O’Fallon, W. Michael

Background and Purpose —There is scant information available on the incidence of transient ischemic attack (TIA) in a defined population. This study defines incidence rates of first TIA and subtypes of TIA during 1985–1989 and compares the incidence to that obtained from a 1960–1972 cohort study. Methods —Medical records of all residents of Rochester with potential diagnosis of TIA during 1985–1989 were screened to determine whether the case met the criteria for TIA. All available data were used to determine the vascular distribution of the TIA. Average annual age- and sex-adjusted incidence rates were calculated for 1985–1989, and results were compared with incidence rates determined in a Rochester-based 1960–1972 cohort study. Results —Two hundred two cases of first TIA or amaurosis fugax occurred among Rochester residents during 1985–1989. The age- and sex-adjusted incidence rate for any TIA was 68/100 000 population. Incidence of amaurosis fugax was 13/100 000; anterior circulation (cerebral) TIA, 38/100 000; and vertebrobasilar distribution TIA, 14/100 000. Rates were similar to those determined from a 1960–1972 cohort study. Conclusions —The incidence rate of TIA is 41% that of stroke incidence. TIA incidence in Rochester, Minn, is higher than has been previously reported for other sites throughout the world. Although comparison with prior time periods is difficult because of ascertainment issues, it appears that there has been no significant change in TIA incidence since the decade of the 1960s or earlier. This suggests that the most common mechanism for TIA (atherosclerosis) has not changed in prevalence, nor have risk factors leading to this mechanism.

Background and Purpose The purpose of this study was to clarify whether mitral valve prolapse increases the subsequent risk of stroke. Methods A historical cohort study was conducted on 1079 residents of Olmsted County, Minnesota, who had an initial echocardiographic diagnosis of mitral valve prolapse between 1975 and 1989 without prior stroke or transient ischemic attack and who were followed up for first stroke occurrence. Results There was an overall twofold increase in the incidence of stroke among individuals with mitral valve prolapse relative to the reference population (standardized morbidity ratio, 2.1; 95% confidence interval, 1.3 to 3.2). Sex, duration of follow-up from the diagnosis of mitral valve prolapse, or calendar year of initial diagnosis did not modify the association. Within the cohort of patients who were at least 35 years old at diagnosis of mitral valve prolapse, a time-dependent proportional-hazards multivariate model and a person-years analysis revealed that age, ischemic heart disease, congestive heart failure, and diabetes mellitus were important determinants for stroke when person-years of observation after mitral valve replacement were excluded. Among seven persons with mitral valve replacement, three strokes occurred in 24 person-years of follow-up. For those with an auscultatory diagnosis of mitral valve prolapse only as the indication for echocardiography (44%), the risk of stroke relative to the population was 1.0 (95% confidence interval, 0.2 to 2.9); for those with another cardiac diagnosis, the standardized morbidity ratio was 2.5 (95% confidence interval, 1.5 to 4.0). Conclusions Individuals with uncomplicated mitral valve prolapse did not have an increased risk of stroke, although a small increase in the risk may not have been detected.

This is a study of cardiac diseases associated with the 1,382 cases of first cerebral infarction in residents of Rochester, Minn., during 1960-1984. This is a population-based study in Rochester, Minn., for which the medical record-linkage system was used to identify cardiac disease among patients with first cerebral infarction. There were 318 patients (23%) who had at least one major potential cardiac source of emboli. The proportion of patients with a cardiac source of emboli was significantly higher among patients older than age 75 years (29%) than among younger patients (17%). The 30-day stroke recurrence rate among patients with a cardiac source of emboli (2%) was not significantly different than that among those without a cardiac source of emboli (2%). Among patients with a cardiac source of emboli, there was no difference in the probability of stroke at 30 days and at 90 days for those treated or not treated with anticoagulants. During the first 30 days after cerebral infarction, the risk of death in patients with a cardiac source of emboli (23%) was 14 times that of recurrent stroke. The risk of death at 30 days in patients without a cardiac source of emboli was 8%. Significant independent predictors of death (Cox proportional-hazards analysis) were age, prior myocardial infarction, atrial fibrillation present at onset of stroke, congestive heart failure before the stroke, and an age x congestive heart failure interaction. The only significant independent predictors of recurrent stroke were cardiac valve disease and congestive heart failure.

This study evaluated the characteristics and natural history of patients with lacunar (small, deep) cerebral infarcts in a defined population for comparison of these characteristics to those in patients with nonlacunar infarcts. This is a population-based study in Rochester, Minnesota, from 1960 to 1984, that used the medical record-linkage system to identify and characterize patients with cerebral infarction. The age- and sex-adjusted average annual incidence rate of lacunar cerebral infarction was 13.4/100,000 persons, accounting for 12% of all first cerebral infarcts. Temporal trends in incidence rates, stroke recurrence rates, prevalence of diabetes mellitus, and causes of death (given survival for 30 days) for cases of lacunar infarction were not significantly different from those for cases of nonlacunar infarction. Hypertension was found in 81% of patients who had a lacunar infarct and in 70% of patients who had a nonlacunar infarct (p = 0.05). A potential cardiac source of embolism was found in 12% of patients who had a lacunar infarct and in 28% of patients who had a nonlacunar infarct (p = 0.002). Survival was significantly better after a lacunar infarct than after a nonlacunar infarct. Small, deep cerebral infarcts had many of the epidemiological characteristics of other cerebral infarcts but there was a slightly higher frequency of hypertension, significantly lower frequency of a cardiac embolic source, and significantly better survival in patients with lacunar infarction than in those with nonlacunar infarction.

This study is a prospective analysis of the predictive value of diffuse and localized carotid bruit. Patients with asymptomatic carotid bruits are compared with a population-based age- and sex-matched control group known not to have carotid bruit, in regard to subsequent transient ischemic attack, stroke, and death. Each person was followed until death or for 5 years. Among the 566 patients with asymptomatic carotid bruit, the annual stroke rate given survival was 1.5%/yr or 7.5% at 5 years by actuarial analysis. The annual stroke rate given survival for the 428 patients in the population-based cohort was 0.5%/yr or 2.4% at 5 years. Patients with localized carotid bruit were not significantly different from those with diffuse carotid bruits in regard to subsequent cerebral ischemic events (p = 0.11). These data indicate that patients with asymptomatic diffuse or localized carotid bruit are approximately three times more likely to have ischemic stroke than an age- and sex-matched population sample known not to have carotid bruit.