Following years of rising revenue and strong profits, the six health systems in the Milwaukee area are on track to spend more than $1.3 billion expanding or building new hospitals. They have spent millions more to buy physician practices, hire physicians, and open new clinics. But all that may be in the past, as the economic downturn has taken its toll on the systems' investment portfolios. It already has led to belt-tightening, forcing the systems to look for projects that could be postponed.