The researchers, led by Thomas Mooe, M.D., of Norrland University Hospital in Umea, also identified three factors that increase the likelihood of having a heart attack-related stroke: Atrial fibrillation (in which the upper chambers of the heart fail to beat properly so they don't fully empty, allowing blood to pool and clot; if a clot is expelled from the chamber it could lodge in a brain blood vessel and cause a stroke); ST elevation, an abnormality that can be seen on a graphic readout of the heart's electrical activity; and having had a previous stroke, or "brain attack."
"Stroke after a heart attack is an infrequent but important clinical problem," Mooe and his colleagues say. They stress that simply taking aspirin may be enough to reduce further the possibility of having a heart attack-related stroke. However, blood-thinning drugs like heparin and warfarin should be considered for people at a high risk of stroke, particularly individuals with a heart rhythm irregularity called atrial fibrillation.
Mooe and his colleagues examined the medical records of 124 male and female heart attack survivors who had experienced an ischemic stroke -- a stroke caused by inadequate blood flow to the brain -- within a month of their heart attack. They then compared these with records of 124 adult men and women who had survived a heart attack, but had not had a stroke. Both groups were matched for age, sex and year of occurrence.
The 248 individuals were from a population of 310,000 men and women ages 25-74 years, who participated in the MONICA (Monitoring of Trends and Determinants in Cardiovascular Disease) study from 1985 to 1994. Fifty-one percent of the strokes occurred within five days of the onset of heart attack symptoms. Atrial fibrillation that occurred while the patient was in the hospital had the highest potential to predict a stroke after a heart attack.
Seventy-five percent of people who experienced a subsequent stroke were alive 28 days after their heart attack, and 54 percent were alive after one year. Corresponding figures for people without a stroke were 85 percent and 75 percent, respectively.
The scientists say, however, that there appears to be a declining trend in the incidence and rate at which heart attack-related ischemic strokes occur. This trend, they hypothesize, may be due to the more routine use in recent years of aspirin and clot-busting drugs like streptokinase and tissue plasminogen activator, also known as TPA.
Co-authors of the study were: Peter Eriksson, M.D., and Birgitta Stegmayr, Ph.D.
Media advisory: Dr. Mooe can be reached by calling 46 90 785 0000. Reporters may call (214) 706-1173 for a copy of the journal report. (Please do not publish telephone numbers.)