According to Medicare records, more than half of the people who undergo angioplasty to clear blocked arteries are not given the recommended cardiac stress test before the procedure. Stress tests--in which a walk on a treadmill is done to test heart function--help doctors separate the patients who will benefit from procedures such as angioplasty or stenting from those who won't. But in study of 24,000 people who underwent non-emergency angioplasty procedures, just 44 percent of patients were...