Hartford HealthCare and Backus Healthcare System have agreed to affiliate, it was announced Friday, growing the size of the Hartford health system and expanding health offerings in eastern Connecticut. The agreement, which is subject to approval by state and federal regulators, outlines how the affiliation would work as Backus becomes a part of Hartford HealthCare. The approval-seeking process is expected to take several months. It calls for the creation of an eastern health region for Hartford HealthCare—which would include New London and Windham counties—with the Backus Health System as the region's central care center.