Introduction: Cerebral arteriovenous malformation (AVM) hemodynamics is important in AVM evaluation and management. We measure flow volume rate, flow velocity, pulsatility index (PI), and resistance index (RI) in AVM feeders using quantitative magnetic resonance angiography (QMRA).

Methods: Records of patients with AVMs evaluated at our institution between 2007-2014 and with flows obtained before treatment using QMRA were retrospectively reviewed. Flow volume rate and flow velocity were measured in primary arterial feeders (anterior cerebral artery, A2 segment; middle cerebral artery, M1 segment; posterior cerebral artery, P2 segment) and compared to their contralateral counterparts. PI = [(systolic – diastolic flow velocity)/mean flow velocity] and RI = [(systolic – diastolic flow velocity)/systolic flow velocity] were calculated for each feeder and compared to the normal contralateral vessel. Relationship between PI, RI and AVM clinical and angioarchitectural features were also assessed.

Results: 72 patients with 98 feeder arteries were included. Cohort characteristics are summarized in the Table. Among all feeders, mean flow volume rate (332.3 vs. 121.6 mL/min, P<0.001) and flow velocity (46.1 vs. 25.8 cm/s, P<0.001) were significantly higher and mean PI (0.20 vs. 0.27, P<0.001) and RI (0.18 vs. 0.23, P<0.001) were significantly lower than in normal contralateral vessels (Figure 1). Similar results were obtained among each vessel type (Figure 2). There was no significant association of PI and RI with hemorrhagic presentation (P=0.64,0.80, respectively), exclusive deep venous drainage (P=0.75,0.11), venous stenosis (P=0.42,0.70), single draining vein (P=0.91, 0.90), or deep location (P=0.32,0.78).

Conclusions: PI and RI can be measured using QMRA and are significantly lower in AVM arterial feeders compared to normal vessels, thereby resulting in significantly higher flow volume rates and flow velocities in feeder vessels. Although we found no significant correlation between PI, RI, and AVM angioarchitectural characteristics thought to be associated with increased hemorrhage risk, future studies with larger sample sizes may better elucidate this relationship.

Patient Care: Our study furthers our understanding of AVM hemodynamics and attempts to correlate increased pulsatility and resistance indices in AVM feeder vessels with AVM features associated with increased hemorrhage risk. This correlation may yield pulsatility and resistance thresholds measured using QMRA that can guide and tailor the management of AVMs by possibly predicting hemorrhage risk.

Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the difference between pulsatility and resistance indices in AVM feeder arteries and normal contralateral vessels, 2) Explain how these differences in pulsatility and resistance indices impact AVM flow volume rate and flow velocity, and 3) Understand the relationship between AVM feeder vessel pulsatility and resistance indices and AVM features associated with increased hemorrhage risk.

References: 1. Lindegaard K-F, Grolimund P, Aaslid R, Hornes H. Evaluation of cerebral AVMs using transcranial Doppler ultrasound. J Neurosurg. 1986;65:335-344. 2. Stapf C, Mast H, Sciacca RR, Choi JH, Khaw AV, Connolly ES, et al. Predictors of hemorrhage in patients with untreated brain arteriovenous malformations. Neurology. 2006;66:1350-1355.