John Lechleiter, the longtime chief executive of Eli Lilly, is recovering from successful surgery to repair a dilated aorta, the U.S. drugmaker said on Tuesday.

"Dr. Lechleiter is recovering and will be closely monitored by the medical staff over the next several days," following his surgery on Monday, the Indianapolis company said in a statement.

Lilly Chief Financial Officer Derica Rice, 48, has taken on the additional role of acting CEO during Lechleiter's absence. The company last week said Lechleiter is expected to return to work this summer. Company officials could not immediately be reached on Tuesday.

Lechleiter, 59, had no symptoms of the condition, but learned of it during recent unrelated medical testing, Lilly said. The condition involves ballooning of the large artery that carries blood from the heart to all limbs and other organs, except the lungs.

Surgery is conducted to prevent rupture of the aorta, which can be life threatening.