Higher Flow Is Present in Unruptured Arteriovenous Malformations With Silent Intralesional Microhemorrhages

Background and Purpose-Silent microhemorrhage (hemosiderin) has been observed in resected brain arteriovenous malformations (bAVM) tissue and may represent a subgroup at increased risk for clinical hemorrhage. Previous studies suggest that ruptured bAVMs have faster flow and shorter mean transit time of contrast in blood vessels than unruptured bAVMs. We hypothesized that flow would be faster in unruptured AVMs with hemosiderin compared with those without hemosiderin. Methods-We selected unruptured, supratentorial bAVMs >3.5 cc with pathology specimens. Hemodynamic features were evaluated using color-coding angiography, including contrast mean transit time of AVM nidus, time to peak (TTP) of feeding artery (FA) and draining vein (DV), and the ratio (TTP DV/FA). Characteristics of 9 cases with hemosiderin and 16 without hemosiderin were compared using 2-sample t tests and Fisher exact tests. Results-No difference in FA TTP and DV TTP was observed between groups. However, cases with hemosiderin had significantly shorter mean transit time compared with those without hemosiderin (1.11 +/- 0.28 versus 1.64 +/- 0.55 seconds; P=0.013) and a lower ratio of DV TTP/FA TTP (1.48 +/- 0.32 versus 1.94 +/- 0.61; P=0.045). Presence of venous varix was significantly associated with hemosiderin (P=0.003). No other clinical or angioarchitectural factors were associated with hemosiderin. Conclusions-Shorter mean transit time through the AVM nidus, lower DV TTP/FA TTP, and the high prevalence of venous varices suggests that high flow is an important feature of unruptured bAVMs with hemosiderin.