New York ? A troublingly high number of U.S. patients who are given angiograms to check for heart disease turn out not to have a significant problem, according to the latest study to suggest Americans get an excess of medical tests.

The researchers said the findings suggest doctors must do better in determining which patients should be subjected to the cost and risks of an angiogram. The test carries a small but real risk — less than 1 percent — of causing a stroke or heart attack, and also entails radiation exposure.

Every year in the United States, more than a million people get an angiogram, in which a thin tube is inserted in the arm or groin and threaded up to the heart to check for blocked arteries that could lead to a heart attack. Dye is injected through the tube to make blockages show up on X-rays.