Vanguard Health Systems, the owner of West Suburban Medical Center , is about to be sold, representing yet another shift in ownership for the Oak Park hospital.

Tenet Healthcare Corporation and Vanguard Health Systems, Inc. have signed a definitive agreement whereby Tenet will acquire Vanguard. The pact, which is expected to close before the end of 2013 pending anticipated regulatory approvals, will extend Tenet’s reach into markets like Chicago and Detroit. Vanguard currently has four hospitals. Three of them are located in the western suburbs — West Suburban, Westlake Hospital in Melrose Park and MacNeal Hospital in Berwyn.

The shift is just the latest change in ownership for West Sub which has had a series of owners over the past decade. During that timeframe the hospital has moved from being an independent, non-profit community hospital to a merger with Loyola Medical Center. The merger was later broken up and West Sub returned, for a short while, as an independent. The hospital was then acquired by Resurrection Health Care. While Resurrection did build a needed ER for West Sub, the system’s broader financial problems led to the Oak Park hospital’s sale to the for-profit Vanguard system. Westlake Hospital was also part of that deal.

“This unique strategic transaction will bring together organizations that share a common commitment to providing high quality care and create significant new growth prospects for Tenet,” Trevor Fetter, president and chief executive officer of Tenet, wrote in the press release. “This acquisition will take Tenet into new geographic markets, expand the breadth of our service offerings, diversify our earnings sources and increase the benefits we expect to realize under healthcare reform. We expect additional financial contributions to come from supply costs savings and labor management efficiencies.”

Upon closing, Charlie Martin, Vanguard’s founder, chairman and chief executive officer, will join Tenet’s Board of Directors. Keith Pitts, Vanguard’s vice chairman, will join the Tenet senior management team as vice chairman.

Consolidation in the health care industry is partially a response to the ongoing implementation of national health care reform. The Wall Street Journal has reported that this acquisition is unlikely to be the last by Tenet.