St. Louis Rams football coach Mike Martz stepped down as head coach indefinitely on Monday, so he can deal with an illness involving his heart. Rams President John Shaw made the announcement, saying that Martz has been admitted to the hospital to deal with an acute bacterial infection of a heart valve.

Last week, Martz missed two practices to have tests run and at the time, doctors believed that he was suffering from the infection. Martz coached the Rams in Sunday’s 37-31 loss to the Seahawks.

The week before that, he was hospitalized, but doctors originally thought he had a sinus infection.

Shaw said that Martz is expected to remain in the hospital for 4-12 days. Beyond that there is no timetable for his return. In the interim, assistant coach Joe Vitt will take the head coaching duties. He filled in for Martz during practice last week. Vitt’s official title is assistant coach/linebacker’s coach. He came to the Rams last season after spending four seasons with the Chiefs as linebackers coach.