Rashtriya Janata Dal (RJD) chief Lalu Prasad will undergo cardiac surgery, a doctor said.

"Based on the preliminary (medical) reports, we can now confirm that cardiac surgery is needed," said Vijay D'Silva, medical director of Asian Heart Institute (AHI) here.

"The details of what kind of surgery is needed will be available only after a few pending reports are available," he added.

But he said that Lalu Prasad was "fundamentally a healthy person as can be seen form the intense campaigning he has done" for the August 21 Bihar assembly by-elections.

The 66-year-old leader was on Monday admitted to AHI for what was described as a routine check up and underwent a series of medical tests.

"There is nothing to worry," an AHI spokesperson told scribes on Monday.