Whisnant, Jack P.

Background and Purpose —There is scant population-based information on functional outcome, survival, and recurrence for ischemic stroke subtypes. Methods —We identified all residents of Rochester, Minnesota, with a first ischemic stroke from 1985 through 1989 using the resources of the Rochester Epidemiology Project medical records linkage system. After reviewing medical records and imaging studies, we assigned patients to 4 major ischemic stroke categories based on National Institute of Neurological Diseases and Stroke Data Bank criteria: large-vessel cervical or intracranial atherosclerosis with stenosis (ATH, n=74), cardioembolic (CE, n=132), lacunar (LAC, n=72), and infarct of uncertain cause (IUC, n=164). We used the Rankin disability score to assess functional outcome and the Kaplan-Meier product-limit method and Cox proportional hazards regression analysis with bootstrap validation to estimate rates and identify predictors of survival and recurrent stroke among these patients. Results —Rankin disabilities were different across stroke subtypes at the time of stroke and 3 months and 1 year later ( P =0.001). LAC was associated with milder deficits compared with other subtypes. Mean follow-up among the 442 patients in the cohort was 3.2 years. Estimated rates of recurrent stroke at 30 days were significantly different ( P <0.001): ATH, 18.5% (95% CI 9.4% to 27.5%); CE, 5.3% (95% CI 1.2% to 9.6%); LAC, 1.4% (95% CI 0.0% to 4.1%); and IUC, 3.3% (95% CI 0.4% to 6.2%). After adjusting for age, sex, and stroke severity, infarct subtype was an independent determinant of recurrent stroke within 30 days ( P =0.0006; eg, risk ratio for ATH compared with CE=3.3, 95% CI 1.2 to 9.3) but not long term ( P =0.07). Four of 25 recurrent strokes within 30 days were procedure-related, each in patients with ATH. Five-year death rates were significantly different ( P <0.001): ATH, 32.2% (95% CI 21.1% to 43.2%); CE, 80.4% (95% CI 73.1% to 87.6%); LAC, 35.1% (95% CI 23.6% to 46.0%); and IUC, 48.6% (95% CI 40.5% to 56.7%). With adjustment for age, sex, cardiac comorbidity, and stroke severity, the subtype of ischemic stroke was an independent determinant of long-term ( P =0.018; eg, risk ratio for ATH compared with cardioembolic=0.47, 95% CI 0.29 to 0.77) but not 30-day survival ( P =0.2). Conclusions —Early recurrence rates for ischemic stroke caused by ATH are higher than those for other subtypes and higher than previous non–population-based studies have reported. Some of the increased risk of early recurrence among patients with ATH may be iatrogenic. Patients with LAC have better poststroke functional status than those with other subtypes. Survival is poorest among those with ischemic stroke with a cardiac source of embolism.

Background and Purpose —There is little population-based information on cerebrovascular events and survival among valvular heart disease patients. We used the Kaplan-Meier product-limit method and the Cox proportional hazards model to determine rates and predictors of cerebrovascular events and death among valve disease patients. Methods —This population-based historical cohort study in Olmsted County, Minnesota, reviewed residents with a first echocardiographic diagnosis of mitral stenosis (n=19), mitral regurgitation (n=528), aortic stenosis (n=140), and aortic regurgitation (n=106) between 1985 and 1992. Results —During 2694 person-years of follow-up, 98 patients developed cerebrovascular events and 356 died. Compared with expected numbers, these observations are significantly elevated, with standardized morbidity ratio of 3.2 (95% CI, 2.6 to 3.8) and 2.5 (95% CI, 2.2 to 2.7), respectively. Independent predictors of cerebrovascular events were age, atrial fibrillation, and severe aortic stenosis. The risk ratio of severe aortic stenosis was 3.5 (95% CI, 1.4 to 8.6), with atrial fibrillation conferring greater risk at younger age. Predictors of death were age, sex, cerebrovascular events, ischemic heart disease, and congestive heart failure, the greatest risk being among those with both congestive heart failure and cerebrovascular events (risk ratio=8.8; 95% CI, 5.8 to 13.4). Valve disease type and severity were not independent determinants of death. Conclusions —The risk of cerebrovascular events and death among patients with valve disease remains high. Age, atrial fibrillation, and severe aortic stenosis are independent predictors of cerebrovascular events, and age, sex, cerebrovascular events, congestive heart failure, and ischemic heart disease are independent predictors of death in these patients.

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 —This study was conducted to determine the risk factors for ischemic stroke in a defined Russian population. Methods —Our data are based on a population-based case-control study of 237 patients with first-ever ischemic stroke and 237 age- and sex-matched controls. Logistic regression methods for matched pairs were used to estimate the relative risk for the variables studied. Results —In a multivariate analysis, hypertension, left ventricular hypertrophy on electrocardiography, ischemic heart disease, mitral valve disease, current cigarette smoking, and high body mass index were significant and independent risk factors for ischemic stroke in this Russian community. Conclusions —The significant risk factors for ischemic stroke in Novosibirsk are similar to those from other populations and cohorts. This study, the first of stroke risk factors in Russia, has implications for clinical practice and the planning of stroke prevention in the population.

Background and Purpose The present study was conducted to investigate the incidence of stroke and 30-day case-fatality rates for stroke in a defined Russian population. Methods This is a population-based study that was established in 1982. All residents of an administratively defined and typical district of Novosibirsk (approximately 150 000 subjects) who had an incident (first-ever) stroke from January 1, 1982, through December 31, 1992, were registered. Results During an 11-year study period, 3406 incident stroke patients were registered, for an overall crude average annual incidence rate of 202/100 000 population. The rates were higher with increasing age and were significantly higher for men than for women. The age- and sex-adjusted annual incidence rate of stroke declined from 271/100 000 in 1982 to 232/100 000 in 1992. Slowing of the decline in stroke incidence was observed after 1988, and stroke incidence increased slightly in 1992. No significant differences in 30-day stroke case-fatality rates were noted from 1982 through 1992, but a slight trend toward decreasing rates was observed after 1988. There was no major change in patient age at stroke onset. Conclusions Stroke incidence rates in Novosibirsk are among the highest in the world. We observed a decline in stroke incidence but little change in 30-day case-fatality rates in Novosibirsk from 1982 through 1992.

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.

Much of the available data on stroke occurrence, service use, and cost of care originated with hospital discharge abstracts. This article uses the unique resources of the Rochester Epidemiology Project to estimate the sensitivity and positive predictive value of hospital discharge abstracts for incident stroke. The Rochester Stroke Registry was used to identify all confirmed first strokes (hospitalized and nonhospitalized) among Rochester residents for 1970, 1980, 1984, and 1989 (n = 364). The sensitivity of discharge abstracts was estimated by following these individuals for 12 months after stroke to determine the proportion assigned a discharge diagnosis of cerebrovascular disease (International Classification of Diseases [ICD] codes 430 through 438.9). The positive predictive value of discharge abstracts was assessed by identifying all hospitalizations of Rochester residents with an ICD code of 430-438.9 in 1970, 1980, and 1989 (n = 377). Events were categorized as incident stroke, recurrent stroke, stroke sequelae, or nonstroke after review of the complete community-based medical record by a neurologist. Only 86% (n = 313) of all first-stroke patients in 1970, 1980, 1984, and 1989 were hospitalized. Of hospitalized patients, only 76% were assigned a principal discharge diagnosis code of 430-438.9. Fatal strokes and those occurring during a hospitalization were less likely to be identified. Among all hospitalizations of Rochester residents in 1970, 1980, and 1989, there were 377 with a principal diagnosis code of 430-438.9. Less than half (n = 177) were determined by the neurologist to be incident stroke; only 60% (n = 225) were either incident or recurrent stroke. Comparison of alternative approaches showed the validity of discharge abstracts was enhanced by increasing the number of diagnoses and excluding codes with poor positive predictive value. This study provides previously unavailable estimates of the sensitivity of stroke-coded hospitalizations for a US community. A model for improving the sensitivity and positive predictive value of discharge abstracts is presented.

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.