One big suburban cardiology practice has been snapped up by a hospital system and another is on the block, deals likely to deliver a defibrillator-like jolt to Chicago's lucrative heart-care market. Midwest Heart Specialists, the state's biggest cardiology practice, with 50 physicians blanketing the west and northwest suburbs, is in sale talks with Advocate Health Care and possibly others, sources say. And last week another cardiology group, Illinois Heart & Vascular, was acquired by Adventist Midwest Health, which will add 15 heart doctors to two of Adventist's four west suburban hospitals. Experts expect deals between cardiology groups and hospitals to multiply amid national health reforms and a crackdown on payments for heart-care services by the federal Medicare program. The feds cut payments for some heart-care tests and services earlier this year. The national reform law passed last spring dangles financial incentives for hospitals and doctors to better integrate care, making it more enticing for private-practice cardiologists to become salaried hospital employees.