Papon, 89, will have a pacemaker fitted during surgery scheduled for Thursday at the Jean-Rostand hospital in Evry, outside Paris, Francis Vuillemin said in a statement.
"There is a high risk of failure in implanting a pacemaker on such an elderly person," Vuillemin said.
Papon's defense team has put in a request for a presidential pardon for medical reasons.
Vuillemin said Papon, who underwent triple bypass surgery several years ago, had tests earlier this week at the Pitie-Salpetriere Hospital in Paris.
Papon is the highest-ranking official of the pro-Nazi Vichy regime to be convicted of crimes against humanity committed during World War II. His high-profile trial lasted six months, France's longest criminal trial.
He began serving his sentence in October after France's highest court upheld a 1998 conviction for complicity in crimes against humanity committed while he was a high-ranking police official in the Gironde region between 1942-44. He continues to deny any wrongdoing.
Shortly before the final verdict, Papon fled to Switzerland, but was quickly apprehended and brought back to France. He was then briefly hospitalized because of heart trouble.
His lawyers have argued that jail conditions threaten Papon's health.
President Jacques Chirac has the power to issue a pardon for medical reasons that would allow Papon to go free. Requests for such pardons are first studied by the Justice Ministry.
Papon enjoyed a brilliant political career in postwar France, serving first as Paris police chief under then-President Charles de Gaulle, and later as budget minister under President Valery Giscard d'Estaing.
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