Fig. 2.

Two patients with severe LV4 stenosis. For the first patient with severe LV4 stenosis, the right vertebral artery was hypoplastic and terminated at the right PICA (a). Both posterior communicating arteries were nonfunctional; preintervention FF was 0.56, and the translesional Pa-Pd gradient was 24 mm Hg (b). Another patient with similar severe LV4 stenosis (c), with bilateral functioning posterior communicating arteries providing good collateral supply; preintervention FF was 0.94, and the translesional Pa-Pd gradient was 4 mm Hg (d). The yellow tracing corresponds to Pd, and the red tracing corresponds to Pa. Colors refer to the online version only.