More than three years since 52-year-old Patricia Schwaller died of a heart attack, the widower and a pharmaceutical giant are poised to square off in court over whether the former blockbuster painkiller Vioxx caused her demise.

Jury selection is to begin here today in the first Midwest trial over the arthritis medication, which Merck & Co. withdrew in 2004 after research showed it increased the risk of heart attacks and strokes.Both sides and observers expect the Schwaller case to be closely watched to see for the first time how the legal wrangling over Vioxx plays out in America’s heartland — and notably in Madison County, Ill., which in recent years has tried to shed its reputation as a plaintiffs’ paradise in big-money lawsuits.