're saying:

"You are in good health currently and you have been engaging vigorously in the rigors of your campaign, travel, and other scheduled activities without any limitation," wrote congressional physician Brian P. Monahan.

"Mr. Sanders is more than fit enough to pursue vigorous activities and an occupation that requires stamina and an ability to handle a great deal of stress," wrote Philip A. Ades, director of cardiac rehabilitation at University of Vermont Medical Center.

"I see no reason he cannot continue campaigning without limitation and, should he be elected, I am confident he has the mental and physical stamina to fully undertake the rigors of the Presidency," wrote Martin M. LeWinter, Sanders' personal cardiologist.

Read the letters here.

Go deeper: Bernie Sanders has more steady support in Iowa than any other top candidate