He carried a message from West Bengal Chief Minister Mamata Banerjee wishing him speedy recovery.
Sen was admitted to the hospital yesterday following a cerebral attack, party sources said.
The former West Bengal Industry minister fell sick at his residence in Salt Lake here yesterday and was immediately rushed to a hospital.
The 67-year-old Marxist leader, who had won the Burdwan South Assembly seat in 2006 and 2001 state Assembly elections, lost to his Trinamool Congress rival in 2011.