OBJECTIVES:We sought to determine the association between patent foramen ovale(PFO), atrial septal aneurysm(ASA), and stroke prospectively in a unselected population sample. BACKGROUND: The disputed relationship between PFO and stroke reflects methodologic weaknesses in studies using invalid controls, unblinded transesophageal echocardiography examinations, and data that are unadjusted for age or comorbidity. METHODS: The use of transesophageal echocardiography to identify PFO was performed by a single echocardiographer using standardized definitions in 585 randomly sampled, Olmsted County(Minnesota) subjects age 45 years or older participating in the Stroke Prevention: Assessment of Risk in a Community(SPARC) study. RESULTS: A PFO was identified in 140(24.3% ) subjects and ASA in 11(1.9% ) subjects. Of the 140 subjects with PFO, 6(4.3% ) had an ASA; of the 437 subjects without PFO, 5 had an ASA(1.1% , two-sided Fisher exact test, p=0.028). During a median follow-up of 5.1 years, cerebrovascular events(cerebrovascular disease-related death, ischemic stroke, transient ischemic attack) occurred in 41 subjects. After adjustment for age and comorbidity, PFO was not a significant independent predictor of stroke(hazard ratio 1.46, 95% confidence interval 0.74 to 2.88, p=0.28). The risk of a cerebrovascular event among subjects with ASA was nearly four times higher than that in those without ASA(hazard ratio 3.72, 95% confidence interval 0.88 to 15.71, p=0.074). CONCLUSIONS: These prospective population-based data suggest that, after correction for age and comorbidity, PFO is not an independent risk factor for future cerebrovascular events in the general population. A larger study is required to test the putative stroke risk associated with ASA. OBJECTIVES: We sought to determine the association between patent foramen ovale (PFO), atrial septal aneurysm (ASA), and stroke prospectively in a unselected population sample. BACKGROUND: The disputed relationship between PFO and stroke educative methodologic weaknesses in studies using invalid controls, METHODS: The use of transesophageal echocardiography to identify PFO was performed by a single echocardiographer using standardized definitions in 585 randomly sampled, Olmsted County (Minnesota) subjects age 45 years or older Participants in the Stroke Prevention: Assessment of Risk in a Community (SPARC) study. RESULTS: A PFO was identified in 140 (24.3%) subjects and ASA in 11 (1.9%) subjects. Of the 140 subjects with PFO, 6 (4.3 of the 437 subjects without PFO, 5 had an ASA (1.1%, two-sided Fisher exact test, p = 0.028). During a median follow-up of 5.1 years, cereb After adjustment for age and comorbidity, PFO was not significantly associated with predictor of stroke (hazard ratio 1.46, 95% confidence interval 0.74 to 2.88, p = 0.28). The risk of a cerebrovascular event among subjects with ASA was nearly four times higher than that in those without those ASA (hazard ratio 3.72, 95% confidence interval 0.88 to 15.71, p = 0.074). CONCLUSIONS: These prospective population- based data suggest that, after correction for age and comorbidity, PFO is not an independent risk factor for future cerebrovascular events in the general population. A larger study is required to test the putative stroke risk associated with ASA.