sensitive detection of ischemia. stress testing, even if made in time, is not able to guarantee the prevention of symptoms, fainting, or death. stress testing, although more effective than a resting ecg at detecting heart function, is only able to detect certain cardiac properties. the detection of high-grade coronary artery stenosis by a cardiac stress test has been the key to recognizing people who have heart attacks since 1980. from 1960 to 1990, despite the success of stress testing to identify many who were at high risk of heart attack, the inability of this test to correctly identify many others is discussed in medical circles but unexplained. high degrees of coronary artery stenosis, which are detected by stress testing methods are often, though not always, responsible for recurrent symptoms of angina. unstable atheroma produces "vulnerable plaques" hidden within the walls of coronary arteries which go undetected by this test. limitation in blood flow to the left ventricle can lead to recurrent angina pectoris.