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" A study of 406 sudden cardiac death patients indicates that they often have symptoms , especially the typical symptom angina pectoris [ chest pain ] for as long as 120 minutes before an arrest , " said study lead author Dr. Dirk Muller , a cardiologist and emergency physician at the Medical Clinic II , Cardiology and Pulmonology , in Berlin . " " The risk of having a cardiovascular event , that is , a heart attack , stroke or needing bypass surgery , or of dying of a cardiovascular cause , was increased , " said study senior author Dr. Joel Kaufman , professor of environmental and occupational medicine and epidemiology at the University of Washington . " The reason for this is not known , but one explanation could be estrogen , " said study co-investigator Dr. Olli Raitakari , chief physician at the Turku University Central Hospital . " We have a long way to prove that it 's a cause-and-effect , but it 's a possibility , " said study co-author Robert H. Silverman , a professor and researcher at the Cleveland Clinic . " How stress hormones act to stun the heart remains unknown , but there are several possible explanations that will be the subject of additional studies , " said study co-investigator and cardiologist Hunter Champion , an assistant professor at Johns Hopkins and its Heart Institute .