BACKGROUND Several studies have demonstrated that women with nonobstructive coronary disease have a high rate of subsequent investigations, rehospitalizations for recurrent chest pain, and repeat coronary angiography. The sex specificity of this finding is unclear. We therefore undertook an evaluation of sex differences in rehospitalization for acute coronary syndrome (ACS) or chest pain in patients with "angiographically normal" coronaries.   
 METHODS A retrospective cohort study using prospectively collected angiographic and clinical data on all patients in British Columbia, Canada, presenting for their first cardiac catheterization with suspected ischemic heart disease but angiographically normal coronaries.   
 RESULTS Among 32,856 patients, 7.1% of men versus 23.3% of women were angiographically normal (P < .001). Among angiographically normal patients, women were older and more likely to present with hypertension, prior stroke, chronic obstructive pulmonary disease, and peripheral vascular disease than men, but Canadian Cardiovascular Society class of angina did not vary by sex. Within 1 year, 1.0% died, (19 women, 18 men, P = .27) and 0.6% had a stroke (13 women, 9 men, P = .91). Readmission to hospital for ACS or chest pain requiring catheterization was significantly higher in women compared to men (adjusted OR 4.06; 95% CI 1.15-14.31).   
 CONCLUSIONS In a contemporary, population-based cohort presenting for cardiac catheterization for suspected ischemia, women with angiographically normal coronaries were >4 times more likely to be readmitted to hospital for ACS/chest pain within 180 days compared to men. The observed sex difference has important social and economic implications and suggests that traditional diagnostic methods may not be optimal for women.
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