Former Polish President and Solidarity trade union leader Lech Walesa is undergoing tests for heart failure and may need a heart transplant, Houston's Methodist Hospital said on Tuesday.

Walesa, 64, arrived Monday night and had tests on Tuesday to determine the extent of his illness and the proper course of treatment, a hospital spokeswoman said.

"We're doing everything we can to make sure he doesn't need a transplant right away," spokeswoman Erin Fairchild said. "Our goal, of course, is to prevent that."

Doctors were planning a minor surgical procedure to implant a pacemaker on Wednesday, Fairchild said. The device automatically sends signals to maintain a steady heartbeat.

She said it was unclear when Walesa, who was awarded the Nobel Peace Prize in 1983 for his leadership of the Solidarity trade union that shook Poland's communist control, would be able to leave the hospital.

"We're going to evaluate how the pacemaker works as well as other test results before we know when he'll go home as well as when he'll come back for followup," she said.

Walesa led workers' rights movements in Poland in the 1970s. Solidarity won Communist government recognition after a 1980 Gdansk shipyard strike but was crushed when martial law was imposed in December, 1981 and Walesa was detained. Though freed in 1982, he spent the next six years in detention or under surveillance by Polish authorities.

Solidarity re-emerged and led the push for democratic elections in 1988, winning power in 1989 when the decades-long communist government collapsed. Walesa was elected post-communist Poland's first president in 1989 and served until voters turned against him in 1995. (Reuters)