Characteristics of inter-arm difference in blood pressure in acute aortic dissection

Background: An inter-arm difference in blood pressure (IADBP) is characteristic of acute aortic dissection (AAD), but the importance of which arm exhibits lower blood pressure (BP) and the mechanism underlying IADBP are not well understood. Methods: We identified consecutive patients with chest and/or back pain and suspected acute cardiovascular disease whose BP had been measured in both arms. We retrospectively compared the characteristics of such patients with AAD (n=93) to those without AAD (non-AAD group, n=122). Addition-ally, we separately compared patients with type A AAD (TAAD group, n=58) or type B AAD (TBAD group, n=35) to the non-AAD group. The characteristics analyzed were patient background and IADBP-related factors, including systolic BP (SBP) in the right arm (R) and left arm (L), and R-L or L-R as IADBP. Computed tomography (CT) findings of AD extending to the brachiocephalic artery (BCA) and/or left subclavian artery (LSCA) were examined in patients with an IADBP. Results: In a comparison of the TAAD group and non-AAD group, the prevalences of R <130 mm Hg (38% vs. 19%, p=0.009), L-R >15 mm Hg (19% vs. 8%, p=0.047), L-R >20 mm Hg (14% vs. 4%, p=0.029) were higher in the TAAD group. Multivariate analysis showed that L-R >15 mm Hg with R <130 mm Hg was independently associated with TAAD (OR 25.97, 95% CI 2.45-275.67, p=0.007). However, IADBP-related factors were not associated with TBAD. AAD patients with L-R >20 mm Hg all had TAAD, and all aortic dissection extended to the BCA just before the right common carotid artery on CT. Conclusions: IADBP was characterized by R<L with low R in TAAD but was not associated with TBAD. (J Nippon Med Sch 2021; 88: 467―474).