A Post reader recently reported that he had suffered a heart attack three months after having a normal stress test. Because of this experience he asked whether the exam was of any use. Here’s my response to him and others who wonder about it:
Exercise stress testing is generally used to confirm coronary artery disease, determine functional capacity, and estimate prognosis. The technology is about 70 percent to 80 accurate in identifying the presence of obstructive coronary artery disease, depending on the extent and location of the obstructions in the coronary arteries. Combining the ECG portion of the test with some sort of imaging, such as echocardiography or thallium (nuclear) scanning, significantly increases the accuracy of exercise stress testing.
An important point to recognize is that the cause of many heart attacks is ruptured plaque. Prior to rupture, the cholesterol plaque may have produced only a 30 percent or 40 percent narrowing—a level that would not be apparent at a stress test. So the risk of a heart attack can change in a “twinkling” if an insignificant obstruction suddenly ruptures and occludes the entire coronary artery.
Unfortunately, that is likely what happened to the Post reader mentioned above.