BackgroundClinical characteristics and treatment outcomes of acute type A aortic dissection with D‐dimer elevation have not been clarified.Methods and ResultsD‐dimer was measured preoperatively within 24 hours of symptom onset in 262 patients with acute type A aortic dissection. The median (and interquartile range) admission D‐dimer concentration in our total patient group was 26.7 (8.3–85.9) μg/mL. Median (interquartile range) D‐dimer concentrations were 5.0 (2.6–18.0) μg/mL for complete false lumen thrombosis (n=33), 60.9 (19.4–160.4) μg/mL for partial thrombosis (n=81), 26.5 (10.0–70.6) μg/mL for a patent false lumen (n=131), and 8.7 (3.2–26.9) μg/mL for ulcerlike projection (n=17) (P<0.01). With a D‐dimer concentration of ≤8.3 μg/mL representing the lower quartile, we then investigated predictors of a low D‐dimer level. Multivariate analysis showed dissection limited to the ascending aorta (P<0.01; odds ratio, 9.81) or descending aorta (P<0.01; odds ratio, 7.68), a completely thrombosed false lumen (P<0.01; odds ratio, 4.02), and absence of brain ischemia (P=0.013; odds ratio, 4.74) to be predictors of the lower D‐dimer concentration. Compared with patients with a low D‐dimer concentration (≤8.3 μg/mL, n=66), patients with a D‐dimer concentration >8.3 μg/mL (n=196) had a reduced preoperative platelet count and increased operation time and transfusion volume. In‐hospital mortality was elevated in this group (1.5% versus 11.2%; P=0.031), although 7‐year survival did not differ for hospital survivors (lower versus higher, 93.1% versus 79.1%; P=0.21).ConclusionsD‐dimer concentrations are strongly influenced by the extent of dissection and false lumen status. Operative risks are increased in patients with a relatively high D‐dimer concentration.